Watchmakers Lathe - Shaft locking pin

So I finally broke the belt on my watchmakers lathe. I've never had to replace it before and taking apart the head-stock was a new process for me.

On the far end of the head stock is a brass colored knob that screws the collet. It mechanically activates the shaft by engaging a crescent shaped pin in the shaft that fits into a slot cut in the hole of the brass knob.

Anyone know where I might be able to get one of these pins? I don't have much in the way of tooling to make a new one.

I've also never been able to positively ID the lathe. I suspect it may be a Boley lathe due to whaat little I know of its provenance but I've never seen one like this. The triangular way is unusual to me.

They might be too wide but have you considered the link-belt type belts you can assemble and disassemble?

https://www.amazon.com/Jason-Industrial-3L-LINK-5-Accu-Link-Adjustable/dp/B00A9ZNCJM

Here's one in 3/8".

If you take the collet closer completely out, will the other end some out of the head stock?

The crescent shaped pin you refer to is called a Woodruff Key. They are a common standard machine part available in many sizes from many vendors. Measure yours and look them up on the net.

You can buy lengths of solid poly belting in round, V, and flat shapes and different sizes. You cut the stock belting and weld the cut ends together with heat. It is a simple process that eliminates the need to disassemble the head stock spindle.

Quade said:

If you take the collet closer completely out, will the other end some out of the head stock?

Click to expand...

Yes, you have to remove the collet closer completely and then remove the belt hub to get to it.

aninventor said:

The crescent shaped pin you refer to is called a Woodruff Key. They are a common standard machine part available in many sizes from many vendors. Measure yours and look them up on the net.

Click to expand...

Thanks! One piece of knowledge closer to knowing something about engineering. Where do people acquire all this knowledge ? After praying on the garage floor for a bit I think I'll just order up a replacement.

Quade said:

They might be too wide but have you considered the link-belt type belts you can assemble and disassemble?

Click to expand...

aninventor said:

You can buy lengths of solid poly belting in round, V, and flat shapes and different sizes.

Click to expand...

I'll have to give a different style of belt a shot. Thank you both for the suggestions.

I can only say the lathe is European and I have no idea who made it. I got my first watch lathe in 1958 and have had plenty of time to decide that the best design is the American Webster Whitcomb, dating to around 1870. Even German makers, including Leinen and G. Boley, produced exact copies because most American watch repairers knew not to buy the European style lathes. Levin and Derbyshire were still making WW lathes in the late 20th century. I think most of the old European style lathes in America were probably brought over by immigrating watch repairers who only knew the lathes they had learned on.

Anyway, belts don't care what lathe they are on, and 3/16" round leather belts fit almost any watch lathe. I used it for years and tried various traditional ways of splicing it. Rubber O-rings never lasted very long before breaking. But decades ago polyurethane belting became the preferred way to drive watch lathes. Most watch lathes use a 5 mm round section belt. There is an American maker, but I had to buy 200 feet of yellow or clear Rounthane belting at a time to get it and I have found it becomes brittle and worthless after a while. For years, I have been buying the rough surface green PU belting in 10 meter lengths from Chinese sellers on eBay. I find it easy to weld and have not had any turn brittle yet.

It is a pain to take a headstock apart to install an endless belt, particularly if it is a modern ball bearing lathe like a Levin or Derbyshire. Welding a new belt while wrapped around the lathe pulley is the way to go. Old plain bearing lathes are easier to get apart and cleaning the bearings occasionally is not a bad thing.

Here is one belt source: Green Rough Surface PU Polyurethane Round Belt for Drive Transmission Machine | eBay

Larry