[TheForge] Hydraulic Press Question

[RIES NIEMI]

on 8/13/03 5:27 PM, Woolley at wjande@erols.com wrote:

> Greetings,
> 
> I don't have room nor need for an ironworker in my shop(or the
> pocketbook).  What I would like to do from time to time is punch square
> and rectangular holes through 1/4 maybe 3/8 flats and plate.  Does
> anyone know how powerful a cylinder I might need to do this?  Metal for
> tooling?  I was considering making a chanel frame  to back up the
> cylinder and hold the tooling.  Anyone have any ideas for this set up
> without breaking the bank?  Thanks.
> 
> Regards,
> Bill Woolley

1/2" square hole thru 1/4" plate takes 12.5 tons
1/2" square hole thru 3/8" plate takes 18.75 tons

the formula is   Circumference of cut in inches x thickness of material in
inches x shear strength in psi divided by 2000

so 1/2" square = 1/2+1/2+ 1/2+ 1/2, or 2" x .25 x 50,000 (nice safe figure
for a36, includes a little extra for safety) divided by 2000.

that means at least a 20 ton cylinder. Theoretically the cheapest way to go
is to get a cheap hydraulic jack, say 30 tons to be on the safe side, and
make a beefy frame for it, and get somebody to machine die holders, and use
off the shelf punch and die tooling. I like Cleveland punch and die-
1800-451-4342, for punches. You cant make em yourself for what they charge
for them, precision ground from tool steel and heat treated.
  If you look at what enerpac uses for a 30 ton hydraulic press, you see
that for 30 tons, to be safe, the sides of the press ought to be at least 8"
channel. 12" would be better. If you make it like an "H" frame shop press,
it would be the cheapest way to make a safe punch. You would only be able to
punch things that fit in the throat, but if you were going to build a "c"
frame punch, you would need to cut the c out of at least 4" thick plate,
maybe thicker. Much easier to fabricate an "h". The early scotchman
ironworkers were made like that, with a punch in an enclosed space, so the
widest material you could punch was something like 4" flat bar. They werent
the most versatile, but they were cheap.

All of this is a roundabout way of saying there isnt really a cheap way to
deal with the pressures involved in punching steel. To be really useful, I
wouldnt build a punch that couldnt punch a 1" dia hole in 1/2" plate- that
would be 40-50 tons, about the size of the smaller ironworkers. Then you
really do need to use 12" channel for the sides.
But even if you bought a new, decent brand jack, paid someone to machine die
holders, and fabricated the frame, you could come in for maybe 600-800
bucks. 
One alternative, not cheap, would be to get a "c" clamp style hydraulic
punch- whitney and nitto both make them- they would have the punch capacity
you want, and are small, but probably cost a couple of grand.

Whitney also makes hand powered punches- they look like a really beefy c
clamp, and you have to bolt them down to something that is fastened securely
to the floor, then you put on a big cheater bar and reef. I have a number 20
I got many years ago used, and it is a 20 ton punch. I have it on a base
plate that I bolt to my work table when I need it, stick it under the bench
when I dont.
http://www.roperwhitney.com/punching/2-1011.asp

ries