Machinist question

My thought is it would be gummy and heat from friction would cause it it to fail as a bearing. Wood brgs were soaked in oil and certain type of wood. Anything can be machined if not a liquid, some materials are tougher

jaybmiller wrote: A lot depends upon the speed of the shaft or whatever is in the bushing. Low speed = not much heat...UHMW plastic would be better, or a bronze bushing in the plastic... One of those gotta know th eapplication first to decide what's the best material....

steve(ill) wrote: Deck boards are some type of pine or fir... very soft .... not good bearing material

composite

Thad in AR. wrote: thendrix wrote: If you're going to machine plastic use sharp HSS tools. If you get a lot of tool marks take a honing stone and just take the keen edge off. RPM high or low? Thanks I was guessing carbide.

Relatively low, you don't want unnecessary heat at the cut. If you can sharpen a carbide bit really sharp, you'd be OK. A carbide insert is not sharp enough to work well. It will work, but not great. You can really put a sharp edge on HSS.

My father in law wanted some bushings made for some kind of old implement he had and we made them out of hedge. He said it worked and we did that a lot of years ago and haven't heard anything since. I know he still uses it cause he don't get rid of anything.

Thad in AR. wrote: Tbone95 wrote: Thad in AR. wrote: thendrix wrote: If you're going to machine plastic use sharp HSS tools. If you get a lot of tool marks take a honing stone and just take the keen edge off. RPM high or low? Thanks I was guessing carbide. Relatively low, you don't want unnecessary heat at the cut. If you can sharpen a carbide bit really sharp, you'd be OK. A carbide insert is not sharp enough to work well. It will work, but not great. You can really put a sharp edge on HSS. Thank you. I’m taking notes. I’m in the learning stages of HSS sharpening.

Since you're talking notes, carbide tools, especially interested tools, have a less keen edge than HHS tools do. I've been told this is because carbide doesn't shear like HHS does, it's more of a beating action. The rounded edges on inserted carbide tools will do more "pushing" soft materials than actually cutting them. If this material is UHMW and you're milling it I would say with a 2 or 3 flute 1/2" HHS end mill on a manual mill you could run in the 1500 RPM range and be ok. A smaller end mil run a little faster and a little slower for a bigger end mill. Adjust your feed and speed according to your desired finish and what how it feels. When I used to cut plastics I used aluminum vice jaws with sharp or almost sharp dovetails cut in them. I found with straight jaws you kinda get a push upwards on the part from gripping on the corner. The dovetail grips above the corner and tends to hold better. Also with plastics, if you put a piece in a vice and tighten it then go to lunch, when you come back tighten the vice just a little. Like said before UHMW is basically a milk jug and it will form to pressure if left for a while. The good grip you had before lunch can turn into a loose projectile after lunch

fixer1958 wrote: My father in law wanted some bushings made for some kind of old implement he had and we made them out of hedge. He said it worked and we did that a lot of years ago and haven't heard anything since. I know he still uses it cause he don't get rid of anything.

 I thought about hedge when I made a BEARING FOR MY OLD DISC. It's so dense, it might not soak up enough oil or grease to keep it lubricated. With a low speed and little use, it wouldn't have really mattered, but I grabbed what was close and easiest to get at and the mulberry has lasted for 4 years now. Just pump a couple pumps of grease in it every once in awhile.