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View Full Version : Is there away to to turn rubber ?



David S Newman
10-19-2007, 03:19 PM
I need to replace the friction drives in an old hand held tachometer, these are T shaped , ie two different diameters so can't be punched out. The instrument is an Elliot of London and probably 30 years old so replacements not available. Has anyone out there any ideas on how to turn rubber ? I will cut a piece off an old tyre for the material. David

wirewrkr
10-19-2007, 03:25 PM
Rather than attempting to turn rubber, check out a supplier of lab equipment, as they used odd shaped rubber bits for beakers and such.
I have an old SW static tach that I'm goiing to need rubbers for as well, that is the first place to look.
Robert

flyby
10-19-2007, 03:30 PM
Easiest way...freeze the rubber, then grind to shape with a dremmel tool...
GOOD LUCK with your venture!
Bert

thistle
10-19-2007, 03:53 PM
razor blade , die grinder, router with super sharp hss cutter......

ahidley
10-19-2007, 03:59 PM
make a mold on the lathe and melt and pour in the rubber. Or use RTV or some of the repair epoxys for automotive plastics . This stuff is sold at automotive paint supply companies. there also is rubber used by tire repair companies to repair tires, mostly on heavy equiptment. I bet that they would fill a mold for you

SherpaDoug
10-19-2007, 04:00 PM
Here is a second vote for freezing. I have turned polyurethane potting that way.

RKW
10-19-2007, 04:37 PM
Devcon makes some urethane products that might help you here. You can use additives that can make it more flexible if necessary.

http://www.devcon.com/devconcatsolution.cfm?catid=14

RKW
10-19-2007, 04:40 PM
Speaking of rubber ...

Does anyone have any experience with various adhesives that work with bonding rubber to aluminum or steel? In my experience most just allow the rubber to be peeled off even after fully curing.

motomoron
10-19-2007, 04:47 PM
Rubber grinds well, generally. Cyanoacrylate adhesives, particularly the rubber fortified ones stick to rubber like a crazed octopus.

ammcoman2
10-19-2007, 06:39 PM
Try a hockey puck - tough as H*** and very easy to turn with a sharp cutter. I have made replacement tips for hiking sticks and will use it to replace the tip on my very old Starrett tachometer when I get a "roundtuit".

Cheers,

Geoff

Norman Atkinson
10-19-2007, 06:44 PM
The Armstrong Cork Company turned rubber rollers for the spinning and weaving industries by grinding.

Mcostello
10-19-2007, 08:32 PM
I've used HSS tools as sharp as can be honed, fairly good results. Never tried hockey pucks. If you use"preutilized" equiptment for parts, rubber can easily come from old room A/C units. Neatest idea I've heard on the 'net was to use piece of hacksaw blade heated and bent to a "u" shape thusly directing chip down into pan.

JRouche
10-19-2007, 09:29 PM
I had to turn some bushings for a car. I froze the rubber (poly) solid in the freezer for the night. I sawed the pieces to length with a sawzall and a tree trimming blade.

I chucked the cuttoffs up and turned them with carbide inserts. I turn everything with inserts. They turned down to within a thou.

I also had to drill out center holes, not as critical so no boring after drilling.

After they thawed I was curious about dimension changes but the poly didnt change. JRouche

BobWarfield
10-19-2007, 11:23 PM
I second the vote for hockey pucks. Bought a box of 50 off eBay for like $8. They machine pretty nicely and are useful for all kind of things.

Best,

BW

Thomas Staubo
10-20-2007, 07:19 AM
Freezing the rubber seems like a good idea, but might perhaps not work well on all types of rubber.
Another old age method, maybe most suited to softer rubber, is described by L.H. Sparey in his book "The amateur's lathe" from 1948. This method relies on 'slicing' the rubber with home-made tools, take a look at the attached scanned image below.

http://img151.imageshack.us/img151/9215/rubberturningzx1.th.jpg (http://img151.imageshack.us/my.php?image=rubberturningzx1.jpg)

Allan Waterfall
10-20-2007, 09:34 AM
Speaking of rubber ...

Does anyone have any experience with various adhesives that work with bonding rubber to aluminum or steel? In my experience most just allow the rubber to be peeled off even after fully curing.

Loctite 480.

Allan

Alistair Hosie
10-20-2007, 02:45 PM
warning trying to melt rubber gives off tremendous clouds of smoke and toxic fumes be careful buddy !!Alistair

gellfex
10-20-2007, 03:21 PM
maybe I just don't get it, but why does it need to be so fancy? Isn' this for contact with a turning shaft? My ancient Starrett handheld tach has a steel sleeve with a 1/8" thick hard rubber disk on the end of it that has a beveled borehole that look like it was made by a tiny lathe centerbore.

If the point is to use the outside diameter of the end, just turn a piece of delrin with a slot in it to snap in a rubber O ring. That way you can turn a 1:1 nosepiece for any diameter shaft where you can't get at the end.

Alistair Hosie
10-20-2007, 04:12 PM
gellfex is correct this can be done without rubber ,nylon or similar material will work just as well Alistair

darryl
10-20-2007, 04:19 PM
Another vote for hockey pucks as a source of rubber. I cut them on a table saw with a sharp blade. You can make a decent hole in it with a piece of tubing sharpened at one end and used in a drill press. Use some dish soap for lube and don't go too fast. Once you have a hole, it can be set up on a stub in a lathe and ground to shape. A dremel mounted on the crosslide will work. A toolpost grinder will work better. Grinding does make a big mess.

Old printers often have rubber rolls of various sizes in them. That sometimes works out for me.

Sounds like you need two accurate diameters- you'll probably have to grind to get that done properly. It might help if you can mount the rubber to a metal tube first. The tube would be made to fit the shaft first, then the rubber mounted, then the grinding.

Allan Waterfall
10-20-2007, 05:04 PM
Last time I turned and bored a hocky puck,a positive insert worked a lot better than HSS.From my limited experience,the HSS tended to make rubber bands and the positive insert didn't.

Allan

Norman Atkinson
10-20-2007, 05:26 PM
Deleted
No one listening to someone who has actually seen it done- in a professional shop.

David S Newman
10-21-2007, 04:07 PM
Thanks for all your replies and advice. I made the friction pads today using the Sparey method described in his book and mentioned by a member in this thread , and it worked very well and quickly, suprising what a couple of sharp tubes and a mounted razor blade will do in the lathe. Mr Sparey was a very inventive man. David

Thomas Staubo
10-21-2007, 09:41 PM
I am glad that it worked out okay, for you, David.

PS. I was listening to you, Norm.;) You said something about the rubber was removed by grinding, IIRC.