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Up Topic Welding Industry / Welding Fundamentals / Punching 5/8" thick Stainless Steel Plate
- - By jwright650 (*****) Date 09-20-2013 12:01
Have any of you guys had any trouble punching an 11/16" x 1.875" slot in a piece of 5/8"thick A240 Type 304 Stainless Steel plate?

I was wondering if regular punches and dies for A36 will shatter if used on this material.
Am I being overly cautious here?
Parent - - By aevald (*****) Date 09-20-2013 13:33
Hello John, that combination, from my experiences is very possibly on the limits of the punch/die capabilities, yet, it would also depend on the clearances of the punch and die too. If you are running a 1/32" clearance between the punch and die you will likely have the nicest hole, yet, if you can run a 1/16" you will likely notice less resistance when the punching process is initiated. I have also been taught that for mild steel the hole diameter minimum can be equal to the thickness and that when you are working with stainless steel a 1/16" over the thickness is the way to go. I additionally believe that since this is a slot that it will help with the required support for the punch and allow the additional "meat" involved to provide an added safety. Additionally, in my experiences, the 304 takes more "umph" to punch than say a 316 grade, but that's just an opinion, I can't back it up with an official reference. Also, be sure to be liberal with your lubrication medium and carefully line-up and retain the alignment of the punch and die. Just a bit of information for your consideration. Good luck and best regards, Allan
Parent - - By jwright650 (*****) Date 09-20-2013 13:45
Thanks Allan. I appreciate your input. I have seen those punches shatter in thinner materials and workers have to dig slivers of steel out of their flesh....I really want to avoid personal injuries if at all possible. I had asked our Purchasing department to pre-order these plates from someone with equipment to perform the work safely and have them cut to size with the holes/slots already in them...well they got part of it right, they came in cut to size, but missing the slot. We don't have saw blades or drill bits that stay sharp long enough to work with this material. We just don't have the equipment in place, nor do they want to purchase it. As much as I try to educate myself and our estimating department about the general issues of working with stainless steel in a carbon steel shop it all seems to fall on deaf ears. None of the concerns associated with this material seem to bother anyone but me.
Parent - By TimGary (****) Date 09-20-2013 15:44
Hey John,

I know what you mean about flying slivers.
I had to send one of my guys to the hospital a while back to get a punch sliver cut out of his bicep that penetrated 1 1/2" deep.
We were very glad it didn't hit him in a worse place...
Granted it was because he changed to a larger punch without changing the smaller die, but we all learned two valuable lessons that day.
1. Make sure the die is the right size for the punch.
2. The sheet metal guard that slides up and down for access to the punch, or for plate alignment doesn't work worth a damn if you leave it up all the time.

If your equipment is not guarded, now might be a good time to make one.

Tim
Parent - By jwright650 (*****) Date 09-20-2013 15:25 Edited 09-20-2013 18:00
OK, we tried a couple...it works, but wow, it sounds like a rifle shot. A bit unerving standing close to it, but it punches. It bends the plate right much, but that is just the way it is going to have to be. If my math is correct the machine should have enough guts behind it to do this.

I figured it would take 59.5* tons to punch this using the forumla below. Our Ironworker is a 110/140.
[edited tonnage*-used 65ksi instead of 75ksi]

Slot was also revised to 11/16" x 7/8"...so that helps a bunch

American Punch says to figure the tonnage required, use this:
Constant = 102 for 65ksi, 118 for 75ksi, 134 for 85ksi
Z = Length - Width
A = Width
L = Length
W = Width

Round = Hole size x Material Thickness x Constant = Tonnage Required
Oblong = [(.63 x Z) + W] x Material Thickness x Constant = Tonnage Required
Square = A x Material Thickness x Constant = Tonnage Required
Rectangle = (L + W) x .64 x Material Thickness x Constant = Tonnage required
Parent - - By jwright650 (*****) Date 09-20-2013 15:46
Got 20 punches out of the first punch before I had a broken punch laying on my desk. Hoping it was just "that" punch, because we have a bunch of these things to punch...they happen every 28" around the perimeter of this project times 3 floors and the roof.
Parent - By aevald (*****) Date 09-20-2013 17:20
Hello again John, just a few other things to keep in mind when you are working at the "limits" so to speak: be sure that the punches/dies are slugly set in the machine (recheck tightness often) everything will seat in after a number of punchings and cause loosening of the set-up as work progresses sometimes. The stripper on the ironworker is a very important aspect of the process as well, it has to be set square and plumb to the plate being punched. This is sometimes a contributor to punch failure when retraction is occuring and one side or the other of the punched plate contacts the stripper and forces it out of plumb/square it will break the punch. Punching near edges of materials is often a contributor to this and requires a "fork" to be used to insert between the part being punched and the stripper allowing for complete support of the punched material and even contact with the stripper. Good luck John and regards, Allan
Parent - - By welderbrent (*****) Date 09-20-2013 17:22
Ouch, I'd be looking for some back up punches asap. 

If the punch was already used it probably had a rough edge going which is not good on SS.  But you will definitely not get as many holes out of them on SS as on CS. 

Good luck, work safe.

Have a Great Day,  Brent
Parent - - By jwright650 (*****) Date 09-20-2013 18:01
I was checking our inventory a few minutes ago....finger crossed that what we have will last until we can get all of these out of here.
Parent - - By jwright650 (*****) Date 09-20-2013 19:42
Made that last punch last through the batch of plate that we have so far...lots more to come though.
Parent - - By welderbrent (*****) Date 09-20-2013 20:54
He said as he wiped the perspiration from his brow...

Have a Great Day,  Brent
Parent - - By Stringer (***) Date 11-05-2013 01:01
I believe a water jet may be a better solution. Not plasma at that T. Kerf problems not worth the material set-up costs, so the water jet is the right tool, I think.
Parent - - By Dualie (***) Date 11-05-2013 03:17
A high capacity laser could make quick work of that also
Parent - - By jbndt (**) Date 11-16-2013 05:56
John,

It's been a long time since I've had to punch stainless but ...

I recall having to use a 'special' lube that had better qualities than the stuff we used for carbon steel (40 wt motor oil).

Warning ... We didn't dare use it on carbon steel due to the price!  :eek:

Your punch supplier should know about it.

Cheers,
jb
Parent - By jwright650 (*****) Date 11-16-2013 11:12
Guys we made it through that job without incurring any injuries(thank goodness!). It had me worried with all the noise that punch made as it passed through that plate....and the broken punch set early on. We did use a spray lube(not sure which type or brand) on the punch and that helped some, but it was still a bit un-nerving to hear that thing go off like a rifle shot each time.
Up Topic Welding Industry / Welding Fundamentals / Punching 5/8" thick Stainless Steel Plate

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