treadle lathe

Roger Davis is a fortune teller, and a fellow Hoosier.

Roger and I met quite awhile back over on the Sawmill Creek forums talking about, what else, old tools. Not long after I published the last entry, Roger advised that the walnut crank probably wouldn’t last long. Now, it hasn’t actually failed but it didn’t take long for a bit of wobble to develop. Roger is a fellow woodworking enthusiast who also has day-job metal working skills and the equipment for prototyping aerospace instrumentation. Roger offered to make a “bulletproof” steel crank and I took him up on the offer. I’m absolutely amazed that he offered and acted so quickly. The crank is here and already in use. THANK YOU Roger!

By the way, for the spalted maple fans, be aware that there’s such a thing as spalted steel. This crank has a bit of spalting which I consider early onset patina.

The Treadle Mechanism

When I was much younger and more interested in high performance automobiles, one of the things I learned about was “unsprung weight.” That’s the weight of the car in the wheels, axles and undercarriage that isn’t moderated by the suspension system. A lot of unsprung weight dampens a car’s performance. The lower the amount of unsprung weight, the better performance can be tuned. This lathe takes that approach with the treadle. I’ve seen a lot of treadle lathes that have huge heavy treadle mechanisms. It seems to me that the effort that goes into operating a heavy treadle has the same dampening effect as excessive unsprung weight in cars. I can appreciate how a heavy flywheel adds momentum, but not if it has to drag along the dead weight of a heavy treadle. The lighter treadle was part of what drew me to this design.

Three lightweight parts comprise the moving components, the treadle itself, a Pittman link, and a spacer bar that keeps the treadle parallel to the center line of the lathe. All three are of oak approximately 3/4″ by 1-1/2″ in measure. The treadle pivots on a 1/2″ diameter pin that’s held in the walnut block on the foot of the right leg. The pivot hole itself is 3/4″ diameter providing enough play for easy operation. The driving end of the pedal holds another 1/2″ diameter pin that engages the Pittman link. The bottom hole on the Pittman link is also 3/4″ diameter, allowing for a lot of angular movement. At the top of the Pittman link is a slot that is “a whisker” larger than 1/2″ wide, enough to ride freely on the crank’s 1/2″ diameter drive pin. Two u-shaped oak blocks anchor the spacer bar. The anchor pins are 1/4″ bolts fitted in 1/4″ holes in the blocks. The pivot holes in the spacer bar are 5/16″. Thinking these parts might need lots of wiggle room, I tried a much loser version and ended up with a lot of clunking. The tighter version runs smoothly and without any binding.

As before: Il meccanismo è molto scorrevole!

First Turning – a 24 inch object

A couple of posts back, I mentioned that the flywheel was cut round using a jig on the band saw. Well, that “round” was approximate. It wanted some truing, not a lot but enough to make me wonder about how well a belt would track. How to get it trued up? Makeshift time!

Finding a “tool rest” of an appropriate height was the first challenge. What the photo shows is an alternate use for the pair of saw benches I made ages ago. Flop them over on their sides and stack them “just so,” and the result is something good for supporting a newly arrived round nosed scraper. Not having a readily available treadling apprentice, I parked a chair beside the upturned saw benches, sat down, and treadled while leaning over and holding the chisel.

The wheel is now round. The drive belt won’t have to put up with a roller coaster ride. If you watch the wheel turn, you’ll see some side-to-side wobble, for which there are two responses: don’t watch, and it’s not enough to affect operation. 🙂

More spinning things! There are lots of little step-by-step things since the last time. Summarized, two axles are now running on ball bearings and held in an assembly of two legs. Simple.

The left leg holds two bearing blocks. Both are set in only as deep as they need be. The flywheel axle and the headstock spindle do not run completely through the left leg. There’s a single bearing for the flywheel axle.

The headstock spindle has two bearings. Leftmost is a thrust bearing which absorbs lateral pressure on the spindle. Immediately next to it is a ball bearing for the radial load.

The flywheel axle is 1/2″ steel rod, common stuff from the home center. The headstock spindle is also common 5/8″ steel rod. I used that size because it is the same as a ShopSmith spindle and several parts are available for that size spindle (see the post 2 previous to this for actual part numbers).

The right leg, of course, has through holes for both the flywheel axle and the headstock spindle. The bearing for the flywheel axle is on the inside / left face of this leg, making both flywheel bearings close to the wheel itself. The headstock spindle bearing is on the outside / right face of the leg.

The legs are bolted together with 3 carriage bolts, each running thorough a spacer block, two through the feet and the third just below the rails. It’s solid!

Last, there’s a crank piece made of walnut. Remember, the blacksmith moved away, and I don’t have enough metal working skills to bend cranks in 1/2″ steel rod. So, I used a block of walnut, and pinned it to the flywheel axle and the crank stub with pins made from 8-penny nails.

And… yes, that’s a pile of sandpaper (YIKES!) in one of those photos. Hate the stuff. But the wood needed it.

Result: Il meccanismo è molto scorrevole! (http://translate.google.com/#it|en| is your friend)

In yesteryear they called it a “puppet.” Today, we call it a tailstock. Same purpose, different names.

Earlier I mentioned that I’m aiming for a more modern interpretation. It is in jest that I forgo the old world costumes, and in practicality that I seek a smooth running contrivance.

a short digression … There was a time that I imagined having the “village blacksmith” fashion some parts for this lathe. A strange thing happened on the way to see the smith. I discovered he left long ago. The quaint little village I live in is intentionally quaint. I came here over 30 years ago as a convenient place to live while I pursued employment in the corporate, private, free-enterprise world. I didn’t move here because it is a quaint little village. Yet, about that time a town council was elected with the purpose of keeping the place little and quaint. There is no development here. No new people arrive (or are welcome) to help share a constantly increasing tax burden. Long story short, the smithie was one of the first to recognize the peril of perpetually increasing taxes and he left. Word has it he’s in Cody Wyoming where there’s plenty of smithing to be done and people who actually appreciate industrious private enterprise.

So, “here ya go, Shannon.” Shannon asked in a comment to a previous post about my intentions for the spinning parts. Let’s do the tailstock/puppet first. Many replicas of old time lathes want to use a large screw with a sharpened point as the tail center. I wanted a bit less drag and smoke! Live centers all seem to be attached to tapered fixtures. How would I support one of those? Some time ago, “TrialAndError” briefly mentioned using a “morse taper socket” in the lathe he built. It wasn’t until a week or so ago that I searched for such a thing on eBay and discovered they really exist.

The morse taper socket I bought is simply a 1″ diameter chunk of stainless steel machined with a #2 morse taper hole, and then hardened. It is 4 inches long and includes a closed slot machined crosswise near one end. I assume this slot is used in applications where the socket moves within a quill.  Beware when buying this piece.

You can find them in the $30-$50 range on eBay, or for $9.70 at Amazon. Shop around.

Drilling the 1″ hole through my puppet was a task best done on a saw bench. It is low enough to allow the right ergonomics of a very long auger in a hand brace. The short swing of the hand brace made for slow boring, but also made it easy to check constantly for accuracy.

The result is a very tight fit, requiring a block of wood and rubber faced mallet to drive the socket into the puppet. If, I find it moves under turning pressure, I’ll add a pin through that slot.

UPDATE: After using this for a couple of years, there was no movement of the socket. A pin through that slot isn’t needed at all. However, I did modify the socket by drilling a 1/4″ hole through the closed end. I can insert a bolt in that hole to knock the tapered center out. It’s a good practice to knock that center out and not leave it in the socket when not in use. (DAHIKT)