I have just posted a video snippet of my lathe in action at an event earlier this year.
I have other video of the lathe being used, but this is a bit more of general interest, perhaps.
If you haven't already read it, there are words and pictures about its construction in some earlier posts, starting with this one.
Friday, June 25, 2010
Sunday, May 30, 2010
Cheeses on a plate
While I was building the bells for the next two shawms, I had an interruption. Two friends had been getting around as a couple for a few years and decided to make it official and get married. All well and good, so far. However, they wanted something different for their wedding reception.
Lindsay sent me an URL and asked "Could you make something like this, for our reception?". "Something like this" was a tier of platters 3 or 4 levels high, supporting a range of cheeses and other goodies. I had not done anything like that before, but technically, there did not seem to be any obstacles, so I said "Yes".
My thought was to find some suitable wood through my local network of contacts, and from this, cut sections of trunk or branch to form the platters. I was not sure about the strength of the thin slabs and whether these would manage the stresses. However, if this proved to be a problem I could always use a reinforcing layer of plywood out of sight underneath to hold things together.
So, to find some wood. My initial enquiries did not turn up anything - this was July (local midwinter) and the wedding was in October. I was starting to think of a backup plan of creating a composite from smaller wood, but this would not have a external bark layer, which had a nice visual effect.
And then, the breakthrough: a colleague asked me if I would be interested in a plum tree that he wanted felled. Definitely. Some short while later, after some chainsaw work, I had a 400mm trunk section and plenty of 150-200mm limbs.
By now it was August, and the wood was green. How to dry it as quickly as possible without ruining it? I cut about twice as many slabs as I expected to need (allowing for spoilage), and stacked these with folded newspapers between them in a mild dry place.
For the next three weeks, I cycled the newspaper layers with dry replacements every day and progressively wicked the moisture out. Stacking the slabs may also have helped reduce buckling (I think). No photos of this, sorry. My attention was elsewhere at the time.
It was very obvious after the first week that the slabs were going to split as they dried. I made the best of this by making starter cuts to encourage the splitting to happen where it was manageable.
Once the slabs were dry enough to usefully work, before anything else, I had to deal with the splits. I chose four slabs to be the mainstay pieces, and used a fine saw and wide chisel to clean up the splits to be pretty straight. This left open segments of 30-50 degrees arc. From the unused slabs, I cut segments to match the gaps. However, thinking the matter through, I could see that cutting segments that would fit closely into the gaps left by splitting was not going to be practical.
This sketch shows the sequence I used to add a wedge segment into a split slab.
The virtue of this method is that, at every stage of the jointing, both ends of each join are accessible, and each join is an essentially straight cut, which means that it can be dressed by running a saw between the joint faces a few times, and cleaning up with a wide chisel before the glue goes in.
In this close up, you can see the three way join on the far side of this slab. Using Gorilla Glue, which is both strong and somewhat space filling, the final joint looks pretty tidy when dressed up. Since the donor slab for the inserted segment is from an adjacent slice from the branch, the rings and bark could be arranged to be very similar to the host piece.
Here is my intended final arrangement. I had the platters pretty much sorted out, but had nothing done for the upright pillars. Consulting my stock of wood, I found a piece of birch which had been windfall in a local city park a year or so earlier, which could be made to yield blanks for two of the pillars, but not enough for the third pillar as a single piece.
Here are the slabs doing a bit of a photo-opportunity, with jars and whatever to get roughly the desired spacing.
Interesting to note the difference in the colour of the slabs. The cut slabs quickly turned this deep apricot colour as they dried, but the inner wood shows up really pale once it is dressed flat again. I guess that this is oxidised starch or something similar.
The first two pillars turned up easily enough, although this piece of wood didn't seem to be the best of the bunch - the grain was not as close as other parts from the same tree. Also, possibly not helped by me being in a little bit of a rush, since the handover date was starting to loom disturbingly close.
Here are the dressed slabs doing a trial fit with the first pillar. The central pillar supporting the top slab is also there, slimmer than I had first thought would be necessary. You might recognise the temporary spacer in the middle background as one of the bell sections for the shawms, described in other postings
There wasn't enough good wood to make the third pillar in one piece. In the end, I made it in three parts: lower half, top stem and top rest. The assembled pillar was not quite as true as the others, but looked perfectly good enough in the final assembly.
Putting some coats of shellac on them certainly diverted attention from any vagaries of manufacture.
I finally had the slabs to a state that was close enough to ready for varnishing. I did not want to use a modern polyurethane since it would not have time to cure enough to be sure that it would not taint the food on the platters. Also, I rather liked the look and feel of the shellac I had been using for other work, and I knew that it was tasteless and very food safe.
A good choice, as it turned out. After a generous coating on the bark sections, these were transformed from rough dull finish to a subtly gleaming shiny finish that looked very good. After that, it was almost an anticlimax to varnish the dressed sections of wood, but the pale faces of plum became rich golden coloured surfaces.
And here is the final assembly, just prior to be taken apart for delivery.
Possibly being overcautious, but I had visions of the pillars possibly spreading under the load and creating An Incident at the wedding, so I slipped in a loop of waxed thread around the tops of the pillars to pull them into place. You can just see the thread around the tops of the pillars.
So to the day of the wedding. It was at a picturesque small church on Banks peninsula, with views looking out East over the Pacific Ocean. The weather was brilliant, and the site was beautifully sheltered from any wind of consequence.
Here is the platter set, loaded and ready for action.
This was an interesting enough project, but doing it again would be less inspiring, since the element of surprise would not be there.
Lindsay sent me an URL and asked "Could you make something like this, for our reception?". "Something like this" was a tier of platters 3 or 4 levels high, supporting a range of cheeses and other goodies. I had not done anything like that before, but technically, there did not seem to be any obstacles, so I said "Yes".
My thought was to find some suitable wood through my local network of contacts, and from this, cut sections of trunk or branch to form the platters. I was not sure about the strength of the thin slabs and whether these would manage the stresses. However, if this proved to be a problem I could always use a reinforcing layer of plywood out of sight underneath to hold things together.
