Machining polyurethane?

[MrHorsepower]

I need to machine some polyurethane. I don't know what the grade is. It's the stuff that hi-po bushings for cars is made of. Does anyone know how to do this. What kind of cutter should I use? I used to work at a place where they turn large rubber rollers down using a wire wheel on a tool post grinder. Any thoughts?-Dave

[Turbo2Pete]

Hrm... as far as machining, I don't know... but you can get liquid urethane from Grainger, in several durometer ratings, we've used it for making motor mounts... it might be easier for you to machine a mold & cast the part you need.

Pete

[Karl_T]

How hard it is makes a huge difference. Anything over 80 shore A machines quite nicely with HSS tooling finely sharpened. Use lots of positve rake and lots of relief. Example, for boring use an old endmill. Grind all but one flute off.

It also sands very nicely.

The lower durometers can be cooled/frozen for better machining.

Karl

[granto]

I'll second what Karl T said. I machine 90 Shore A (which I've used for suspension bushings) with HSS tooling.

We cast any parts lower than 90 durometer.

[kheri]

I am also intersted about this liquid urethane. Could you provide me the website of Grainger ? Thanks Pete

[Turbo2Pete]

http://www.grainger.com/Grainger/sea...Urethane&xi=xi

I think this is 80A I know they used to carry a few durometer ratings... I supposed you can check with locktite for others

Pete

[CWBAILEY]

Almost any plastic is machinable. The general rule is the softer the material the smaller the cutting edge angle. So larger rake and clearance angles and reduced approach angle.

The greatest problem is the tensile strength of the material as it does not chip like harder materials and will wrap itself around the tool and the work causing heat and welding. The best approach is to mill the work rather than turn it this produces short chips and avoids the stringing problem.

The speed should be about 120 Metres a minuite but should be adjusted to suit if overheating occurs.

Finish cuts should be repeated as push off will occur and if the component is oversize resist the temptation to increase the cut but run the finish cycle again.

Have fun

[MrHorsepower]

Very interesting. When casting, do you need to pressurize or vacume? Can anyone recomend some good reading, online or otherwise?-Thanks