Making new punches for punch and die set

[ddmckee54]

I scored a punch and die set off Ebay for a very reasonable amount.

http://www.ebay.com/itm/20095238206...NX:IT&_trksid=p3984.m1497.l2649#ht_209wt_1185

It was used, but handmade with great care. It's set up for punches ranging from 1/16" thru 1" by 1/32's and in some cases by 1/64's. It was a little rusty and very grungy when I got it, but a lot of elbow grease took care of that. I still have to get a new dowel to replace the missing guide pin but the set is in pretty good shape now.

As you can see it's missing a few punches. I don't have the equipment to make new punches fron scratch so my plan is to cut the end off the appropriate drill bit, harden the business end, and then sharpen it to use as a punch. Maybe even rig up something to grind a relief on part of the punch just like the rest of the set.

How can I tell if the steel used for the drill bit is air, oil, or water hardening. I'm guessing it's probably water hardening, since the easiest way to heat just the drill flutes would be induction heating with a water quench.

Anybody got any more information or bright ideas?

Don

 

[MachineTom]

MHB, suggests Carbon Tool Steel, hardened to 57-60 C. So look at the branks you are buying to see how to get it that, close anyway. What size press do you have for the punches. A 1/2 punch in 1/8 steel is 5 tons to punch, even steel sheet .062 would need 1.7 ton.

Offhand Formula Steel punch force: hole(inches) X thickness(inches) X 80= tons force to punch hole. For brass use a factor of 65 rather than 80.

 

[ddmckee54]

This will be used for shim stock(probably under 0.010"), gaskets and maybe some sheet plastic(probably under 0.030"). We're talking fairly light duty here.

Don

 

[abby]

Then why harden ? generally only one is hardened , the punch is hard and the die soft or the other way round , depends on whether you want the hole to size or the slug.
Drills are HSS they cannot be easily hardened , I believe they are nitrided in a cyanide salt bath.
If you have cheap carbon steel drills you are wasting your cash as they won't last very long , didn't think even the Chinese still made 'em.

 

[ddmckee54]

That's why I asked about making the punches. I'm relatively new at this, dusting off the tools after too many years, and forgot that drills are usually HSS. This set won't see a lot of use, just once in a while when I need to make a gasket or shim. The die is definitely hardened, a file won't touch it. In the future when I need a punch I don't have, I'll try the drill bit route to see if it works.

In a perfect world, how would you make a new punch? Remember this is for light duty one-off's, not for production purposes.

 

[Swifty]

Don, you can reduce the pressure required to pierce through the material by grinding a shallow angle on the front of the punch. Piercing .010" material only requires a similar taper on the punch, and you have halved your piercing pressure.

I had a similar one at work and we used ejector pins that are available from toolroom suppliers, they come either through hardened or nitrided, either will do the job. They come slightly under nominal size, about half a thou.

Put the material in and give it a sharp hit with a hammer, you will be surprised at the force this gives.

Paul.

 

[ddmckee54]

Thanks Paul, I never thought of using ejector pins. I'll have to check into them. I had read about grinding an angle on the punch and have been thinking about what I can cobble together, I mean build, to accomplish that.

Don

 

[abby]

Don can I just point out that that you do not appear to have any way to locate a punch over it's die with the material between, A hardened punch will damage the die if not perfectly aligned so I suggest soft punches would be safest.
Even if set up in a press the punch could move enough to hit the die edge , this is not a problem with a soft punch , they are often made slightly oversize and forced into the hardened die for a perfect fit

Here both the die and the 2" dia punch are soft but cut through 20 SWG copper like butter.

The press is a No.4 fly or hand press giving up to 11/2 tons of whump

In this case the discs were required not the holes .

 

[Swifty]

Abby, the plate is actually 2 pieces located together with dowel pins, with a gap between to place the material to be pierced. The top appears to be acrylic so you can see where you want to pierce the hole. This type of jig is mainly used to make thin packers, with the holes pierced to allow for screws to go through. The slugs that come out are waste.

Paul.

 

[Swifty]

Drills are HSS they cannot be easily hardened , I believe they are nitrided in a cyanide salt bath.

Just for general information, HSS is hardened at a higher temperature than normal carbon steel, and it requires a different method to temper it after initial heat treatment. HSS has properties that hold the hardness even when fairly hot, like after grinding, so you can imagine the difficulty trying to temper it. Not sure about the current method for initial heat treatment of drills, they may now use some type of inert salt bath, or better still a vacuum furnace.

Cyanide salt baths are no longer used in Australia, not sure about the rest of the world, they were just too dangerous. Stories about heat treaters having syringes with antidotes for cyanide poisoning were always told, not sure if it was true. Most nitriding is now done in a sealed atmosphere furnace using gas. A nitride depth of .005" takes overnight in the furnace to achieve.

Paul.

 

[Swifty]

MHB, suggests Carbon Tool Steel, hardened to 57-60 C. So look at the branks you are buying to see how to get it that, close anyway. What size press do you have for the punches. A 1/2 punch in 1/8 steel is 5 tons to punch, even steel sheet .062 would need 1.7 ton.

Offhand Formula Steel punch force: hole(inches) X thickness(inches) X 80= tons force to punch hole. For brass use a factor of 65 rather than 80.

In calculating blanking pressure for press tools I always used the formula;
Length of cut in inches X thickness of material in inches X shear strength in tons.
Average shear strength for mild steel = 25 tons/sq".

Paul