So, to find some wood. My initial enquiries did not turn up anything - this was July (local midwinter) and the wedding was in October. I was starting to think of a backup plan of creating a composite from smaller wood, but this would not have a external bark layer, which had a nice visual effect.
And then, the breakthrough: a colleague asked me if I would be interested in a plum tree that he wanted felled. Definitely. Some short while later, after some chainsaw work, I had a 400mm trunk section and plenty of 150-200mm limbs.
By now it was August, and the wood was green. How to dry it as quickly as possible without ruining it? I cut about twice as many slabs as I expected to need (allowing for spoilage), and stacked these with folded newspapers between them in a mild dry place.
For the next three weeks, I cycled the newspaper layers with dry replacements every day and progressively wicked the moisture out. Stacking the slabs may also have helped reduce buckling (I think). No photos of this, sorry. My attention was elsewhere at the time.
It was very obvious after the first week that the slabs were going to split as they dried. I made the best of this by making starter cuts to encourage the splitting to happen where it was manageable.
Once the slabs were dry enough to usefully work, before anything else, I had to deal with the splits. I chose four slabs to be the mainstay pieces, and used a fine saw and wide chisel to clean up the splits to be pretty straight. This left open segments of 30-50 degrees arc. From the unused slabs, I cut segments to match the gaps. However, thinking the matter through, I could see that cutting segments that would fit closely into the gaps left by splitting was not going to be practical.
The virtue of this method is that, at every stage of the jointing, both ends of each join are accessible, and each join is an essentially straight cut, which means that it can be dressed by running a saw between the joint faces a few times, and cleaning up with a wide chisel before the glue goes in.
In this close up, you can see the three way join on the far side of this slab. Using Gorilla Glue, which is both strong and somewhat space filling, the final joint looks pretty tidy when dressed up. Since the donor slab for the inserted segment is from an adjacent slice from the branch, the rings and bark could be arranged to be very similar to the host piece.
Here is my intended final arrangement. I had the platters pretty much sorted out, but had nothing done for the upright pillars. Consulting my stock of wood, I found a piece of birch which had been windfall in a local city park a year or so earlier, which could be made to yield blanks for two of the pillars, but not enough for the third pillar as a single piece.
Interesting to note the difference in the colour of the slabs. The cut slabs quickly turned this deep apricot colour as they dried, but the inner wood shows up really pale once it is dressed flat again. I guess that this is oxidised starch or something similar.
Here are the dressed slabs doing a trial fit with the first pillar. The central pillar supporting the top slab is also there, slimmer than I had first thought would be necessary. You might recognise the temporary spacer in the middle background as one of the bell sections for the shawms, described in other postings
There wasn't enough good wood to make the third pillar in one piece. In the end, I made it in three parts: lower half, top stem and top rest. The assembled pillar was not quite as true as the others, but looked perfectly good enough in the final assembly.
Putting some coats of shellac on them certainly diverted attention from any vagaries of manufacture.
I finally had the slabs to a state that was close enough to ready for varnishing. I did not want to use a modern polyurethane since it would not have time to cure enough to be sure that it would not taint the food on the platters. Also, I rather liked the look and feel of the shellac I had been using for other work, and I knew that it was tasteless and very food safe.
A good choice, as it turned out. After a generous coating on the bark sections, these were transformed from rough dull finish to a subtly gleaming shiny finish that looked very good. After that, it was almost an anticlimax to varnish the dressed sections of wood, but the pale faces of plum became rich golden coloured surfaces.
Possibly being overcautious, but I had visions of the pillars possibly spreading under the load and creating An Incident at the wedding, so I slipped in a loop of waxed thread around the tops of the pillars to pull them into place. You can just see the thread around the tops of the pillars.
Here is the platter set, loaded and ready for action.
This was an interesting enough project, but doing it again would be less inspiring, since the element of surprise would not be there.
More Shawms - really about tuning, this time
I was going to run the post on staples and tuning together, but the stuff on tuning was taking too long to come to me, so now they are split into separate posts.
Remembering having tuned the first shawm, I was in a mixed state of mind about doing this next pair. On one hand, I had a working reference for where holes should pretty much be, and I knew that mistakes were almost certainly not terminal. On the other hand, I was not completely impressed with the playability of the first shawm, and wanted to make the next ones better, as far as tinkering with the tuning would allow.
For practical reasons, I planned to continue to use bassoon reeds, and the staples had been designed on this basis, although I was playing the first shawm enough by then to get a feeling that a bassoon reed was not the ideal form.
I took measurements off the first shawm to where the holes were, using the end of the staple as a datum rather than using the end of the bell as I had done for the first one. In retrospect this was an obvious thing to do, but it does rather require that you have a working unit to measure, which had not been the case for the first shawm.
These are the numbers. If you are making a shawm, treat these as starting points only, and be prepared to fiddle. All dimensions are in millimetres, and the holes number from the top down.
A pair of dimensions for a hole mean that it is somewhat elliptical, and these are the lengths of the axes. I drilled the pilot holes in at right angles to the axis, but several holes, no. 4 in particular, have had the inner part of the hole angled in the direction of the reed. This was a compromise between keeping the outer holes in a place where fingers can readily reach it, while getting an acceptable pitch without a huge hole (which would be more difficult to cover).
The first placement of the holes is best done in a single session using the same reed. This should not take more than two hours or so. Don't tinker with the reed too much, other than getting it sounding sufficiently well over the first octave range of the working shawm that you do have. If you don't have a working shawm, this is harder to do...
Since it was never going to get easier, I sealed the inside of the bore by plugging the narrow end and pouring in a measure of thin shellac, and rotating the instrument to thoroughly wet the inside of the bore. Then a basic coat on the outside to avoid marking the wood with grubby fingers during tuning.
I set up a template in a CAD program of where the finger holes should be, and printed a 1:1 overlay. With this taped on in the right place, putting the pilot holes in becomes a doddle.
Here is a shot of the second of the pair with the template taped on and tape markers for the resonators and tuning holes near the foot. Holes are bored straight through the paper template, and it can be rubbed out of the way where not wanted with a gentle application of a rasp.
