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best way to duplicate hole in bronze?

Hey all,

I am making some small bevel gauges out of 1/2" x 1/16" bronze. They are made of a stack of three pieces about 2" long. On the hinge end I need to get a hole in the same place on all three pieces. I know I can drill all of them at once, but is there a way to punch the hole? To make some kind of jig to get the hole punched in the same spot every time? I can do a decent job with the drill press, but in order to get it right it seems I need to drill twice, and I want to do better than "decent". Any suggestions?

Thanks,

Eide

Reply to
Eide
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Define "the same spot". Within 1/2"? Within 1/32"? Within .001"? Within .00001"?

You can get real close with a punch if you carefully centerpunch and then feel the part onto the tit on the end of the punch, and hold it there while you actuate the punch. That will get you within a few thou of your centerpunch location. If you are good, you can centerpunch within .002" of your desired location, that will get you within .010" - is that good enough?

You'll need an optical center punch to do that good, though.

Grant

Eide wrote:

Reply to
Grant Erwin

Yeah, sorry about the vagueness, I work with wood and most of the time I try to be within 1/8". I don't even know how much .002" is - let's say for this I want to be within 1/128". So, a punch. If I want to use a punch what am I looking for? What kind of equipment do I need? Thanks.

Eide

Reply to
Eide

Well, 1/128" is .0078" which is a bit more than .002" but not that much. Anyway, now you've gotten into the range of ten thousandths of an inch, which rules out a bunch of stuff.

I thought you had a punch already. If you don't, then go get a Whitney No. 5 punch set ($45) or clone ($19). These will punch 1/16" bronze OK.

See e.g.:

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I just looked up the Bay-Com optical center punch I bought for $40. It's now damn near $80. So go have a look at:

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Grant

Eide wrote:

Reply to
Grant Erwin

You need to estimate a couple of things.

1) The tolerance on the hole diameter you are trying to punch. What amount of deviation from a given size can you allow, and what amount of devination from true round is allowed?

2) The tolerance for the hole location. Are you trying to locate the hole in reference to a given edge on the part, and if so, how accuate does that need to be?

the first will tell you what method is appropriate, this could be:

Punching (round and to size within 0.010 inch, depnding on the punch)

Drilling (round and to size within 0.001 inch)

Reaming, etc.

The locational accuracy will tell you what kind of jig you need. If you are punching a diameter to within 0.010 or 0.005 inch tolerance, then your locational accuracy does not need to be more than that, really.

Jim

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Reply to
jim rozen

Thanks for the info. I'll check out a hand punch and see where that gets me.

Eide

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Reply to
Eide

Why not make the bronze pieces a little oversize, drill and ream the holes, then with a steel dowel pins, pin them together and sand them to final size?

Seems to me using a punch and die is not going to get you as snug a hole as a ream. Also the punch tends to cup one side and flare the other.

Reply to
Roger Shoaf

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