Best Heat Treat Alloy For Minimum Distortion After Hardening

[Paul Alciatore]

My experience with hardening is limited. But I may want to make a punch and die for use with sheet aluminum (1/16" thick or less). I will need some shapes that are more complicated than a simple circle so I would need to machine those shapes in both the die and punch before hardening. I am thinking about some relatively small holes to start with, probably in the range of 1/2" to 3/4" (12 to 19 mm). My grinding equipment and skills are limited, so I would like to keep the after hardening grinding to a minimum. So, what would be the best, heat treatable alloy to use for minimum changes in size and/or shape?

I don't have an oven so I would probably need to heat it with a torch and then quench. So keeping the hardening process simple would also be desirable.

[elf]

Quench technique might be more important than the alloy type. Get one of these.

[Paul Alciatore]

I do not see how an induction heater relates to the quench technique. Can you explain? Or are you making two different suggestions?

Quench technique might be more important than the alloy type. Get one of these.

[Erich]

D2 is what you seek

I believe the answer for your situation is D2.

http://www.cintool.com/catalog/High_Carbon/D2.pdf

Note it is intended for punch and die work and it has minimum distortion.

It mentions to temper above 900F to avoid a contraction during tempering. 925 F is your target.

This sounds like a job to send out to a heat treat shop. Your not going to get best results with a Torch and D2.

[Spin Doctor]

In my experience the most distortion free I've used has been O-6 or A-10. Trade names Graph-Mo and Graph-Air. The A-10 is probably less risky simply because its air quench. Both machine like butter. The easiest machining tool steel I've ever used. Comes from Latrobe Steel. They are or were part of Timken. As I understand it these steels are used in the production of Timken cups and cones.

[Bob Ford]

If you are punching less than 300 times I would consider 4140 HT. Add a lube when cutting. About 3-5 degrees relief.

Bob

[Mcgyver]

My grinding equipment and skills are limited, so I would like to keep the after hardening grinding to a minimum. So, what would be the best, heat treatable alloy to use for minimum changes in size and/or shape?

Not wanting to grind suggests an air hardening steel like an A2 - no fast quench creating distortion. However its more expensive and you have to get it a lot hotter than O1. 1800F vs 1500F.

If fairly simple and squat, I'd just make it of O1 and see how it goes. I've made countless cutters over the years including spindly shapes like square and hex broaches and just never had an issue with distortion. it is obviously going to 100% depend on the part and the tolerances you need to hold and how accurate the punching has to be.....but its not like everything made of O1 turns into a banana and is useless without grinding. Also there is fair bit of clearance with a punch and die

[wierdscience]

+1 for A-2,it's easy to get and easy to heat treat. I've done plenty of quickie parts with a torch,but it's a big help to buy a few firebricks and stack them into a simple furnace so the part can heat in it's entirety to the correct temperature.Doing this the results will be much more uniform.Later if you decide to build a heat treat oven you'll already have a few bricks.

[Bob Ford]

have made a lot of gas check dies. From .22 to .45 cal. The first were made with 1018 and lasted more than 2,000 uses. The blank that is cut for a .45 is about .56. The die cuts and forms the blank into a cup in one operation. This is on .010 to .020 Aluminum , copper, or brass. Unless you are going to use the dies for high production I see no need for trying to harden and temper with what you have to work with. 4140 HT should give you good service. Relieve the dies behind the cutting edge and give a small rake angle and you should be good. If you are making a KO type than you will need a way to line up the dies.

Bob

[Tundra Twin Track]

I have made some Drill Collets out of Precision Ground 4140 17mm OD with varying ID's what would be best way to harden these to avoid distortion.No experience with this.

[anddsn]

A2 or A10 Would be my choice. I use it a lot at work for some very close tolerance dies that bend or shear . I rarely have to do any grinding except for the face for a shear edge. A2 is easier to find and you can find it in many different shapes, and machines fine. I believe A10 is only made by one company and usually found in round form, it has graphite in it which gives it excellent machinability graphite also gives it an anti galling attribute. Both grades hold their size very well when heat treated due to air quenching. A10 hardens at a lower temperature 794 C. and A10 at 960C. I wrap them in a stainless steel bag when heat treating.

[Jaakko Fagerlund]

I have made some Drill Collets out of Precision Ground 4140 17mm OD with varying ID's what would be best way to harden these to avoid distortion.No experience with this.

Vacuum chamber, read: Sub it out.

[Paul Alciatore]

Are you saying to just machine it and forget the heat treat? Yes, this tool will only see occasional use in my shop.

BTW, I have done a bit of research with chassis/knockout punches. One thing that I found was that a bit of grease is the best way to ease the punch through. It produces a noticeable reduction in the amount of force needed to punch a given hole. I always apply it to the punch, to the threads on the draw bolt, and to the face of the nut that seats against the punch unless it is a ball bearing version. I like to use a moly grease. I believe it also helps to keep the cutting edges of the punch sharp.

If you are punching less than 300 times I would consider 4140 HT. Add a lubewhen cutting. About 3-5 degrees relief.

Bob

[Bob Ford]

Paul,

4140 HT is about 30 R.C. It is tough, but relatively easy to machine. Sharpe H.S. tools are fine. Can be tapped easy.

See post #9 I had used 1018 to try out the design. It held up surprisingly well.

Bob