The hole positions have been rotated around in an bid to improve the fingering of the right hand on the more widely spaced lower holes. Compared to other factors affecting tuning, this has next to no effect.
The left hand shawm is essentially complete, and you will see that the number 2 hole has been remodelled with wood filler.
Tuning works from the bottom up, so the resonator holes went in first (I have since read that these are more important than I first realised, and there will be much more about this in a later post). Then the tuning holes, which set the bottom note "all fingers down" pitch. Some messing around here will be needed to get a reasonable "C". "Reasonable" means something close to a C for wind pressures that the reed and player can comfortably handle. This amount of wind pressure becomes the amount of puff that should be used to tune the remaining notes, if the instrument is to be usefully playable.
Here is the first of these two shawms, close to complete in tuning, obviously before I reworked the no. 2 hole. All the vital tuning tools are to hand: a selection of twist drills from 4.0 to 8.0mm in 0.5mm steps (out of the picture to the right), round and half-round needle files for cleaning up the inside ends of the holes where they enter the bore, water capsule to keep the reed wet while the next hole is bored (near the bell on the left), staple (out of harm's way at the top), and a little electronic keyboard as a pitch reference (out of frame to the left).
It's important that the holes have clean edges, particularly where they enter the bore. When a hole is first drilled, there are usually whiskers at the bottom end, which are pushed back where they are difficult to reach from the outside. I dealt to these with a rod of 6mm steel which has the end ground to a 60 degree angle and the sharp edge of this honed and stropped. By running this rod in from one end or the other, it becomes quite easy to either trim the whiskers off directly with the cutting edge, or to push them across the hole, where they can be cleaned off with a small sharp file from the outside.
When I drill a new finger hole, the rough tuning is done against the keyboard reference, but the final tuning is done against the lower holes already cut, by playing an ascending scale and tuning the new hole so that its note sits comfortably in the scale with a similar intonation to the lower holes.
Small details: when I tuned the first of the second set of shawms, I would spin the twist drills in the forward direction when drilled the holes. All good, but it would leave an untidy edge on the outer end of the hole. I treated all these by shaping a small depression across each hole (visible in the photo above). Visually this was not altogether good.
For the tuning of the second of the shawms, I would spin the twist drills in the reverse direction when starting the hole. The trailing edge of the twist drill is still sharp enough to cut the wood well enough, but leaves a cleaner edge to the hole. The remainder of the hole was cut with the drill spinning forwards. This is no problem to do with most electric drills. The result is a cleaner hole, with no need for an extra depression, as you can see here.
I can't say that it makes any real difference in the feel of the instrument, but it looks better.
Finally, here they all are, together. As you can see, the later shawms have slightly more compact bells than the first one, but have much more sleek lines, and generally look slinkier.
Musically, they are much of a muchness, and playability on any day depends much more on how the reed is feeling than anything else.
From this, I am deducing that I have done as much refining of the shape as is worth doing at the moment.
The next area for improvement is in the reed. This is not an area that I know a great deal about, and I will need to consult and research.
The new shawms have gone to homes in the Barony of Ildhafn (Auckland, New Zealand), and their new owners will be coming to terms with getting good sounds from them.
To be continued.
Remembering having tuned the first shawm, I was in a mixed state of mind about doing this next pair. On one hand, I had a working reference for where holes should pretty much be, and I knew that mistakes were almost certainly not terminal. On the other hand, I was not completely impressed with the playability of the first shawm, and wanted to make the next ones better, as far as tinkering with the tuning would allow.
For practical reasons, I planned to continue to use bassoon reeds, and the staples had been designed on this basis, although I was playing the first shawm enough by then to get a feeling that a bassoon reed was not the ideal form.
I took measurements off the first shawm to where the holes were, using the end of the staple as a datum rather than using the end of the bell as I had done for the first one. In retrospect this was an obvious thing to do, but it does rather require that you have a working unit to measure, which had not been the case for the first shawm.
These are the numbers. If you are making a shawm, treat these as starting points only, and be prepared to fiddle. All dimensions are in millimetres, and the holes number from the top down.
| Hole number | Distance from staple | Diameter |
| 1 | 111 | 4.1 |
| 2 | 165 | 7.3 |
| 3 | 184 | 7.3 |
| 4 | 236 | 8.0x7.7 |
| 5 | 274 | 7.5 |
| 6 | 303 | 7.6 |
| 7 | 337 | 7.4x7.7 |
| Tuning (2 holes) | 416 | 8.3x8.7+7.3x7.9 |
| Resonators (2 holes) | 485 | 7.0+7.0 |
A pair of dimensions for a hole mean that it is somewhat elliptical, and these are the lengths of the axes. I drilled the pilot holes in at right angles to the axis, but several holes, no. 4 in particular, have had the inner part of the hole angled in the direction of the reed. This was a compromise between keeping the outer holes in a place where fingers can readily reach it, while getting an acceptable pitch without a huge hole (which would be more difficult to cover).
The first placement of the holes is best done in a single session using the same reed. This should not take more than two hours or so. Don't tinker with the reed too much, other than getting it sounding sufficiently well over the first octave range of the working shawm that you do have. If you don't have a working shawm, this is harder to do...
Since it was never going to get easier, I sealed the inside of the bore by plugging the narrow end and pouring in a measure of thin shellac, and rotating the instrument to thoroughly wet the inside of the bore. Then a basic coat on the outside to avoid marking the wood with grubby fingers during tuning.
Here is a shot of the second of the pair with the template taped on and tape markers for the resonators and tuning holes near the foot. Holes are bored straight through the paper template, and it can be rubbed out of the way where not wanted with a gentle application of a rasp.
The hole positions have been rotated around in an bid to improve the fingering of the right hand on the more widely spaced lower holes. Compared to other factors affecting tuning, this has next to no effect.
The left hand shawm is essentially complete, and you will see that the number 2 hole has been remodelled with wood filler.
Tuning works from the bottom up, so the resonator holes went in first (I have since read that these are more important than I first realised, and there will be much more about this in a later post). Then the tuning holes, which set the bottom note "all fingers down" pitch. Some messing around here will be needed to get a reasonable "C". "Reasonable" means something close to a C for wind pressures that the reed and player can comfortably handle. This amount of wind pressure becomes the amount of puff that should be used to tune the remaining notes, if the instrument is to be usefully playable.
