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rws
07-30-2010, 09:35 AM
My question revolves around making resizing dies for reloading. I've made them before using stainless, and have sent them to be hardened. They turn out OK, but they aren't as hard/durable as a case hardened off the shelf die.

So my question is, what material would be good? I've tried A2, and it's too hard to ream properly. Need something softer to start with, then have the ability to harden.

What would be REAL nice is if there was something I could evenly heat myself then let cool. That would be cool! I appreciate any suggestions.

squirrel
07-30-2010, 09:42 AM
4140, you must have 2 furnaces and follow the procedure exactly and temper it down to about 50 Rockwell. Also buy the book Heat treatment, Selection, and Application of Tool Steels by William E. Bryson. The book is priceless to someone heat treating.

Bob Ford
07-30-2010, 09:49 AM
Rws

12L14 then caseharden the inside only. Use a funnel shaped attachment to water line. Press hot die against then turn on water.

Bob

rws
07-30-2010, 11:34 AM
Bob,

I've heard pf people using 12L14. From someone who knows squat about case hardening, can you expound a bit on the procedure?

MTNGUN
07-30-2010, 03:11 PM
Most of the reloading dies I've handled were hardened through and through, not just case hardened. That said, case hardening should serve the purpose.

To case harden, you use something like Kasenit. Instructions on the can:

-- heat to bright red (1650 F)
-- dip or roll in Kasenit
-- bring temp back up to bright red
-- water quench
-- repeat process for a deeper case

alternatively, if you have a furnace:
-- bury part in Kasenit
-- heat buried part to 1650, hold for an hour
-- quench in water

Not sure if this applies to case hardening, but if you harden tool steel, it will shrink, and sometimes warp. It is hard to avoid scale, so between the scale and the shrinkage, critical ID's will have to be finished by honing, grinding, lapping, etc..

Mcgyver
07-30-2010, 03:51 PM
4140, you must have 2 furnaces and follow the procedure exactly and temper it down to about 50 Rockwell. Also buy the book Heat treatment, Selection, and Application of Tool Steels by William E. Bryson. The book is priceless to someone heat treating.

Squirrel, can you elaborate on why you need two furnaces? Thanks for the book recommendation but can the curious hear the readers digest of how the process and how it differs from say O1?
thanks

squirrel
07-30-2010, 06:24 PM
You have to start tempering when it reaches 150 F. The higher temp furnace will not cool down fast enough. I forgot to mention 4140 is best oil quenched until it hits 150F.

MTNGUN
07-30-2010, 07:58 PM
You have to start tempering when it reaches 150 F. The higher temp furnace will not cool down fast enough. I forgot to mention 4140 is best oil quenched until it hits 150F.
I don't follow.

Not knowing any better, I've been hardening and tempering 4140 using a single furnace. What am I missing out on ?

squirrel
07-30-2010, 10:08 PM
I don't follow.

Not knowing any better, I've been hardening and tempering 4140 using a single furnace. What am I missing out on ?
I say this frequently, "if it works don't ---- with it". The critical temperature is 150F, it should not drop below that to help reduce poor transformation of the grain structure. Alot of people have different ways to do it, if your method has been working fine for the application I would not worry about.

mcskipper
07-30-2010, 10:09 PM
Never made a case sizing die , but have made bullet sizing dies.
Use 12L14, machines super nice.
Harden W Kesnet. The part will get hard and deep too.
Be prepared to have to lap the inside. I use wood laps.
I just grit blase the outside then treat with BreakFree to prevent rust.

4140 works good for me on some parts like sears.

doctor demo
07-30-2010, 10:27 PM
4140 works good for me on some parts like sears.
Sears, where America used to shop....No, I know not that sears:D

Steve

MTNGUN
07-30-2010, 10:46 PM
The critical temperature is 150F, it should not drop below that to help reduce poor transformation of the grain structure.
I have not been able to find any source that backs up that claim.

I did find this, on a blacksmith site, talking about moving the part into the tempering oven:
Quickly is important. I didn't used to pay much attention to the "quickly" part of this last point – going directly to the tempering operation – but it is important. After we have quenched the part, it is in a very high state of retained stresses and wants to relieve those stress by, you guessed it, cracking. If we move quickly to lower those stresses by tempering, we decrease greatly the level of residual stress in the part and the likelihood it will develop stress relieving cracks.

My guess is that, in applications prone to cracking, it is advisable to quench to no lower a temperature than necessary (that's where your 150 F comes in, other sources say 125 F, other sources say cool enough to touch with bare hands, etc..) and then immediately move into the tempering oven.

I can go along with that, if there is a problem with cracking.

None of my 4140 parts have cracked yet, not enough to notice, anyway, so I'm going to continue using the single furnace method. :D

gwilson
07-30-2010, 10:56 PM
There is another book I had to leave at my former job. I can't recall the title right now. It,too said that for the best tool life,you MUST temper the tool when it has cooled to about 130,or about as hot as you can stand to hold in the hand for a short time. i do that now. I had 2 electric furnaces at work,but you can use a toaster oven,pre-heated to the tempering temp. You cannot rely upon the temperature these,or kitchen ovens will say they are at,though. A kitchen oven can be 75 off. Technically there is only a 25 'window" to get the very best performance out of a tool. I have a Brownell's Gunsmith Supply hi-temp. thermometer with a LONG probe on its back,which I insert in the toaster oven. Then,I get it adjusted to the optimum temp. for tempering the TYPE of tool I'm making.

This process means the most when you are making tooling worth thousands of dollars,but you should be aware of it. I always want things as perfect as possible,so I do it. It can make your knife stay sharper longer,or your plane stay sharper longer. I make punch and die sets for our home business,so,I want as many thousand parts out of them as possible,for the trouble they take to make.