The Offcial Machinist Thread: Revised 01/04/2014

[ramses]

10 bucks will cover it, just include a prepaid shipping lable inside the box with the cylinder. I'll PM you my address, ship it to me when your ready.

Don't forget the housing

[clemsonguy1125]

Has anyone here had experience turning solid rubber. I was thinking for a small bore piston hybrid it could make a decent piston.

[jackssmirkingrevenge]

I thing you're better off sharpening a tube in order to serve as a rubber cutter.

[clemsonguy1125]

I did that in my pen gun, but it wasnt airtight and it would be a pain to cut a 1 inch thick piston thats going to go in a 1/2 piston housing.

[LeMaudit]

A custom cutter would certainly work the best, but maybe not for a significant length.
Never done that but my first guess would be to freeze it first. It seem that's the usual way. Google gives some precious clues, here's the first one:

Need Help!- Turning Rubber??? How to?

[clemsonguy1125]

Thanks, do you think Im better of just having one machined from aluminum, the issue with that is the smallest bolt I can find to hold down the sealing face is bigger than what it is sealing against. Im afraid that if I sanded down the bolt, the face would detach itself from the piston.

[LeMaudit]

What do you mean you can't find a small bolt?
If you go to a hardware store like Home Depot, you'll find easily small bolts.

Maybe I don't understand. Care for a drawing about what you have in mind?

[clemsonguy1125]

Well I want the barrel is going to be 1/8 inch pipe, the smallest bolt and washer combo I can find to hold the sealing face to the piston is larger than the port it is sealing against. I guess Ill just bump up the tee to 3/4 and the face its sealing against to 3/8.

[Technician1002]

I cut a rubber piston seal out of a sheet of rubber with a hole saw, then "Turned" it down on the drill press. It won't cut properly with any cutting tools but I did find that it abrades down nicely using a course cut bastard file.
As you can see in the photo, the rubber has a rough edge from the hole saw on the sheet of rubber. The piston has a smooth edge after it was sanded down on the drill press with a file.

[LeMaudit]

May I suggest you look again?
This is from Home Depot (or another similar hardware store I don't remember).

And you can find much smaller bolts in hobby stores.

[clemsonguy1125]

Ill check home depot, last time I looked at lowes it was for a slightly smaller barrel size. Ill check at the hobby store as well.

[LeMaudit]

At the hobby store, in particular if they do RC cars / planes, you'll find really really small ones!
At least with diameter 2 times smaller than my picture. I have some... can't find them in my mess

[jackssmirkingrevenge]

Never done that but my first guess would be to freeze it first. It seem that's the usual way.

Oh thank you. Now you got me wondering how to "borrow" liquid nitrogen from work!

[Gippeto]

Machine the piston from virgin teflon...incorporate a parachute seal into the face or o-ring the thing. Piece of cake.

No need for a bolt on sealing face.

If teflon won't cut it (barrel cuts into the piston) use nylon. Very commonly found as a sealing material in oilfield regulators.

[clemsonguy1125]

I may have one machined from aluminum, with a oring like you suggested. Ill sketch one up. Ive just got to figure out how to use sketch up, Ive never really bothered with it before.