It's important that the holes have clean edges, particularly where they enter the bore. When a hole is first drilled, there are usually whiskers at the bottom end, which are pushed back where they are difficult to reach from the outside. I dealt to these with a rod of 6mm steel which has the end ground to a 60 degree angle and the sharp edge of this honed and stropped. By running this rod in from one end or the other, it becomes quite easy to either trim the whiskers off directly with the cutting edge, or to push them across the hole, where they can be cleaned off with a small sharp file from the outside.
When I drill a new finger hole, the rough tuning is done against the keyboard reference, but the final tuning is done against the lower holes already cut, by playing an ascending scale and tuning the new hole so that its note sits comfortably in the scale with a similar intonation to the lower holes.
Small details: when I tuned the first of the second set of shawms, I would spin the twist drills in the forward direction when drilled the holes. All good, but it would leave an untidy edge on the outer end of the hole. I treated all these by shaping a small depression across each hole (visible in the photo above). Visually this was not altogether good.
I can't say that it makes any real difference in the feel of the instrument, but it looks better.
Musically, they are much of a muchness, and playability on any day depends much more on how the reed is feeling than anything else.
From this, I am deducing that I have done as much refining of the shape as is worth doing at the moment.
The next area for improvement is in the reed. This is not an area that I know a great deal about, and I will need to consult and research.
The new shawms have gone to homes in the Barony of Ildhafn (Auckland, New Zealand), and their new owners will be coming to terms with getting good sounds from them.
To be continued.
Friday, May 21, 2010
More Shawms - staples and tuning
The staple is the thing what holds the reed, and launches its sound down the bore. In these shawms, I made the staples quite separate from the body, so that I could tinker with construction details and make mistakes without writing off a lot of work.
I have not seen this arrangement in any old images or modern reconstructions of shawms, but there is no modern construction technique required, so it could have been used in period.
Remember the kumihimo bobbins from earlier? Never mind. Here they are again, with one end turned down to shawm size (about 30mm diameter), and the unwanted end removed and a rebate turned in the body which is now about 15mm diameter. There's also a 3mm hole through the middle down the drill press using the flat end as a reference (which still managed to emerge slightly off-centre, grumble).
The guts of the staple is a metal tube. I made this one by wrapping thin copper sheet around a 4mm file. One end needs to have a taper in it to match that of the reeds being used. I am using bassoon reeds, in the absence of anything better (more on this later), and I made a mandrel to match the reeds' taper by filing down a steel bolt in the drill press.
The other end of the tube needs to match the bore of the body reasonably well, so that there not too much discontinuity between the staple and the bore.
These are conflicting requirements, and are not easily met in a single piece of tube - well, not one that I can readily make, anyway. I made these staples in two parts, each with the requisite taper, or lack of it.
The two pieces of rolled copper are sprung together, heated in a soft gas flame and a small amount of solder flowed in to hold them. The trick is to keep the amount of solder "small", i.e., put on what looks like an inadequate amount and trust that it will flow all the way to the end of the seam.
With a 16mm spade bit, it was the work of only a minute or two to form the socket in the top end of the body of the shawm.
With a serving of linen, generously dosed with archers' wax (mixture of beeswax and rosin - sticky stuff), the staple is ready to fit, as seen here. The shawm and staple seem to have acquired a coat of shellac since the last photo, as well.
The straight part of the staple tube is a snuggish fit inside the bore of the shawm. I "glued" the tube into the body of the staple with some thick shellac, which took rather longer to set than I had expected. If I use this staple design again, I would use straight rosin or pitch or even hot-melt glue to fasten the tube.
The next step is tuning the shawms, to be told in the next post.
I have not seen this arrangement in any old images or modern reconstructions of shawms, but there is no modern construction technique required, so it could have been used in period.
Remember the kumihimo bobbins from earlier? Never mind. Here they are again, with one end turned down to shawm size (about 30mm diameter), and the unwanted end removed and a rebate turned in the body which is now about 15mm diameter. There's also a 3mm hole through the middle down the drill press using the flat end as a reference (which still managed to emerge slightly off-centre, grumble). 
The other end of the tube needs to match the bore of the body reasonably well, so that there not too much discontinuity between the staple and the bore.
The two pieces of rolled copper are sprung together, heated in a soft gas flame and a small amount of solder flowed in to hold them. The trick is to keep the amount of solder "small", i.e., put on what looks like an inadequate amount and trust that it will flow all the way to the end of the seam.
The straight part of the staple tube is a snuggish fit inside the bore of the shawm. I "glued" the tube into the body of the staple with some thick shellac, which took rather longer to set than I had expected. If I use this staple design again, I would use straight rosin or pitch or even hot-melt glue to fasten the tube.
The next step is tuning the shawms, to be told in the next post.
Friday, March 5, 2010
More Shawms - reaming and turning
When I show these shawms to people, one question many ask is how the internal tapered hole was made. I tell them that I push in a tapered steel bar and turn it by hand round and round and round until it is done. This often leads to a short blank silence as though I am being deliberately obtuse, but here is my proof.
I used the same two sizes of reamers from the first shawm making. Here is the larger one with a handle clamped on. As I mentioned the first time around, the handle allows a lot more control and torque to be applied.
And here it is in action, getting on toward the end of reaming. When the reaming is complete, virtually the whole length of the reamer will have entered the hole, so there is still some work to do.
This thicker reamer is easier to use since it is stiffer and does not flex much. The thinner reamer used to shape the narrow end of the bore tends to twist if I force it too much. This time, I did the wide end shaping first, and then put in the narrow reamer on the end of an extension (sorry, no photos for this).
Here's the extended smaller reamer, and you can see the twist on the working part. I just straighten it out in the vice and carry on - more carefully, for a while.
The essence of all this is that it is all pretty low tech. The reamer material is just mild steel; no hardening is necessary. I have honed the big one once, but the narrow one is still on its original sharpen from when I made it.
