What's new
What's new

Transfer Punches for Thin Sheet Metal

jcorsico

Aluminum
Joined
Feb 17, 2009
Location
Maryland
Hi -

I have an application where I need to transfer existing holes in relatively thin sheet metal (about 0.040") to other parts for drilling. I have a nice set of Spellmaco transfer punches, but the sheet metal is so thin that the punch won't align with the hole (in other words, the point on the punch is much taller than the thickness of the sheet metal, making the transfer punches no better than a regular punch).

How should I handle this? I don't have drawings for the sheet metal parts (and, even if I did, I wouldn't trust that the existing holes are actually where they were supposed to be).

Thanks,
Jon
 
Turn a small piece of metal the same size as the hole in the sheet metal, with a smaller hole in the center, Make the center hold match a transfer punch that you have or turn yourself a smaller transfer punch.

Dale
 
Set your part to be duplicated on top of some thin (3/16"-1/4") foam rubber and set that on top of the material you want to mark. Clamp lightly on edges and then use transfer punches normally.
 
I have a set of transfer "plugs" that I got in a lot of used aircraft sheetmetal tools. I have never seen any for sale. They resemble, more then anything, short flush rivets, except at the 'head' there is the little sharp 'tit' like a transfer punch would have. The shanks are sized to common aircraft drill sizes, #40, #30, #21, #27, #10 and a couple of 1/4" . They don't look 'shop made', as they have some sort of oxide coating. The shank sizes are very accurate, a light 'thumb press' fit into a drilled hole. They are useful when you can't get the strap duplicator into position. ( mentioned above)
 
Hi -

I have a nice set of Spellmaco transfer punches,

That, IMO, is an oxymoron :) I don't like commercial transfer punches, sloppy fits, over sized pips and unnecessary long....I make own as needed.

take a piece of drill rod, turn exactly to size, without disturbing it turn a very small pip. get the pip red hot and quench, i don't usually even bother tempering. won't take 5 minutes.

in use, if you want an accurate transfer, the punch has to fit the hole well and then apply the lightest of taps, don't go wailing away on it, that's what the prick followed by centre punch is for....just make the lightest of marks so that a prick punch can pick it up
 
I have a set of transfer "plugs" that I got in a lot of used aircraft sheetmetal tools. I have never seen any for sale. They resemble, more then anything, short flush rivets, except at the 'head' there is the little sharp 'tit' like a transfer punch would have. The shanks are sized to common aircraft drill sizes, #40, #30, #21, #27, #10 and a couple of 1/4" . They don't look 'shop made', as they have some sort of oxide coating. The shank sizes are very accurate, a light 'thumb press' fit into a drilled hole. They are useful when you can't get the strap duplicator into position. ( mentioned above)

Interesting. I'll try some aircraft supply houses.

The strap duplicator looks like it could work as well.

Thanks very much everyone.

As a backup, I'll just turn my own mini-transfer punch, or a bushing to use my existing punches, as mentioned above.

Jon
 
There was an article in Machinist's Workshop about a year or so ago (Chuck St. Louis, "Not So Poor Man's Transfer Punches", v. 21, no. 5, Oct/Nov 2008). The author made "transfer bushings". Say you want to transfer the center of a 5/16 hole in 0.040 material. Get a piece of 5/16 CRS, which should be slightly undersized. Face it, center drill, drill a 1/4 inch hole about 1.5 inches deep. If you want good accuracy, drill undersize and either ream or bore to 0.250 with some allowance for a sliding fit using your 1/4 inch transfer punch. Part off (about 1.25 inches in length), chamfer inside holes slightly, break the edges ever so slightly (just so the darned thing doesn't slice you to ribbons when you use it). Put this in the hole and use your 1/4 inch transfer punch.

Or use an appropriately sized socket, with an appropriately sized punch guided by the 3/8 inch square (or 1/4 inch, depending on hole and socket size).

The author demonstrated a neat idea. He drilled and counterbored a hole in some scrap. Slide some 1/4" drill rod in there and ox-acetylene heated it. Let the drill rod drop down so that the red hot part was a bit above the surface of the scrap. A couple of whacks with a ball pein hammer and he had created an upset head. Put a transfer point on the other end. Some annealling, cleaning up, and heat treating followed. This part was used in the body of a Starrett Snap punch as a "snap transfer punch", and was used with his set of transfer bushings.

Hope these ideas help.

Jim
 
Try transfer punches for threaded blind holes called Transfer Screws...small machined hex screws with precision points. Or blind hole spotters. McMaster sells them
 
Last edited:
Best to place the thin sheet over the thicker steel and wipe with water, so it transfers to the steel below.

Then wait nine years, the age of this thread. The rust should show right where to drill . . .



Optical center punch -- with the concentric centering circles -- would have been another answer, back in 2009.
 
Try transfer punches for threaded blind holes called Transfer Screws...small machined hex screws with precision points. Or blind hole spotters. McMaster sells them

The OP clearly stated the material was .040 thick.....Duh.
 








 
Back
Top