Really dumb question about heat treating.

partsproduction · Sep 19, 2017

I need to make a handgun sear and have some S7 tool steel, but the minimum charge for heat treating has really spiked recently.

So my question is what is the minimum equipment needed to heat treat S7? I had a HT oven once but sold it many years ago, now I have only an acetylene torch. I see muffle NG furnaces cheap in ebay, would that suffice? Would those cone things be good enough to set temperatures? I think S7 needs to be held at temp for a time. I have plenty of steel for experimentation.
Thanks in advance.
parts

Davis In SC · Sep 19, 2017

For S-7, a furnace that will go to 1750F, and a file are the 2 basics needed... But in reality, that furnace should go to 1900+ so you can do H-13 and other metals. A roll of stainless foil is a necessity, as is a Rockwell hardness tester.
S-7 is a bit sensitive to soak times, most S-7 HT failures I have had are due to short soak times. No major disaster, just re-heat treat the part...

Illinoyance · Sep 19, 2017

Unless you plan on heat treating a lot of parts, just bite the bullet and pay the heat treat shop. The cost of setting up to do it yourself would make that one really expensive sear.

As Davis said, you really need a hardness tester. In addition you should consider a second furnace for drawing the temper.

Limy Sami · Sep 19, 2017

Change you material? ..like 01 gauge plate, ......lot easier to HT, and only being a small part will be easy ..............and probably what they were made out of in the first place AKA nothing fancy.

Just my 2 cents

michiganbuck · Sep 19, 2017

Had a small heat treat shop do a one-up job for me, He ran it with other work and charged me zip..I gave him $20 for a tip.

partsproduction · Sep 19, 2017

I have a good hardness tester.

The cost of setting up to do it yourself would make that one really expensive sear.

As often as I want a small hardened part I have to disagree, stainless foil shouldn't cost too much, and I suspect that a $100 muffle furnace would possibly be settable for temperature within wider tolerances, maybe I could buy a probe and gage too. I sure regret selling that electric furnace, but as most folks know by experience anything not used much, if it occupies much space, is a negative. One of those muffle furnaces doesn't occupy much space, and if it would work I could store it.
I sent two small parts to a HT place recently for case hardening, they would easily fit in my trouser pocket, $309. The minimum used to be $75, at that price I could almost bear the price for a sear.
I'll do some research on natural gas muffle furnaces and whether they will work for this.
In oregon the regulations have become so extreme that many businesses are closing and that may be the reason for that price.
Thanks for the responses, I think I'll look further into this. The O1 idea is another one I may use.

TDegenhart · Sep 19, 2017

partsproduction said:
I have a good hardness tester.

As often as I want a small hardened part I have to disagree, stainless foil shouldn't cost too much, and I suspect that a $100 muffle furnace would possibly be settable for temperature within wider tolerances, maybe I could buy a probe and gage too. I sure regret selling that electric furnace, but as most folks know by experience anything not used much, if it occupies much space, is a negative. One of those muffle furnaces doesn't occupy much space, and if it would work I could store it.
I sent two small parts to a HT place recently for case hardening, they would easily fit in my trouser pocket, $309. The minimum used to be $75, at that price I could almost bear the price for a sear.
I'll do some research on natural gas muffle furnaces and whether they will work for this.
In oregon the regulations have become so extreme that many businesses are closing and that may be the reason for that price.
Thanks for the responses, I think I'll look further into this. The O1 idea is another one I may use.

In my experience, your $100 furnace is going to be more like $700 to $1000 with controls. You mentioned heat treating and carburizing. These are distinctly different processes. You can pack carburize in a small air furnace but almost everything is done in an atmosphere furnace, a whole different animal.

partsproduction · Sep 19, 2017

You mentioned heat treating and carburizing.

That was just an example, the minimum charge shot up a great deal in the last five years to my best memory.

Davis In SC · Sep 19, 2017

The best part of in-house HT is the time element.. If I can make/harden/grind/ a part in a day or 2, and get a machine back running... It is worth a nice premium over the one to 2 week quote...

rogertoolmaker · Sep 19, 2017

partsproduction said:
I need to make a handgun sear and have some S7 tool steel, but the minimum charge for heat treating has really spiked recently.

So my question is what is the minimum equipment needed to heat treat S7? I had a HT oven once but sold it many years ago, now I have only an acetylene torch. I see muffle NG furnaces cheap in ebay, would that suffice? Would those cone things be good enough to set temperatures? I think S7 needs to be held at temp for a time. I have plenty of steel for experimentation.
Thanks in advance.
parts

Changing to O1 steel is an excell

rogertoolmaker · Sep 19, 2017

Change to O1 as suggested in a previous post. A Sear is a very small part that can be harden with your torch. Set your torch for a carborizing flame and heat slowly and evenly to a slight bight red 1400 deg.
Polish with emery to clean. You can draw to proper temper in your kitchen oven. 400 degrees = 60 Rockwell. A very light straw color.

Roger 09/19/2017

partsproduction · Sep 19, 2017

Set your torch for a carborizing flame and heat slowly and evenly to a slight bight red 1400 deg.

Let air quench then? Quench to room temp or start temper from a slightly elevated temp?
This sear is not available in gun parts houses, I've looked, a bit of a rare gun in America.

Astra 4000 Falcon.

The reason I was thinking of S7 is because the original half cock tip broke off, and it was only 46 RC.

S7 is supposed to be more shock resistant and should work well at normal sear hardness, 56 or so. But I have no idea how the original broke, it's a new gun to me.
Thanks again for the help. I may go to O1, but I keep wondering why it broke, and normal practice when something breaks is to go to a better material (If it can't be redesigned).

TDegenhart · Sep 20, 2017

O1 is an oil quench steel. How old is the gun? Its possible that the original part was case hardened

Tom

Toms Wheels · Sep 20, 2017

Heat treatment on small parts inhouse is in my opinion a smart thing.There are temperature controllers cheap $40, yeah chinese. But they have lasted 3 years in occasional use. One is used in a toaster oven that is used for tempering, the other in an electric HT oven. They regulate the temp very well.

PM if you like more info.

partsproduction · Sep 20, 2017

O1 is an oil quench steel.

I thought of that later, so is 4140 which I harden here often.
I downloaded the app "Heat Treaters Guide Companion" yesterday.

I've always hardened small parts in house when they are oil or water hardening, but I'm still thinking S7 would be more shock resistant, and we have a lot of it here from the last job we did.

Of course I missed my chance there, that box of parts went to the HT and that was the $309 charge, not the two small case hardened parts I mentioned (Those cost $190 to case harden, I got them mixed up in my memory).
I should have made up the sear then and shipped it with the other S7 parts to the heat treaters, I'm sure they would have hardened and tempered them with the batch for very little added.

One thing about setting out to make a part by a new method, it may in truth cost much more than paying to have it done, but one also gains much more in experience and confidence for later, and another option for customers as well.

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