This particular shawn had the curved bore, and it was obvious from turning the narrow reamer that something unusual was happening inside. In the best of worlds, there should be a seamless transition between the part reamed by the wide reamer and the narrow reamed part. Because of the curved bore, this one had a bit of a step. Again, nothing much to be done about it, but carry on and hope.
Looking down the throat with the reaming complete. I used several grades of rasp to extend the bell's flare down the throat to produce a smooth transition.
You can see that it is a bit off-centre from the curved bore, and not quite circular, since getting an even rotation was a little difficult.
After the reaming, the composite body workpiece went back on the lathe.
Here is a view looking into the bell, showing a circular packing piece held in place by friction with the inside of the bell, as a transition between the driven centre (not quite visible on the nut in the foreground). This simple arrangement worked remarkably well and did not slip significantly while I was doing the finishing turning.
Here is the workpiece with final depth cuts made all along the body. This was actually quite an exciting part of the work, since the transition from a roughly shaped piece to a slinky, silky smooth result all happened in the space of less than an hour. All of a sudden, the chrysalis was transformed into a butterfly.
The "butterfly" stands on the right here with the original shawm in the centre, and with the workpiece for the second shawm on the left, which has been bored but no more.
To bore the second body, I just clamped it on the bench, put the long 6mm auger in an electric drill and just bored it by sighting along the length. Whether by luck or skill, this produced a much straighter and centred bore than the first one. Reaming was straightforward, and I was able to get a pretty good smooth taper all the way along the bore.
Here is the second shawm glued up and back on the lathe, well advanced in final turning.
Just 30 minutes later, it looked like this.
I have to say, at this point, I was pretty well pleased with the look and feel of these. So, here are a couple more gratuitous images of the turned bodies.
You can see some filler on the right hand one, dressing a spot where I had cut a little too vigorously during the rough shaping.
Since the timber was recovered building framing, there are several nail holes in both pieces, so there are actually spots of wood filler all over both of them. No-one has noticed or commented on this at all.
A worm's eye view of the first shawm, showing the internal shaping of the bell.
Next stage: doing the staples and reeds at the other end. Not so easy!
This thicker reamer is easier to use since it is stiffer and does not flex much. The thinner reamer used to shape the narrow end of the bore tends to twist if I force it too much. This time, I did the wide end shaping first, and then put in the narrow reamer on the end of an extension (sorry, no photos for this).
The essence of all this is that it is all pretty low tech. The reamer material is just mild steel; no hardening is necessary. I have honed the big one once, but the narrow one is still on its original sharpen from when I made it.
This particular shawn had the curved bore, and it was obvious from turning the narrow reamer that something unusual was happening inside. In the best of worlds, there should be a seamless transition between the part reamed by the wide reamer and the narrow reamed part. Because of the curved bore, this one had a bit of a step. Again, nothing much to be done about it, but carry on and hope.
You can see that it is a bit off-centre from the curved bore, and not quite circular, since getting an even rotation was a little difficult.
Here is a view looking into the bell, showing a circular packing piece held in place by friction with the inside of the bell, as a transition between the driven centre (not quite visible on the nut in the foreground). This simple arrangement worked remarkably well and did not slip significantly while I was doing the finishing turning.
To bore the second body, I just clamped it on the bench, put the long 6mm auger in an electric drill and just bored it by sighting along the length. Whether by luck or skill, this produced a much straighter and centred bore than the first one. Reaming was straightforward, and I was able to get a pretty good smooth taper all the way along the bore.
You can see some filler on the right hand one, dressing a spot where I had cut a little too vigorously during the rough shaping.
Since the timber was recovered building framing, there are several nail holes in both pieces, so there are actually spots of wood filler all over both of them. No-one has noticed or commented on this at all.
Next stage: doing the staples and reeds at the other end. Not so easy!
Thursday, March 4, 2010
More Shawms - long boring
Since I was making these shawms to be joined up as a single unit, the body pieces of wood were longer than in the first one, which had a midsection joint (see this old post). The lathe bed was long enough, but I wanted to make some improvements to the long 6mm drill.
I had made a drill for lengthwise boring the first shawm by extending a 300mm auger with some steel rod.
This is the joint formed with some copper shim wrapped around the rod and soldered together. It was strong enough, but required an oversized hole to enter the bore, which defeated quite a bit of the point of being able to make long bores.
This new joint was made by lapping the shafts for about 15mm and brazing them together (reclaimed my gas plant, ha ha), giving a substantially uniform joint (after grinding off the high spots).
Here is the blank for one of the shawms, mounted in the lathe with the hollow centre. The bed is long enough, but not too long. Notice that the drill guide and the workpiece are not far apart, and this probably contributed to the drilling problem to be described.
With my son Francis working the lathe's treadle again, I lead the drill into the end. The boring started well enough, and the first 300mm was easy enough. After that, things went a bit sour, with the drill seeming to present lots of friction and the shaft getting very warm. I greased it with some candle wax, which made a bit of difference, but by no means not a complete solution.
Also, the drill became more difficult to withdraw to clean out dust, which rather suggested that there was a curve or kink in the bore, somehow.
Since parts of the bore needed opening up anyway, I ran in a 10mm reamer to widen the hole. This reduced the drag on the 6mm rod for a while, but there was still this feeling of a curve or kink. The bore should have been 560mm in length, but I gave up at about 450mm.
At this point, I wasn't sure that the workpiece was actually going to be usable, or how off-centre the bore had become. I took a length of 3mm brazing rod, filed a flat on the end, and used it in an electric drill to extend the bore all the way through. As you can see in the picture, the brazing rod has come through well off centre, but not so much to be unusable, so I carried on.
I finished the boring with an electric drill and some brute force. Sighting through the bore, there was a definite curve, deviating nearly 6mm from true. Acoustically, I guessed/hoped that this would be tolerable, but the reaming would be interesting.
Jumping ahead, here is the body and the bell being joined. The body piece has been shaved down approximately with sideaxe and drawknife, centred on the eventual path of the bore. I turned a tenon in the wide end to mate with a 30mm socket drilled in the end of the bell with a spade bit.
