How to size a punch press?

Looked in my 1943 Die Engineering Layout and Formulas book. A nomogram in the back only goes to 1/4". I checked a 3" circle at 1/8 and 1/4, and it seems to a bit more than double the tonnage. So checked 3/16 and got about 45 tons, to give approx 90 tons for 3/8. Clearance will have an impact on actual tonnage. I'd say at least 100 tons, maybe more just to be safe.

Given that he's got to make dies for everything, might be better off finding a used CNC plasma table?

Jon

3/8" and 3" will take a 100 ton unit for steel.

Maybe hunt up an Ironworker with the large punch option, those will take up to a 4" punch. New they run about 16K. Should be able to find a used one for 5-6K.

I have a 50 ton that I picked up years ago for 2K in VERY good shape.

He has a mill..claims it doesnt make "round holes"....blink blink.

But the plasma table..that certainly makes a great deal of sense. Id not even thought about that.

Thanks!!!!!!!

Gunner

I just talked to him..and he says he has a $30,000 CNC plasma cutter..and under 1"..the sides of the holes are NOT square.

Its not a "high definition" plasma, but is only a couple years old.

Now he is talking about down to 2" holes in 1/4" plate..max....wish he would make up his mind.

There are some 45 tonners in So Cal on Ebay I told him to check on.

Shrug

Thanks guys

Gunner

Well I was thinking not only of saving the die making time and expense, but the ability to crank out parts as he needs them. He could easily set up programs to make a family of parts in one setup vs X number of setups using dies.

Jon

Multiply the perimeter of the cut by the thickness of the plate, times the shear strength of the metal---Divide by 2,000 to get tons of force required---multiply by 2? JERRY

I think 45 is light for 1/4". I wouldn't put that job on my 60, the whole building would shake. There are tricks of scalloping the die to reduce needed pressure. It will deform the scrap strip. If you scallop the punch, that will deform the blank. I would farm it out to somebody with the right equipment or find a supplier for a standard blank.

Hummm..ok. Thank you for your assistance, this is so far outside of what I know, that its the backside of the moon to me.

Gunner

As I understand it, a punch press typically has a motor and flywheel and clutch. Sizing those for your parts is the task at hand, and... I'd think in terms of building dies and handing them to a shop that has a half-dozen punch presses, and asking for a small run of parts.

The footprint is just the storage rack of the dies, and a shop that keeps a variety of sizes of press can determine the best size for any given part. You get the full benefit of their multiple presses without the monthly upkeep and rent (for a few-minutes-per-month kind of parts throughput).

Many of the modern presses use hydraulics instead of a flywheel. The guy builds dune buggies and race cars and is a full time LA county fireman. So he has a full plate. I know Ive brokered a rather nice LaBlonde lathe and a Bridgeport for him in the last 6 months..so he has to be doing fairly well to be buying tools of this dollar value.

As a lot of his work is done when he is off shift etc etc..he cant depend on needing a Lefthanded Widget made up for him at 4am, when he suddenly discovers he needs one to bolster the trailing watchcallet on the upswept doofunny.

So he needs to be able to do it himself when he needs one.

Gunner

First law of stampings: If you don't need many hundreds of thousands, farm it out! I have nine presses and I STILL farm out low-volume or intricate parts. I'm lucky in that most of my parts are round and thin and the dies are easy to make and last decades...or until an oops.

_Machinery's Handbook_ has a section on the calculation of the tonnage needed for different thicknesses, different hole perimeters, and different materials (brass and mild steel are what I remember being there).

3" diameter is 9.42" perimeter, or about a 3" square for this size. :-)

I somehow don't think that this will be very small or light. If he can be more patient, an eletrically pumped hydraulic press might do better -- but you still will need a lot of metal to support the stresses.

I've got a 1-1/2 ton punch press which I can carry without too much difficulty, but this would be on the order of about 1/4" diameter hole in 1/10" brass - a *lot* less than what he wants. I think that he'll need a fork lift to position what he needs.

Start with your copy of _Machiery's Handbook_ of course. It is almost two o'clock (AM) so I hope you will forgive me for not looking it up in my copy right now. :-)

Good Luck, DoN.

I broker lots of short runs in funny shapes in metals from s/steel to brass to titanium, in thicknesses from 1/16th in to 1/2in plate. i use a laser profiling co. without exception. I either give them a pattern to copy or a drawing. They then digitize it, and laser profile it out. Theres no cheaper or faster way to produce up to say 200 of any one component. Thyey supply the metal as well. Turn round time is usually 5 working days. They allways give me a price up front, and I allways pay on collection. They can digitize up to A1 drawing size. Great co.But there no use your friend as were in the UK. They can also do 3D work on tube up to 4in dia. clever stuff. Ted In Dorset in UK.

No mention of material(s) to be punched/stamped.

3 * Pi * .375 = 3.53429174 3.53429174 * 140,000 (guesstimated mild steel ultimate strength)/2000 = 248 (rounding up) tons. Add a safety & dull punch factor. Shear factor 1.0

See

& HTH