Can I Heat treat A2 as finished sized rectangular punch without screwing up corners

DanBrub · Apr 28, 2020

Been asked to fab a custom rectangular punch and die for an iron worker for customer. I don’t do this kind of work in my shop but he is desperate for quick solution and willing to take a risk. Fortunately he is only Punching 1/8” aluminum bar stock.

I can machine the punch and die from A2 steel and have a small diy made heat treat oven with ramp temp control. My question is whether I can machine the punch to finished size which will have sharp edges on the corners of the rectangular punch and heat treat it without causing problems on the corners.

Thx

otrlt · Apr 28, 2020

DanBrub said:
Been asked to fab a custom rectangular punch and die for an iron worker for customer. I don’t do this kind of work in my shop but he is desperate for quick solution and willing to take a risk. Fortunately he is only Punching 1/8” aluminum bar stock.

I can machine the punch and die from A2 steel and have a small diy made heat treat oven with ramp temp control. My question is whether I can machine the punch to finished size which will have sharp edges on the corners of the rectangular punch and heat treat it without causing problems on the corners.

Thx

I think that it is very possible that you could, my only concern is your ability to properly heat treat this punch. I strongly recommend that you let a pro do all of your heat treating.

TDegenhart · Apr 28, 2020

Unless the dyi heat treat furnace is a vacuum, you will need to put the parts in a stainless steel bag to keep from decarbing the surface. If you air harden, there will be 2-3 thousands of decarb, especially in the corners. Make it oversize and grind to size?

Tom

edit:- What about the die? You could grind the top surface but the throat will have decarb.

McMaster-Carr

McM-C can get these to you in a day or so.

DanBrub · Apr 28, 2020

Believe me if the customer wasn’t so desperate and I so wanting to help I’d let “ professional“ punch and die makers as well as heat treaters Do it all but I want to at least try! No fancy vacuum oven but I do have stainless bags for heat treating, but wondered if A2 air quenching is ok with the part left in the bag.

sfriedberg · Apr 28, 2020

Absolutely yes, you can leave the part in the bag while air quenching. Ideally, you'd start tempering then the part gets down to about 150F. This can be hard to judge in the bag, but if you press the foil against the part you can get a better thermal reading on the part temperature.

gbent · Apr 29, 2020

Have you checked makers such as Cleveland Steel Tool? It may be stock, or quick delivery.

EOLSON · Apr 29, 2020

Absolutely, wrap that thing up as tight as you can possibly get it in a stainless bag and let 'er cook. Give it plenty of time in the oven and temper it back so it doesn't fly apart it'll work just great. Either that or just machine it hard, which is probably what I would do depending on its geometry. Please tell me you have a decent hardness tester though...

DanBrub · Apr 29, 2020

Sure appreciate the willingness of all who responded to give me great advice. The size of this punch For an Edwards ironworker is not standard (21/32” x 13/16”) so doesn’t seem available in my searches which is why I’m even attempting it. I’m assuming for a punch you’d want to optimize hardness and toughness so according to my chart I’d shoot for Rockwell C of 56 (hardening at 1775F and soaking for an hour, air quench to 150F, then tempering at 950F for 4 hours for this sized item).

DanBrub · Apr 29, 2020

We haven’t talked about the die yet. Without a square broach that is the size needed I was hoping I could grind a HSS tool to nibble away the radius left by the end mill. I’d mount the tool in the mill quill and use the quill like an arbor press with the die in the vise. Any better suggestions?

TDegenhart · Apr 29, 2020

Old timers (75-100 years ago) would use the punch to broach the die. One way is to machine the die leaving just a few thousands on the opening but clearing out the relief on the backside. Grind the punch to size plus the die clearance and broach the die. Harden the die and grind the punch to size.

Tom

Thunderjet · Apr 29, 2020

Wrap the punch in tool wrap, hight heat at 1750 for 1 1/2 hours, remove the wrap and let cool to room temp.

Draw back at 500 for two hours, boom your done.

Same with the lower, but remember, your probably going to have around .008-.010 thousanths PER SIDE clearance. the die does need to have dead sharp corners. you could file a 1/8 radius away in about five minutes with a good sharp file.

And get a liability clause worked into the P.O.......Just sayin'

dcsipo · Apr 29, 2020

DanBrub said:
Been asked to fab a custom rectangular punch and die for an iron worker for customer. I don’t do this kind of work in my shop but he is desperate for quick solution and willing to take a risk. Fortunately he is only Punching 1/8” aluminum bar stock.

I can machine the punch and die from A2 steel and have a small diy made heat treat oven with ramp temp control. My question is whether I can machine the punch to finished size which will have sharp edges on the corners of the rectangular punch and heat treat it without causing problems on the corners.

Thx

why A2? If it is a punch in a pinch O1 is an easier option. less decarb and easy quench in oil, The heat threat is also less critical.

dee
']D

DanielG · Apr 29, 2020

If he doesn't need it today and a bit less than a week is short enough lead time, can you order the punch and die from Misumi and just machine an adapter to fit it to the ironworker?

DanBrub · Apr 29, 2020

I have a square punch from the customer cause I wanted to verify relief angles, etc. the clearance between punch and die is almost .016” on all sides. The punch looks like it’s never been used so I’m assuming that is clearance I’m supposed to shoot for. You overestimate my filing skills!

.

rogertoolmaker · Apr 29, 2020

Heat Treat A2

otrlt said:
I think that it is very possible that you could, my only concern is your ability to properly heat treat this punch. I strongly recommend that you let a pro do all of your heat treating.

I'm 100 percent in agreement about sending the punch to the Heat Treater that has the right facilities. Make the punch to finish size. There won't be any problem with shedding the sharp corners during heat treat. Harden 60-62Rc. Sometime we look for trouble where there is none. For 1/8 thick material the punch clearance is normally five percent on each side of the punch, or .006 per side. .016 Clearance is more than I would do.

All The Best
Roger

DanBrub · Apr 29, 2020

Good to know that O1 has less decade. Die is almost 2” dia and I have A2 in that dia so it was the expedient choice

DanBrub · Apr 29, 2020

Good idea but the machine is 2 hours from me and I dont have drawings that would help me fab an adapter

DanielG · Apr 29, 2020

DanBrub said:
Good idea but the machine is 2 hours from me and I dont have drawings that would help me fab an adapter

You have enough info to make a new die though. The adapter is just the difference between the ironworker die shape and the Misumi die shape.

wesg · Apr 29, 2020

Leave it in the bag until the red color goes away. That should eliminate the worst of the decarb.

Stone a small radius on the corners after heat treat, 5 thou or so. A bit of back taper is helpful as well. Its probably gonna be run dry, and this will stop the punch from getting galled up.

DanBrub · Apr 30, 2020

From the die sent by the customer I measured a 1 degree relief taper on the punch so that is what I will machine. Interestingly the face of the punch has a convex shape I assume to reduce the shear forces as the punch comes into contact with the material. I have observed sheet metal punches often have concave shapes so was surprised at the Edwards punch design. It also has a leading conical point which I assume keeps the punched material from moving as the punch begins to engage. It has certainly been an interesting challenge for me as most of my one man job shop work using only manual machines is simple stuff compared to this.

Can I Heat treat A2 as finished sized rectangular punch without screwing up corners

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