I tried holding these pieces together in a furniture cramp for gluing, but could not get the two pieces to sit squarely together reliably. I could have made some supporting blocks or something, but this arrangement in the photo was easier to do, mostly. It has the clamping force applied centrally, via the nylon cord running down through the bore to the weight. The force is only about 3kg-wt, but it was enough.
I used a modern polyurethane glue (Gorilla Glue), which is plenty strong enough, with some space filling ability as well.
Let's leave it alone to set and come back in the morning...
This is the joint formed with some copper shim wrapped around the rod and soldered together. It was strong enough, but required an oversized hole to enter the bore, which defeated quite a bit of the point of being able to make long bores.
With my son Francis working the lathe's treadle again, I lead the drill into the end. The boring started well enough, and the first 300mm was easy enough. After that, things went a bit sour, with the drill seeming to present lots of friction and the shaft getting very warm. I greased it with some candle wax, which made a bit of difference, but by no means not a complete solution.
Also, the drill became more difficult to withdraw to clean out dust, which rather suggested that there was a curve or kink in the bore, somehow.
Since parts of the bore needed opening up anyway, I ran in a 10mm reamer to widen the hole. This reduced the drag on the 6mm rod for a while, but there was still this feeling of a curve or kink. The bore should have been 560mm in length, but I gave up at about 450mm.
I finished the boring with an electric drill and some brute force. Sighting through the bore, there was a definite curve, deviating nearly 6mm from true. Acoustically, I guessed/hoped that this would be tolerable, but the reaming would be interesting.
I tried holding these pieces together in a furniture cramp for gluing, but could not get the two pieces to sit squarely together reliably. I could have made some supporting blocks or something, but this arrangement in the photo was easier to do, mostly. It has the clamping force applied centrally, via the nylon cord running down through the bore to the weight. The force is only about 3kg-wt, but it was enough.
I used a modern polyurethane glue (Gorilla Glue), which is plenty strong enough, with some space filling ability as well.
Let's leave it alone to set and come back in the morning...
Wednesday, February 10, 2010
More shawms - a brace of them
About the middle of 2009, I had the first shawm to a working state that was good enough to make me consider making some more. I wanted to see what level of improvement I could achieve, based on my experience with the first one.
Differences I planned were:
Easy parts first
Doing the bells would be a simple start, while I thought out the detail of the other end.
Here is a 4" x 4" composite slab being prepared. It has been centre bored already, hence the groove for the hollow centre visible here. The G clamp and steel angle is a basic rest for the end turning of the bell, and has been improved on since this photo was taken.
Taking the bell profile from the original image from Trevor Robinson's book (see this earlier post), I made saw cuts through the block to about the right depths, and snapped and chiselled off the waste wood.
This photo shows the right end still in a relatively raw state, but the left end has some more accurate depth grooves turned in it, and I have done some rounding down.
Some time later, here are the bells, still siamesed, but with all the external roughing out done (but still oversize, since I hadn't decided the detail of the main body). I have shaped most of the inside of one end, as much as was worth doing by end turning. Note that I have replaced the G clamp and steel angle with a more elaborate (and more robust) crosswise tool rest for end turning.
Once I had taken the internal shaping close to a final finish, I snapped off the internal nubbin (wot the fixed centre is poking into) and sawed the bells apart so the other one could be turned around and hollowed out.
Then there was a distraction, in the form of a commission which meant that nothing happened with the shawms for about four months (I will talk about this distraction in a later post because it is interesting in itself).
Differences I planned were:
- do it in one piece, which is a more period style
- focus rather more on the detail of the staple and reed end of the instrument, and less so on the bell end, since this is more critical to the final performance.
- make two at the same time, to see what consistency could be had.
Easy parts first
Doing the bells would be a simple start, while I thought out the detail of the other end.
Taking the bell profile from the original image from Trevor Robinson's book (see this earlier post), I made saw cuts through the block to about the right depths, and snapped and chiselled off the waste wood.
Once I had taken the internal shaping close to a final finish, I snapped off the internal nubbin (wot the fixed centre is poking into) and sawed the bells apart so the other one could be turned around and hollowed out.
Then there was a distraction, in the form of a commission which meant that nothing happened with the shawms for about four months (I will talk about this distraction in a later post because it is interesting in itself).
Saturday, January 23, 2010
Lathes - Towers and Things
There was no real reason for these other than practice, so I put them aside when done. By good luck as much as anything else, these turned out well, even though the heartwood runs through all of them. Over a year later, I made these bobbins into part of the staples of two new shawms which I will write about later.
About this time, the local (SCA) Baron and Baroness made a call for donations of largesse for use as gifts to visitors, etc to the Barony. I had nothing in hand to offer, but it triggered an idea.
These were made from more old rimu stock left over from house building. The platters are rather smaller than the bowls mentioned in an earlier post, and turning did not offer any major problems.
More Towers
The tower thing has some significance in the local SCA group, so I saw scope for some more work here. Having done turning mostly with well seasoned wood, I turned to using some green wood.
I knew that shrinkage during drying was going to be a problem, so I bored out the centres to remove the heartwood and perhaps give some space to shrink into.
So, although these turnings were ruined, it was a good learning experience.
As I found, this is not a great wood for turning. It has softer and denser regions, and the grain tears quite easily, making it hard to get a particularly fine finish. Since these towers would be painted, I was not too worried about this. The photo shows plenty of filler to smooth over the nasty bits.
Once these were painted a garish canary yellow with decorative highlights in black, they were presented to the local Baron and Baroness on their accession during Canterbury Fair in 2009.
Here they are in action, as it were.
This pretty much ran out that particular tower phase, but it may come back again. From here, in late 2008, I went on to start making my first shawm, which has been described in the first set of posts to this blog.
Friday, January 22, 2010
Lathe - Early Turnings
For some reason, I started off using my HP lathe by turning bowls on the lathe. In retrospect, the only reason for doing it was that we needed some basic wooden bowls, and at the time, it seemed like a simple enough thing to do. These photos all date from March-May 2008.
