I need to make some head shims/gaskets for a Cox .09 that I'm working on. These need to be of thin copper or brass, round, with an OD of about
9/16" and an ID of about 1/2".Any suggestions on cutting them out evenly so that they're neither burred nor bent when I'm done?
Thin stock, use scissors. Use copper, brass would be too hard.
Four options come immediately to mind:
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).
3) Water jet4) Laser
p.
Water jet and laser are beyond the capabilities of my shop, but the hollow punches or backing it up with sacrificial material both sound like viable options.
The punches will leave burrs, I suspect, but if they're even enough I can beat them flat between flat plates.
No idea on your sizes, but I've been able to use a hand paper punch that makes single holes for a 3 ring binder that doesn't bur, bend, or mutilate copper or brass.
Coat thin copper with resist. Scribe outline of gasket with fine point. dump in ferric chloride.
Kevin Gallimore
Ever consider making them from copper wire? Wrap the wire around a form, make one cut to turn the coil into rings then solder the ends to make rings
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.
On a different track than most of the answers, I think I would use a dremmil tool. Just drill the holes undersize and then use grinder stones to bring them up to ,marked size.
LLB
You mean these?
Ebay:
370204317171 These are for the .049, but this guy claims to have more parts than anyone else.Pete Stanaitis
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Tim Wescott wrote:
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.
Heat, cold, or a razor blade to remove.
Have you tried here? $4 for 3 gaskets.
You can't just turn and part them from an annealed brass water pipe nipple?
jsw
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.
.09 that I'm
brass, round, with
Jim Wilk> > You can't just turn and part them from an annealed brass
water pipe
mils at most.
the particular
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
That seems doable. Buy a stack of brass shims - sheets of brass.
Then select a hole punch of 1/2" and 9/16. These are used on paper, plastic, leather and the like. The trick will be a firm enough backing that allows a punch and won't distort.
You can make these - mount them in a drill press and press downward...
Grind pipe or tubing and harden if possible - maybe using an additive.
Or buy them from Cox for your eng> I need to make some head shims/gaskets for a Cox .09 that I'm working
"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.
jsw
I second that idea--toner transfer and photoetch printed circuit methods work for laying the resist pattern. Good for making batches of parts.
Cut your shim stock in 1" squares. Cut more than you'll need in a lifetime. The more the better.
Stack them up and sandwich them between
2 pieces of AL about 1/8" thick. Clamp well, drill through the center then bore to the ID.Turn an arbor for your lathe that will just fit inside the ID. Drill and tap a hole in the center of the arbor. Make some sort of end cap that will hold the gaskets and AL snugly on the arbor.
Chuck the arbor in your lathe and turn the whole mess down to the OD.
It won't take as long as it looks. I've done the whole thing in about 1/2 hour.
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