Lathe video on YouTube

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.

Lathes - Towers and Things

Having decided that bowls were not ideal, I looked at some easier (smaller) work.

These kumihimo bobbins were made from green cherry wood, which was part of some prunings from my prunus sakura tree in July 2008.  They are about 40mm in diameter and about as long (~1.5").

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.

The result is shown here in the form of a pair of candle holders, being a tower on an island surrounded by a moat.

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.

 I don't have a photo of the finished holders, showing the gilded towers on the green island surrounded by the blue water, but you can get some of the effect from the photo here, during painting.  In the "water" in the moat was some glitter paint which I initially intended as wavelets, but realised were actually reflections of the stars above.  I realised that I had recreated the content of "Long May She Stand", which is the Baronial anthem song. This made a nice narrative to accompany these presents when they were eventually given to the Baron and Baroness of Ildhafn when they stepped down a couple of years ago.

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.

Here are a couple more towers as candlesticks, turned from a freshly pruned cherry branch.  The original branch was about 100mm (4") in diameter.

The turning went so smoothly, like peeling an apple.  And the finish was only about as smooth as a peeled apple.  The wood was too soft to put any finer finish on, so I put them aside to dry and harden.

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.

All for nought. A week later, things had changed as you can see.  The localised shrinkage was more than the wood could bear, and "Crack!".

So, although these turnings were ruined, it was a good learning experience.

I went back to some old wood for the next set of towers.  These were designed as decorative finials to set on top of the Baronial pavilion.  They are about 300mm high and 100mm across the base.  The wood is a locally grown oregon, with quite a pink tint, that is not very obvious in this photo.

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.

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.

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 20^th 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.

HP Lathe - background and design

This is based on an article I wrote for a local human-powered vehicle newsletter (Kiwi HPV).  It's not about any sort of vehicle but it does involve human power. It's about a human-powered wood lathe that I built in 2008.

I had been sort of interested in a wood lathe for some years, but I did not have any specific need, and it was not a burning desire, so nothing had happened. However, I started thinking about making woodwind instruments, which really does require a lathe.  Even so, I was still pretty lukewarm about having another large piece of power machinery in my workshop, taking up space.

Then I was persuaded to make a lathe that didn't have this problem, and one that connected with my interest in early tools and techniques.

Some history
Lathes are old machines. They predate Roman times. I read of person's one categorisation of early lathes into ones that you sit down to use and ones that you stand up to use. The “sit down” type were usually bow lathes where the shaft is directly driven by a bow-string pushed back and forward by the apprentice or other source of cheap labour. The “stand up” type were generally pole lathes where the shaft was directly driven by a cord pulled down by the operator's foot and pulled up by a springy pole acting as a return spring.

The form of a lathe has been well established for many centuries. There is a drawing in the “Mediaeval Housebook” (c.1475) of a screw cutting lathe with all the basic forms: horizontal bed with two rails, and two movable vertical supports for the work.

One of Leonardo da Vinci's notebooks from about 1505 shows a sketch of a lathe with a large flywheel driven directly by a treadle and crank. The shaft speed would have been very slow, and the ~2 meter diameter flywheel would have presented some practical difficulties in stopping and starting quickly. The key aspect of this lathe is that has continuous rotation rather than the alternating forward and backward action of a bow or pole lathe. This makes it useful for more detailed engineering work, turning or swaging or polishing of small metal items, especially if the shaft speed can be increased. Using a belt drive from a treadle-driven or cranked flywheel to a smaller spindle pulley is a way to do this.

Designs
There are plenty of designs around for basic powered wood lathes. Woodworking magazines through to at least the 1960s regularly ran articles on DIY lathes. If you go looking on the web, you can probably find copies of these.

I came across a web-published book by Steve Schmeck on how to build a treadle lathe (www.manytracks.com/publish.htm) (he also does recumbents; surprise!).  “That doesn't look so difficult”, I thought. However, there were a couple of details in the structure I was not so keen on.
Then I came across Roy Underhill's book “The Woodwright's Shop”, where he describes a smallish treadle powered lathe still in current use in his workshop. This had a structure that looked stiffer than Steve Schmeck's design, and I liked it a lot. As well as the look, the material cost was not not very much, so if it turned out to be a dud, I would not have invested much.

I used the dimensions from Steve Schmeck's design, and incorporated the triangulated supports for the flywheel from Roy Underhill's example.

So, my lathe consists of a triangular subframe supporting the flywheel and spindle. The subframe is supported on the left end of a footplate which also mounts the righthand support for the bed. The bed is two horizontal beams fastened to front and rear of the three uprights. A moveable upright supporting the tail stock sits on the beams of the bed and can be clamped in place with a wedge. In principle, this structure should be collapsable for transport or storage.

My intent with this lathe was not particularly to produce an historically accurate example of a lathe from the 16^th Century or earlier. I wanted something that captures the much of the "feel" and appearance from that time, and could be shown off at mediaeval re-enactment events, but was also practical and useful in the here and now for doing real work. I also wanted to be able to make it using hand tools as much as possible.

What I have ended with is a representation of a style of lathe that could have been extant in the 16^th Century but certainly was in use in the 17th Century. At the same time it has some modern components that are not too obtrusive.