I used some old rimu timber left over from building our house in 1990. Being from 200mm planks, these bowls were about 200mm diameter, which was right at the edge of what the lathe is capable of handling. Even with the new 6:1 gearing, the work would stall at the slightest overload from the chisel.
By dint of having very sharp tools, and making only fine cuts, progress was possible, but rather slow, even with most of the waste wood in the centre chopped out with a chisel.
The bowl that really went quite well was from a piece of fairly green birch wood. The wood was softer and this turned out well enough and mostly held its shape as the bowl seasoned. It was good enough to give away to a friend as a present.
When I came to repeat the turning with the other half of the split birch log some six months later, this had become rather too hard to easily turn and had developed enough of a split to be a problem. I decided early on that this was not going to work well and binned it.
So, no more bowls on the agenda at the moment. Until I do something about a lower ratio on the drive pulley, it's just not worth it.
So, no more bowls on the agenda at the moment. Until I do something about a lower ratio on the drive pulley, it's just not worth it.
Wednesday, January 20, 2010
HP Lathe - using it
I'm using conventional modern lathe tools - just a basic set until I get a feel for what works well for this style.
It is not the same as a powered lathe, and particular techniques are different. The available power at the spindle is no more than 100W, and the useful speed range is 400-600 rpm. Deep or heavy cuts are not possible; fine cuts are the order of the day. The low power sets limits to the practical size (diameter) of work.
Tools need to be very sharp, especially for seasoned wood. Making sawdust is inefficient except for fine finishing - making long shavings is much better. Someday, I want to try hook or ring chisels as an alternative to “ordinary” turning chisels. A hook chisel has a loop bent in the end and a bevel ground on the inside of the loop – a bit of a trick to make (see www.robin-wood.co.uk/turnframe.htm). A ring chisel could be easier to make - a short length of steel tube brazed on the end of a shaft mounted in a handle and put a bevel on the inside of one end of the tube for the cutting edge.
There are other techniques to be learned as well: how to operate the treadle for extended periods without falling over, and while keeping the tool steady .
I have been changing the spindle pulley to find a good drive ratio. I found that I didn't need a groove for the drive belt in the flywheel; it sits there without any trouble, as long as the pulley is in the right place.
The original spindle pulley shown here was 50mm diameter, hence giving a drive ratio of 12:1 speed up off the flywheel. This didn't give much torque, meaning lots of belt slippage and stalls - very annoying.
My current pulley is 100mm diameter, hence only 6:1 speed up. The lower spindle speed does not seem to be a big problem, but more torque is good. Now I can easily turn material to 100mm diameter, and can handle 200mm diameter work with some care.
As well changing the pulley size, I can tinker with the travel of the treadle. The initial travel of the crank arm was about 100mm. Increasing this to 150mm travel along with the larger pulley makes for a better feel.
Future plans
Rebuild the bearings on the crank arm for better lubrication and sealing against dirt. The 8mm bolt which is the bearing shaft on the treadle is wearing out rather faster than I expected, although not so fast now that it is mostly in my relatively clean workshop.
Change the drive belt from nylon cord to a more authentic leather belt. This is not so old fashioned as you might think. During my apprenticeship, I have used commercial milling machines dating from well into the 20th Century which had leather drive belts, and which worked quite well. This will probably need a tensioning idler wheel to the drive belt, which should allow better tension control and less belt slippage.
Make another driven centre for the headstock. The first one is a bit inconvenient to fit material onto, sometimes, and the points are not as sharp as they could be.
Make a hollow centre for the tailstock. I will need this for long length-wise drilling of the bores of musical wind instruments. (as you may have noticed from the earlier posts about shawm making, this has already happened).
Do more work with green wood, i.e., fairly unseasoned wood.
Is it a good lathe? Well, sort of, within its inherent limitations.
What would I do differently if I made another one? Make the flywheel heavier by using more layers of lamination. Take more care with the spindle trueness.
Is it fun to use? Oh yes! It's more approachable than a power lathe, because it doesn't spin fast, and it's pretty quiet, and because all the action is at a human scale. And it keeps you warm in a cold winter workshop.
It is not the same as a powered lathe, and particular techniques are different. The available power at the spindle is no more than 100W, and the useful speed range is 400-600 rpm. Deep or heavy cuts are not possible; fine cuts are the order of the day. The low power sets limits to the practical size (diameter) of work.
Tools need to be very sharp, especially for seasoned wood. Making sawdust is inefficient except for fine finishing - making long shavings is much better. Someday, I want to try hook or ring chisels as an alternative to “ordinary” turning chisels. A hook chisel has a loop bent in the end and a bevel ground on the inside of the loop – a bit of a trick to make (see www.robin-wood.co.uk/turnframe.htm). A ring chisel could be easier to make - a short length of steel tube brazed on the end of a shaft mounted in a handle and put a bevel on the inside of one end of the tube for the cutting edge.
There are other techniques to be learned as well: how to operate the treadle for extended periods without falling over, and while keeping the tool steady .
I have been changing the spindle pulley to find a good drive ratio. I found that I didn't need a groove for the drive belt in the flywheel; it sits there without any trouble, as long as the pulley is in the right place.
As well changing the pulley size, I can tinker with the travel of the treadle. The initial travel of the crank arm was about 100mm. Increasing this to 150mm travel along with the larger pulley makes for a better feel.
Future plans
Rebuild the bearings on the crank arm for better lubrication and sealing against dirt. The 8mm bolt which is the bearing shaft on the treadle is wearing out rather faster than I expected, although not so fast now that it is mostly in my relatively clean workshop.
Change the drive belt from nylon cord to a more authentic leather belt. This is not so old fashioned as you might think. During my apprenticeship, I have used commercial milling machines dating from well into the 20th Century which had leather drive belts, and which worked quite well. This will probably need a tensioning idler wheel to the drive belt, which should allow better tension control and less belt slippage.
Make another driven centre for the headstock. The first one is a bit inconvenient to fit material onto, sometimes, and the points are not as sharp as they could be.
Make a hollow centre for the tailstock. I will need this for long length-wise drilling of the bores of musical wind instruments. (as you may have noticed from the earlier posts about shawm making, this has already happened).
Do more work with green wood, i.e., fairly unseasoned wood.
