Also, many thanks to Chucker as I would not have even tried this without reading his post.
Ordered a 1lb box of scrap leather form ebay. Was advertised as 4-5 oz. It measured out to 1.5 - 1.75 mm. The cup I have from OCP is 1.4 mm so pretty close.
I cut down the 3/4" copper cap with a tubing cutter.
Cut out the leather to ~1.25" in diameter and soaked in water for ~ 15 minutes.
Pressed the leather into the cup with a 1/2" piece of copper.
Let it dry overnight then trim off the excess with a razor blade.
Punched a 1/4 inch hole in the middle.
Did not have any neatsfoot oil so used some Obenaufs leather oil.
Installed on my 288 and is working well.
I bought some boots from the goodwill for the leather.
Duane, you can do this with the pump tube of whatever GPA you need a cup for, then they are just right size.
hikerduane wrote: I guess a socket or similar size would press the leather for inner diameter.
Or a ss bolt up the center, a couple washers and hex nut to form them in the copper cap. I let them dry overnight since I soak mine in water. Yes, the center hole needs to be punched out before doing this.
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it works better if you soak in a mixture of metho and water ., alcohol and water
much better punching the hole after forming the cup
light weight mineral oil works very well , even just normal engine oil .