Making a punch press and dies for small parts

[antleygd]

Any of you use a punch press to punch the starting hole in guard made of brass and 416 stainless? Were the dies custom made by you or did you have the dies made.

 

[Carl_First_Timer]

You can put holes in a part in a single setup on real basic prototype style tooling, though the finished parts have to be manually removed from the tool. The female side ends up being blind with the punch in it, pressing into the male side. The times I've tried this, there often wasn't enough room to mill that feature directly so I'd insert it. You do want some holes so you can knock your part back out. But it is possible to get features in your part with a simple two piece setup. It just doesn't look very conventional and you have to manually remove your part.

It sounds like you've had a lot more experience than me, is there a better (easy) way for something like this?

As far as small holes go, I've had trouble with the tool breaking and have always ended up drilling holes smaller than about twice the material thickness.

Well I am glad someone posted in this thread, as I never saw this post.
What you describe would be about right. When making a production tool we just use include a piece inside the "female" and around any punches and use the Holes to allow a knockout bar to remove the blank. That keeps the part nice and flat.

For The smaller holes, good finish on the diameter, and minimal punch life meaning the shoulder of the punch where it meats the hole diameter size will almost hit the surface of the material. Couple that with engineered die clearances, along with very sharp tools will help. You should be able to get to 1 material fairly easy.

Breaking tools happen for one of a few main reasons:
Initial shock (Compression)
Breakthrough shock (decompression)
Side loading
Pull out load (galling)

Anyway, I wonder if Bill ever got around to doing this.

 

[SteelSlaver]

Having run a punch press a lot and used to be the authorized instructor for the company I worked for. It was strongly advised that you never punch a hole that is smaller than the thickness of the metal and that was with factory dies in a very rigid machine. That was for mild steel. But, I would hesitate to change this rule for something like brass as some of what we think of as softer alloys have different properties when you try to punch them. I used to have a chart that listed the percentage of change from mild steel to a few different alloys.

Over pressuring a small punch can lead to catastrophic failure. We had a guy (dumb azz) try to punch a 1/4" hole through a piece of 1/2" 304 stainless. The punch sheared off and was heard hitting various locations in the shop. If it would have hit him I am sure it would have made a serious hole. When much younger and dumber I was using an older punch press to make slotted holes. The dies worked loose and became slightly mis-aligned. I became aware of this when a piece of the punch slammed into my jaw and embed itself in my gums. It felt like I had been hit with a baseball bat and I thought my face had to be tore to hell. Ran to the mirror, small hole and the boss had to pull out a sliver of the punch that was near buried in my gum. Be careful with this stuff.

Punch presses are great, but, the thing I would worry about on semi-precision parts is the amount of distortion from flat caused by punch pressing. Especially around the edges where the metal is actually being sheared in the operation.

 

[Bill DeShivs]

I gave up on the idea!

 

[scrdmgl]

Hi Nathan:

I know that this an old thread but I wonder if you have building plans with dims. for the simple punch die that you mention in your article. I wish to build a die for punching holes on mild steel and aluminum flat strip with a 5 Ton press. I found a complete source of all the neccessary info concerning Tonnage, Materials, Tolerances, etc.from Scott Machinery therefore I can concentrate on the die construction itself. I intend to provide for an adjustable stock guide for manually feeding the die that I can always incorporate to the die design itself. Given the limited tonnage, I plan to punch up to 1/2" diameter in thicknessess as suggested by the tables and also go for a shear type punch to easy operation and increase punch diameter and thickness within my tonnage limitations. Any info will be appreciated

Thank you in advance

Jorge

 

[Stacy E. Apelt - Bladesmith]

This is an old thread that was abandoned by the OP. If you have specific questions for Nathan, a PM or email would be better. Thread closed.