Holding and boring HDPE, and/or LDPE as a bushing

[Buckshot]

.........First what I'm doing is to have a 1/2" dia steel rod fit inside the bored plastic sleeve, which itself fit's inside a steel cylinder. The 1/2" rod will only make a low speed 90* rotation back and forth to open and close a passage.

I purchased a 1"x12" solid rod of each material. The plastic sleeve will be about 2 to 2.5" long. I need to bore and have an almost .0000" fit. Or more likely a slight interferance fit. I'm counting on the natural lubricity of the plastic to allow the smaller steel rod to rotate.

I'm thinking that the best way to bore the hole in the plastic would be to press it into the outer steel sleeve, chuck the assemby and then bore?

What kind of SFM should I use, and feed for boring this type plastic.

Thanks,
Rick

[Evan]

What temperature range is this to operate in? HDPE has around eight to ten times the linear coefficient of expansion with temperature as steel. Even a slight change in temperature (friction?) will cause a significant change in dimension. For that tight tolerance it isn't going to work.

[This message has been edited by Evan (edited 12-05-2004).]

[Don Clement]

I would suggest using Turcite for the bushing. Turcite is acetal plastic Delrin and machines easily. See http://www.boedeker.com/turcax_p.htm

Don Clement
Running Springs, California

[wierdscience]

For LDPE OR HDPE as fas as you can spin it and RAZOR sharp tools.
You can run your feed rate .020" per rev or better for roughing cuts and then drop to .005" for the finish pass.

I use a tool(HSS)with a 1/16-3/32" radius on the tip and honed sharp first with an oil stone and finished off with a buffing wheel for the best results.

Yes the two do have exspansion problems,but depending on what the application is and the surface conditon of the pin you shouldn't have any problems with the setup sticking even if the hole is .001" undersized.