1) Hollow punches, which you could make if you don't already have;
2) Sandwich the copper between sheets of something more sturdy that you can then machine more "normally", or just laminate it onto a sturdy substrate (think 'printed circuit board', where they routinely drill and rout very thin copper that is glued to a fiberglass substrate).
Shim punch and die set, not sure where you will get one nowadays ,but I used them all the time for making shims for machinery alignment work. I have seen sets on Ebay. Unfortunately this set does not have a 9/16" punch but you get the idea and could make one from ground flat stock and some drill rod for the size your after.Harden and temper both when fishished machining . The idea of the clear plastic top guide is so you can see to align the holes for making concentric washers.
Here is the link to a set so you can see what I'm on about.
|65%3A1|39%3A1|240%3A1318|301%3A0|293%3A3|294%3A50 Disclaimer I have no association with this seller apart from the fact that I have purchased item from him previuosly and am happy dealing with him.
Well, in my case "working on" means "making a new cylinder, piston, rod and head for fun". The originals may fit, but where's the fun in that?
Besides -- I just called those folks about parts for a .15; they said "no can do". They just bought out Estes's stock of Cox parts for 1/2 a million $$, there's reported to be an astonishing amount of oddball stuff in there, but either they don't have it inventoried yet or the stuff really isn't there.
Hmmm---Glue the copper to a flat surface. I would probably use a piece of Aluminum flatbar, just because I have a lot of small pieces. Little superglue on one surface, make a sandwich and clamp.
Do it in the mill as a vertical trepanning operation. I would use a boring head. Grind a very sharp bit and cut the ID of several. Change to an outside bit and do the OD. Should leave a very crisp edge with no burr.
No -- we're talking shim stock thicknesses here -- 5, 10 mils at most.
The purpose is to adjust the compression of the motor to the particular fuel and propeller used. Since I'm hacking the cylinder and piston out of the solid it's especially important -- I have every faith that I'll get it wrong the first time.
Jim Wilk> > You can't just turn and part them from an annealed brass
mils at most.
and piston out
faith that I'll
I'm on Jim's side on this one. Parting off would give you good control over the thickness even though it may be somewhat wasteful due to the thickness of the parting tool wasting stock. If the coupound is not accurate enough then mount a DTI to set the next cut point. How thin a piece can you cut this way? Try it and find out, you might be surprised . phil
"Cox" no longer exists. Estes owned the brand but didn't do anything with it but sell ever less well made and harder to find .049s. They recently sold a whole warehouse full of stuff to a distributor, although it's not clear whether they sold the Cox name to go with it.
Besides, I'm making the cylinder, head, rod and piston as a training exercise. So it may not have _exactly_ the same dimensions as the original. (It may not run, either -- I just noticed tonight that I had a pretty serious boo-boo in the port timing. I'm going to finish it off and give it a whirl; I plan on cheering if the engine can turn under it's own power. Then I start working on the next one with an eye to all the lessons I've learned on this one).
I ground the back end of my parting tool thin for jobs like this. The end needs to be angled very slightly to cut off the work without a burr, but not enough that the cutting force deflects it sideways. Test it by shaving less than the tool's width off the end of a rod and checking if the cut is flat.