Using Hollow Punch

Suggest you invest in a hand punch, one of the Whitney No. 5 Jr. clones. You can't put a hole too far from an edge, but they work just dandy. The HF unit has metric sized punches, but 5/32" isn't too different from 4mm. See:

GWE

Hollow punches are for leather. Or for punching holes in canvas to put grommets in.

As grant says, for sheet metal, a Roper Whitney No. 5 junior cant be beat. I have had mine for close to 30 years now, and it still works great.

IIRC we used to use a solid, square ended (slightly tapered) punch on sheet metal to make holes for rivets. Place the sheet over a block of lead (or end grain hardwood, but lead is better), place punch on mark and strike smartly with a hammer, the slug is driven into the lead block and gets liberated upon re-casting. Gerry :-)} London, Canada

Thanks for all the suggestions (now regretting getting too excited and purchasing hollow punch set online).

I also have a need for a sheet metal disc of variable diameters. I tried cutting one using a hole saw with my drill press but found the 2" disc it cut to be basically 'torn out' of the sheet (one big bur). Is this due to a lack of WD40 oil while I cut it? Did I try to cut it too fast? Is there something better to use for cleaner discs than a hole saw?

How can I get nice clean sheet metal discs?

(I'm trying to make my own sprockets by using layered sheet metal.)

Thanks again,

-Bkennedy

You are learning! Your design idea which sounded simple, might not be .. you may have to go back to the drawing board. To cut discs cleanly on a drill press (don't even think about a hand drill) you would need a flycutter and a specially ground HSS bit called a "trepanning bit". To cut discs cleanly in industry is done with big punching machines, faster than you can even think.

WD-40 is worthless as a cutting oil on steel. It might work OK on aluminum, being largely kerosene.

Grant

Layered sheet metal is not a very cheap, or easy way to make a sprocket. Or much of anything. They use the technique to make transformers, but for totally different reasons.

I would be slicing the final thickness you want off of round bar, with a small 4x6 horizontal bandsaw- its gonna be cheaper and quicker in the long run, and the bandsaw is good for a million other things.

Yes, you could cut circles in 16ga with a flycutter- but to do it in much quantity, you would probably want a milling machine, with a collet system that actually locks in place with a drawbar- nothing quite as exciting as when you flycutter overpowers the friction fit of your morse taper drill chuck, and decides to go for a spin around the shop.

On 23 Jan 2007 19:51:09 -0800, b_t snipped-for-privacy@hotmail.com penned the following well considered thoughts to the readers of rec.crafts.metalworking:

Find a circle shear...