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View Full Version : What Type of O Ring to Drive Watchmakers Lathe



polepenhollow
03-20-2013, 12:02 AM
I wanted to put on a new "O" ring to drive my Peerless watchmakers Lathe. What type of "O" ring material would anyone recommend using. Soft Buna, Neoprene, Polyurethane ? There are quite a few different types available. Suggestions appreciated.

J Tiers
03-20-2013, 12:22 AM
You might do better with one of the drive belt cords that you cut to length and melt the ends together..... No need to disassemble then.

I got a length from either Stock Drive Parts, or Small Parts Inc. As Small Parts Inc has gone T/U as part of Amazon.com, they don't seem to stock it, but I think McMaster has it still.

I used a 1/8" or so size (in mm) on the Boley, which works quite well.

darryl
03-20-2013, 12:25 AM
I think the ones you can heat/melt together are urethane. Have not tried them, but supposedly they work well.

Arthur.Marks
03-20-2013, 12:59 AM
I see you're in my vicinity. FWIW, I have two belts left over from something for which they ended up being unsuitable. ⌀6 and ⌀8mm round urethane, McMaster 8112K33 and 8112K34, respectively. I joined each at about 30" length, but if you could use one I'll just shorten + join it to whatever you need. ⌀8mm might be a bit too big for a watchmaker lathe? I dunno.

dian
03-20-2013, 08:03 AM
you are supposed to use some kind of glue, when you melt them together. does anybody know, what glue that is?

Doozer
03-20-2013, 08:16 AM
For urathane you just light both ends on fire and then push them together.
This will put out the flame and while the ends are still molten, square them
up as best you can before it solidifies.

--Doozer

mars-red
03-20-2013, 09:46 AM
Maybe some of the types you splice are different but the type I use is the green "swiss" belting with that funky texture. It grips like crazy and requires no glue - as stated, you just melt the ends and keep them pushed together until cool, then trim with a razor. I have used large o-rings too and they do also work well - I used ones I had on hand already and I don't know what kind they are. They were a dark charcoal gray color, if that helps.

Rustybolt
03-20-2013, 12:38 PM
On orange Eagle brand belting you just melt it and stick it together. Hold it for a good three minutes or until it's cool.

dian
03-20-2013, 04:33 PM
well, at the place i get the stuff, they say tey use glue, but the will not disclose what kind.

but the original question is interesting. an o-ring i have from the manufacturer of a machine sure feels different that the nbr or even viton ones you can get. and i notice these get pretty hot fast.

Rustybolt
03-20-2013, 04:38 PM
Maybe some of the types you splice are different but the type I use is the green "swiss" belting with that funky texture. It grips like crazy and requires no glue - as stated, you just melt the ends and keep them pushed together until cool, then trim with a razor. I have used large o-rings too and they do also work well - I used ones I had on hand already and I don't know what kind they are. They were a dark charcoal gray color, if that helps.

Is this the stuff that's real hard to pull apart once its cooled?

mars-red
03-20-2013, 06:24 PM
Is this the stuff that's real hard to pull apart once its cooled?

I would expect any of them should be real hard to pull apart but I've only ever used the green stuff... but in answer to your question yes the spliced area seems as strong as the rest of the belt (I haven't tried pulling on it until it breaks though).

Arthur.Marks
03-20-2013, 06:26 PM
The green urethane belts hold, to my understanding, full strength once joined. The standard manufacturer procedure is to hold the ends against a flat, knife tip solder gun for a specified number of seconds based on diameter. The watchmaker books alternately explain using a pocket knife held above an alcohol burner. Hold for the required time, withdraw the heated knife, and compress the aligned ends for another specified amount of time based on diameter. It isn't very long -- on the order of maybe five minutes or so off the top of my head. Then they are recommended to wait up to a half hour or so before "full strength" is assured. In other words, just make sure it has completely, fully cooled before putting under any significant tension. The "flash" is trimmed even with the belt profile. Voilą!

Now, every watchmaking book I've ever seen says it can be done without a jig to align the belts and a simple pocket knife + bunsen burner. I guess I don't join belts enough to align them as good as they do :) So I have done it before with a scrap piece of aluminum and a milled channel to accept the belt ends. Works good enough.

A hobbyists' source for the green urethane belts I'm talking about as well as the leather variety. Never used the leather variety, so I can't comment. http://www.watchtoolsonline.com/Lathe-Belting_c19.htm

Rustybolt
03-20-2013, 10:28 PM
OK. This is the stuff we're using for drive belts. .125 belting material streatched out to make a belt .063.
Good stuff.

J Tiers
03-21-2013, 01:30 AM
Yes, mine is the green with a matte finish. I melt the ends in a flame and press together, aligned in the corner of a piece of angle.... or free-hand.

You can't let it burn much, it gets spongy.... you just melt it and press together. a good joint then has a pressed-out ring of melted stuff all around, which you trim off with a knife, or can grind smooth. It is as strong as any other part of the belt.

I don't see what a glue could do to be better.....

Evan
03-21-2013, 03:52 AM
I use ordinary neoprene O-rings on my D200 Unimat. Neoprene O-rings are available in two durometers. The harder ones will run at higher rpms without slinging off the pulleys but are more critical as to correct size. This matters a lot on my Unimat because I converted it to a 1/2 hp DC motor with a speed controller. O-rings can transmit a surprising amount of power and run very smoothly.

Don't try silicone O-rings. They do not hold up to repeated flexing. Viton is good I have heard but much more expensive.

darryl
03-21-2013, 04:37 AM
The last belt I had on my Unimat was an O-ring. I went so far as to grind the edges of it to make it a V belt. It has never failed, and I may use it again when I get further along on my update of that lathe.

brian Rupnow
03-21-2013, 09:01 AM
A standard Buna N rubber o-ring will do. To join the ends of cut o-rings use cyanoacrylate (crazy) glue.