Copper washers, fairly tightly dimensioned, 25 to make:-
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I'm thinking the best way to get them finished to size and with a good finish will be by making a punch & die, but is it feasible for the small/home shop to do the whole thing that way, maybe first punching a blank out of plate & then shaping as a second operation? I don't fancy my chances of doing the whole thing as a turning job & getting a satisfactory finish.
Any suggestions, from those who 'know' or just fancy a guess, welcomed.
That has set me thinking about forming them on a mandrel with the OD left free, for finishing in the lathe. Saves trying to get the exact volume of material for forming.
Anything other than copper, I'd be doing something along those lines....
I think Id go with a punch and an oversized outer collar. Start with a blank thats got to much material, but is slightly to small in dia if you see what I mean, then use a punch pair to form the inside to the chamfer and dia by cold flow. The outer ring prevents it splitting out, and forces the flow. Then a mandrel to clean and size the outer. From the drawing I cant see a tolerance on the inner dia? Make sure the copper is annealed before forming, then the from should (might) work harden it enough to turn.
Tellurium copper is very free-cutting if you can find it in cored stock close to that size. Alternatively, punching out a blank then mandrel mounting a stack to turn the OD to size as you mentioned sounds feasible. The ID is obviously not too critical.
For the chamfer, perhaps you could mount a shallow fixture on the mill to locate the ID to a height of 0.077", soft clamp on the outside, then use a flycutter with a bit ground to the chamfer angle and just bring this down to a fixed stop? Then flip over and do the other side?
Yes, the punch and its anvil make the inside by expanding a to thick but to small diameter washer to a correct thickness and to large od washer.
Ascii art: __punch_________ \___/ | ___ | |------/ \--------| anvil the punch anvil form the inside chamfer and also push(cold flow) the copper against the outside wall of the anvil. If the punch had a 'sticking out' piece it would also remove the flash from the middle. think of a brake tube being flared, that sort of idea, only pushed flat might not work of course, but iirc copper is quite 'squishy' when annealed.
The sketch looks like a high vacuum seal to me, if it is I would try to buy from a supplier of such things.
If you want to make it, I feel that a closed die coining operation is the best chance - cutoff varying lenghts of blanks and coin them in formed and hardened dies. It will take considerable GFA and annealing to get it right.
I don't even understand the drawing but then I never can work out engineering drawings. Is the washer 1/8" thick or 0.101" thick? Is the chamfer on the inside or outside?
Anyway my advice would be don't touch it with a bargepole. Let some other poor sod bugger about with it.
I used to have a bad habit of taking on "interesting" jobs too. The intention is that they make a change from the routine and keep you motivated but they always ended up taking forever and costing me money. I've since grown out of the habit.
With outside temperatures of around -3C for the last few days, a challenge in the workshop, even if I don't make anything on it, is more appealing than routine cold steel in the dry-dock, with added icicles
Start with the hardest copper tubing you can find, and use a form tool on each side. Anneal them after, if the use is as I expect.
Got a 5C expanding mandrel that you can use? Conversant with wax chucks? Willing to make a one time use mandrel?
The scan is shitty, but it is plain that the only reason the 1/8" dimension is there, is to define the location of the angle. The information is excess to needs, really, as the agle and depth of the bevel are given.
The draftsman that put this down also managed to get the scale right out of proportion, too, as the .054 flat in the middle came out looking narrower than the two .024 depth bevels. Picky picky picky, I know, but I do find it so much easier to do a job if the drawing looks like the part. :-)
I would proceed thusly. Use stock a little larger than the OD required, with a little spare on the ID. Cut the ID, part off the rings. Place ring on mandrel. Cut OD. Bevel edge, flip to other side, repeat.
Copper is a PITA to machine. Bevels via form tool or cross slide angle. Holding via whatever works for you.
I don't see this one as a tough job, just one that is not going to be a fast one, as the fineness of the parts dictates light cuts.
They're actually seals for a fuel injection pump, diesel fuel at circa
2000 psi. It's a crap design, & not been made for 30 years but I have someone who has need of a quantity. Also may need a few myself.
Yes I know there's 'too much information', but it's a 1930s or 40s drawing, a bit late to shoot the draughtsman. Problem with using a hard grade of copper is that the finished product needs to be as soft as poss. Fine if it's just work hardened, but not so good if it's an alloy. Don't know much about copper myself....
ATM I'm making a punch & die for finishing, I'll se how I get on with that route now I've started. If that fails, I'll try your way
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