Is it a good lathe? Well, sort of, within its inherent limitations.
What would I do differently if I made another one? Make the flywheel heavier by using more layers of lamination. Take more care with the spindle trueness.
Is it fun to use? Oh yes! It's more approachable than a power lathe, because it doesn't spin fast, and it's pretty quiet, and because all the action is at a human scale. And it keeps you warm in a cold winter workshop.
HP Lathe - construction
I needed fairly dense stable timber for the major structural items. I used recycled rimu framing timber – well seasoned, stable, reasonably hard, cheaper than new wood. I cut all the timber and cut the tenons and mortices by hand, but I cheated and dressed the large items with my planer, which also made it easier getting the beams nice and square. I drilled large holes with brace and bit, but used a battery drill for small holes (there were not actually very many of these).
The spindle is made from a 16mm steel bolt running in sealed ball bearings. In period, this would probably have been forged nearly to shape and dressed with a file to final size. The bearings might have been brass or bronze sleeves, or more likely a hard wood such as lignum vitae, greased with tallow. These would have been lossy bearings.
The threaded end of the bolt allows different headstocks to be mounted and unmounted quickly, but is not any sort of period method that I am aware of. Morse tapers are distinctly too modern and too hard to make. A friend Bruce helped me by turning the spindle down on his metalworking lathe, fined down to a firm but not tight fit in the ball races. I tinned the shaft with solder where bearings would be and drifted them into place.
The flywheel shaft is a 12mm bolt also running in ball bearings for convenience. The bearings are inset into the wooden structure and are not very obvious to a casual glance. The flywheel and shaft assembly can be readily removed from the frame for transport or storage. The mounting bush for the flywheel was also turned on Bruce's lathe, and I arc-welded a fastening flange on. My smithing skill is not up to forge welding.
The flywheel consists of three layers of plywood glued together. Plywood was convenient to use and is conceptually sympathetic with period construction in that a period flywheel would have been made by laminating several layers of planks. Smaller planks are more available than large flat sheet, and cross plying improves the strength and stiffness of the flywheel. I took some pains to balance the flywheel, but because of its slow speed, the balance does not need to be particularly good.
I had some doubts about using wood screws to fasten the metal cover plates. However, I found a reference to drawings of screws in a late 15th C manuscript, showing detail of them being used to fasten plates in a matchlock mechanism, so that was OK (see “One Good Turn”, by Witold Rybczynnski – this is a good read; recommended). However, machine screws were not in period use, so I did not use grub screws to attach bushes to shafts - these were locked in place with tapered pins through the shaft.
The threaded end of the spindle was not wonderfully true. I could have gone back and made another spindle being more selective about the parent bolt, or cut threads into a trued shaft, but I was running out of time. My workaround has been to make the driving centres with a compensating offset, noting the position where these run true and locking them in place with a locknut. It's workable enough .
I fastened the beams of the bed to the three uprights with coach bolts. In period, bolts might have been used, although the particular types of bolt would have been different (square head, not hex). However, bolts would have been expensive, and fastening would most likely have been with trenails (wooden pegs or dowels) or snug fitting mortice and tenon joints. I chose to use bolts since this allowed the lathe to be collapsed for storage or transport. All other major joints were inset and mostly dowelled, and fastened with modern adhesives.
The moveable poppet locks in place on the rails with a wedge through it as shown here.
The leather strap through the wedge is a labour saving device to prevent the wedge from popping out onto the floor when tapped on the narrow to free it (which happens often enough to be a nuisance).
I was aiming to show the lathe at a mediaeval fair in early February 2008. My original timeline had some spare time in January for me to get some practice in using it. However, the reality was that I was adding finishing parts and adjusting the running gear right up to the last week, and had virtually no time for practice. So I did my practice during my demonstrations at the fair. No-one seemed to mind - there was lots of interest from many people, and a small queue of other woodworkers keen to have a go. To see some images, go to sg.sca.org.nz/gallery/main.php?g2_itemId=3007, then find your way to page 9 of this album.
The spindle is made from a 16mm steel bolt running in sealed ball bearings. In period, this would probably have been forged nearly to shape and dressed with a file to final size. The bearings might have been brass or bronze sleeves, or more likely a hard wood such as lignum vitae, greased with tallow. These would have been lossy bearings.
The threaded end of the bolt allows different headstocks to be mounted and unmounted quickly, but is not any sort of period method that I am aware of. Morse tapers are distinctly too modern and too hard to make. A friend Bruce helped me by turning the spindle down on his metalworking lathe, fined down to a firm but not tight fit in the ball races. I tinned the shaft with solder where bearings would be and drifted them into place.
The flywheel consists of three layers of plywood glued together. Plywood was convenient to use and is conceptually sympathetic with period construction in that a period flywheel would have been made by laminating several layers of planks. Smaller planks are more available than large flat sheet, and cross plying improves the strength and stiffness of the flywheel. I took some pains to balance the flywheel, but because of its slow speed, the balance does not need to be particularly good.
I fastened the beams of the bed to the three uprights with coach bolts. In period, bolts might have been used, although the particular types of bolt would have been different (square head, not hex). However, bolts would have been expensive, and fastening would most likely have been with trenails (wooden pegs or dowels) or snug fitting mortice and tenon joints. I chose to use bolts since this allowed the lathe to be collapsed for storage or transport. All other major joints were inset and mostly dowelled, and fastened with modern adhesives.
The leather strap through the wedge is a labour saving device to prevent the wedge from popping out onto the floor when tapped on the narrow to free it (which happens often enough to be a nuisance).
I was aiming to show the lathe at a mediaeval fair in early February 2008. My original timeline had some spare time in January for me to get some practice in using it. However, the reality was that I was adding finishing parts and adjusting the running gear right up to the last week, and had virtually no time for practice. So I did my practice during my demonstrations at the fair. No-one seemed to mind - there was lots of interest from many people, and a small queue of other woodworkers keen to have a go. To see some images, go to sg.sca.org.nz/gallery/main.php?g2_itemId=3007, then find your way to page 9 of this album.
Subscribe to:
Posts (Atom)