5 Ways of driving things in the lathe
We've talked a lot about our folding treadle lathe. But let's not lose sight of the attachments, which also deserve our focus.
When using a lathe, the work is driven by the headstock and supported, if necessary, by the tailstock. Bowls and similar pieces can be gripped or screwed on to the headstock and wouldn't need tailstock support. A long spindle can be held multiple of ways, but it is driven by the headstock, and the tailstock simply functions to support it.
Old turning manuals show a million ways of holding the work. If you look at 19th century and pre-19th century depictions of lathe tools and attachments, you'll see a lot of effort devoted to driving the work. The reason is very simple: Turners of that era did not have our wonderfully made three- and four-jaw universal chucks. They also didn't have standard interchangeable tapers and threads.
Modern wood lathes all have hollow spindles, so some-sort-of center tasked with holding the work will be able to be popped into the spindle. Some very inexpensive lathes use a set screw and a collar to hold the center, but better (but still inexpensive) lathes have a tapered hole in the spindle, which can hold a center by friction. The standard American woodturning lathe will have an MT2 (Morse Taper 2) hole in the spindle for a center driver, and a threaded outside, 1"- 8 TPI, for screwing on larger chucks and face plates. Larger lathes will have all larger tapers and threads. All standard accessories with MT2 shafts and 1"-8 threads are interchangeable. This includes the lathe accessories we sell. All similarly tapered and threaded accessories from other vendors will fit our Gramercy Tools treadle lathe as well.
Long, thin work is typically held between headstock and tailstock centers. Bowls and other short workpieces are typically held in a chuck in the tailstock. But all sorts of work-holding arrangements arise depending on the situation.
The tailstock is simply there to support the work and keep a long piece steady while you turn. The headstock center is what actually drives the work. Whatever way you are holding the work, the headstock center has to force the work to turn and not slip when cutting force is applied.
Four Prong Drive Chuck
Historically, the most popular way of driving spindle work is by using what's known as a "four prong center" or a "four prong chuck." (see photo above). You'll see these centers in old turning literature, but other options are eclipsing them. The four prong center is very simple to use. You drill a small hole in the center of the the piece and then put two saw cuts at 90° around that. Some people will just put in the center hole and then use a hammer to bang in the prongs. Then it goes in the headstock. The prongs in the slots drive the work. To make it work, you'll need to make saw slots or bang in the prongs, and I don't like either method. So we supply a crown center with our lathes, which we think is a lot easier to use.
Crown chucks
A crown center (above) looks like a crown, hence the name. The center pin of a crown center is spring-loaded. To mount your work, just put a center mark on the work at the center; put the loaded pin on the mark; and then tighten up the tailstock. With the tailstock tightened, the crown edge digs in. That’s it - you’re done. If you manage to do something silly and accidentally jam a tool, such that you would stop the work from spinning - and this is especially true on an electric lathe, as treadle lathes really don’t have the power - a traditional four prong center will just keep on moving. This can cause real damage to the work, split the wood, break a tool, etc. With a crown center, on the other hand, the work is held more gently by crown points that do not penetrate the the workpiece that deeply. Because the individual crown points are not stuck that deeply, a jammed tool causes less havoc. The crown points just slip and work a groove in the work. Not ideal, but not a big deal. The turner just notes the problem, tightens up the tailstock again to engage the crown points again, and then resumes working.
We stock two sizes of crown driver; a 1 inch crown, which comes with a lathe, and a smaller half inch crown. I like them both. The only real downside that I can see for a crown drive is when your workpiece's diameter is very, very small diameter work and even a 1/2" crown driver will be too big.
Faceplate
While it is rarely used today, a traditional way of holding the work is using a faceplate. The work is attached to the faceplate - typically with screws, but also sometimes with little clamps - and away you go. There is no built-in centering mechanism, so it's not surprising that nowadays the faceplate is the workholder of last resort. I’ve personally never used one, but it was a very common traditional way of mounting.
A screw chuck (left) and a Four Jaw Universal Chuck
Here we have the most common way of holding a bowl for turning. You start by drilling a hole in the center of what will become the hollow side of the bowl blank and screw the stock onto a screw chuck (above left). The screw chuck can be driven a bunch of ways. In this version, the disk at the bottom of the chuck is clamped in a four jaw universal chuck. With the work in the lathe the outside of the bowl is turned, and in this particular case I also turned a recess in the base. With the outside done, I then flipped the blank around and clamped the work by expanding the four jaw universal chuck (above, right) into the recess I cut in the base. This method works solidly and reliably and is probable the most common way of clamping a bowl.
On wood lathes, four jaw chucks like the one above are standard. The jaws move as a group so the work is centered. Independent four jaw chucks are used mostly on metal lathes when the work is not round, or needs very careful manual centering, more accurately than a universal lathe can provide.
The four jaw chuck for a wood lathe comes in all sorts of permutations. We stock a nice but fairly primitive one without the attachments. The price ranges from "not a lot" to several hundred dollars, depending on features, precision and capacity. The jaws come in various sizes and are usually interchangeable on a particular chuck. Depending on which jaws are used, you can clamp on the inside of a recess by expanding outward, or on a lip clamping inward. The lips of the chuck jaws are tapered so grab the work solidly even if the recess or ledge on the work is pretty small.
On a final note, here are some pictures of some of a couple of chucks from Bergeron's 1742 "Manuel Du Tourneur." We see the elements of a faceplate and screw chuck - and even a very early independent four jaw chuck from a time when cutting screw threads was a big deal. But figure 8 is both interesting and practical. Particularly for production work, the turner would make a collet by drilling a piece of wood the same size as the stock; then cut slots in it thereby creating fingers; and then use a ring to force the fingers tightly closed. Or course this would only work for one size of stock, but for that size it works fast and tight. These types of collet chucks were very popular especially in production work.
I am barely scratching the surface of the different type of chucks that were used, but for most of us, a crown center coupled with some sort of four jaw chuck will cover 95% of the work we’re going to do. If you find yourself do oddball stuff, that’s when you start doing some research especially in old books.
I'll talk about the tailstock when I next write about centers.
Various chucks from Bergeron's Manuel Du Tourneur Paris 1742 - #8 - collet chuck. #9 - Faceplate chuck with screws. #10 what looks like a very early four jaw independent chuck
Disc support for holding handles for drilling - Bergeron's Manuel Du Tourneur Paris 1742
Joel's Blog
Built-It Blog
Video Roundup
Classes & Events
Work Magazine