View Full Version : cutting holes in Buna fabric piston cups

08-02-2003, 11:51 PM
I have an old Clark Yardlift without model number or other identification. It has a 6 cylinder Continental engine and 8' mast. The tilt cylinder piston cups are leather and worn out. The cups are 4 1/2" o.d., 7/8" cup height, 1/4" thick with a 2 1/8" hole in the center of the cup with 6 bolt hole pattern. How can these holes be placed in Buna fabric replacement cups? thanks Paul

08-03-2003, 01:49 AM
You should be able to use a hollow punch to make the hold in the buna fabric. They are used to make holes in gasket material and are available at most tool and supply houses.

You didn't say what size the holes are but if they don't have a punch the size you need you can made on by turning down a rod or tubing to the size you need and sharpening the end. I have made several from stainless steel tubing.


08-04-2003, 11:27 PM
Thanks Joe for your response. The center hole is 2 1/8" and there are 6 x3/8" holes in a 3" pattern. The rod end of the cylinder is held on by 16x1/2" bolts. If I could find a model number I might be able to get the cups already cut. I was thinking of using a fly cutter but I think your suggestion would be better. Paul

08-05-2003, 12:39 AM
You can get a 4 1/2" OD by 5/8" high Buna-N cup from McMaster-Carr (9411K33). It has a 2 1/2" ID but you could make a metal spacer to get it down to 2 1/8".

I've had good results drilling fabric-reinforced rubber with Brad-point wood-boring bits.


George Hodge
08-05-2003, 10:24 PM
You might try sandwiching it between two pieces of hardwood and drilling it with a sharp metal cutting bit.Of course it would need to be clamped together.

Forrest Addy
08-06-2003, 12:05 AM
Forget the cups and modify the old piston make a new one that takes standard disegrin (sp?) cylinder seals.

Talk to a hydraulics outfit.

08-06-2003, 01:09 AM
I previously used a pair of scissors. Maybe a pair of shears (big scissors) would work for the 1/4 in thk. I also used a scalpel (razzor blade) if you are only cutting a few.

Increased quantity would justify tooling