Trigger bar tempering question

[wvmtnman]

Over the past few weeks I have been making a set of double set triggers.  I am now getting down to the finishing part of the the process.  I used mild steel and need to temper them.  What I am really worried about is the notch on the front trigger that acts as a catch for the rear trigger and the part of the rear trigger that fits into that notch.  I don't want this part to wear. 
What process would I use to accomplish this?  I have no experience doing any type of tempering and only have access to a brazing torch.  I searched and turned up little on the subject.  Any help would be appreciated.
                                                                  Brian

[KNeilson]

I can answer this as a metalworker (hardening steel), but not a gunsmith. You need to case harden your components. A common compound for this is called kasenite. You heat your parts red and dip in the powder and heat again then quench. What is happening is the steel needs carbon to harden, mild steel does not have enuf and the compounds like Kasenite will add some to the surface allowing it to be hardened. This is done by quenching from a red heat. Now you will temper (controlled softening) by slowly heating to color the parts .  Yellow/straw for cutting tools, blue for impact, springs or wear in your case too.. If you dont temper after hardening the parts may fail from being too brittle. Hope this helps.............Kerry

[California Kid]

kn you are on the right track, but if wv's parts are mild steel they will only be hard on the outside to prevent wear. Inside will still be soft and not brittle, therefore tempering is unnecessary. The case is not thick enough for the parts to be brittle enough to fail. IMHO

[northmn]

Kaenit would be the easiest.  On a case hardening project I do not temper as it is a surface skin.  Kasenit is available through ML supply houses like Track.  The only thing is that whn you quench do not use cold water, use warm or even hot water.

DP

[Woodstock]

OK, Ya got me.
What keeps the mild steel from being brittle in the center after heating to red and quenching? Is it the lack of carbon or something like that? I am planning to case harden all the steel parts as I finish up my current project. How do you know what type of steel you have? I have used the Kasenit in practice on scraps and a few tools I have made. It seems to work real well and is not hard to do. However, when quenching, were your protection and do not place you face over the top of the bucket but rather keep low to the side. And most importantly, be prepaid for a very loud snap crackle and pop. If you are not prepaid for that, you could very well wind up with a brown spot in the shorts. I now know its coming but it still gets me every time.

[rich pierce]

There are a couple of ways of determining if you have carbon steel or mild steel.  The easiest is to try to harden it by heating to beyond magnetic and quenching in transmission fluid.  Now see with a file it if got hard.  If not, it was mild steel.  The other method is by looking at how it sparks on a grindstone.  Lightly touch a non-working part of an old tool like a hand saw, file, axe, chisel, etc. to a grindstone to cast a nice stream of sparks in a darkened room. See how the sparks fork multiple times like the very devil's pitchforks?  Now do the same with a piece of tie wire.  The sparks should differ in color and not fork much at all.

This is all complicated by the complex steels available now.

[Jim Kibler]

A couple things to consider.  While you may get by using Kasenite, the resulting case is quite thin.  A better approach if the triggers are made of mild steel is to carburize them.  This is often accomplished by pack hardening them in charcoal or other specialized compounds.  This creates a case of much greater depth and durability.  If pack carburizing, I would definitely plan on tempering thin parts such as set triggers regardless of what the base material is. 

[Acer Saccharum]

I agree with J Kibler. The parts should be pack hardened. The depth of carbon is way more that you will get with Kasenit.

My concern with the Kasenit is that any stoning of the notches will take the hardness off. Kasenit goes only .002 deep. With pack hardening, the carbon can go .04 or more, depending on time in the pack at temperature.

Tom

[Woodstock]

 Thanks,
Again you are correct. I re-sharpened some tools I made from some stock at the big box hardware store and the hardness was gone in a flash. The lock was the main thing I want to harden. I will probably send it off to someone to have it done. There are too many variables I have read about and too many things to go wrong. Warped lock plate, cracked frizzen etc… I would like to have it color case hardened. You guys know anyone one that can do that? From what I read, it does not seem to be that difficult but I do not feel comfortable with it.

[g.pennell]

I've used these guys several times with complete satisfaction on single shot cartridge rifle actions and parts.

http://www.classicgunsinc.com/

Greg

[KNeilson]

 For the items I have been making from scratch, which are mainy cutting and impact tools, I find it much easier to use a steel with a fair carbon content as opposed to "casing" be it by using a compound or pack hardening. There are so many easily abtainable scrap steels that have a fair carbon content. My favorites are car springs and axles , the older the better. Also I have access to large industrial saw blades, both are .5 C or more. This being said I have changed techniques of heat treatment often to suit the "purpose" of the item being made. With a trigger bar I would think wear is more a concern that ultimate tensile strength, and depth of the case would be an issue as several others have noted. This is where I should probably shut up as I have never made a trigger bar yet. If you have access to a heat source and some type of hardening compound you may be able to experiment a bit by using a bit of the SAME metal in size and thickness and repeating the casing process to try to increase the depth of case (.010 max with Kasenite), although I agree that the pack method is better, it requires more than a brazing torch...

The case is not thick enough for the parts to be brittle enough to fail. IMHO 

California Kid, I would agree, didnt consider the "core".......  Kerry

[Ken G]

Brian,
I've wondered about using mild steel for double triggers myself.  I'm finally building myself a rifle I intend to keep so I thought this would be the perfect time to try and see how they hold up.  i used some of the steel bar you can buy at Home Depot or Ace Hardware.
I just case hardened them as suggested.  Heated cherry red, non-magnetic and quenched in tranny fluid/motor oil mix.  I'm not 100% sure whats in my oil quench pan.  Put them in an altoid tin full of the same oil mix and lite the oil off with a propane bottle (outside) to temper.  
Cheers,
Ken

[wvmtnman]

First off, let me start off by saying that I don't know anything about the types of steel out there.  What type of steel are Davis triggers made of?  I have put together a few kits and hardened them per the directions.  The steel I used was not overly soft.  When filing it works very similar to the Davis trigger kits I have built in the past.
I got the steel from the welding shop that is located in the school where I work.  In passing, I asked the welding instructor what type of steel it was. He said it was just a mild grade he gets from his supplier for stick welding.  I think it is actually pretty durable and takes a fair amount of effort to file. 
Tomorrow I will ask the specifics about the steelOn a side note, what grade of steel would be best for this type of project?
                                                                            Brian

[Ken G]

When doing something for a customer I use 1095 spring steel. 
http://www.brownells.com/.aspx/pid=390/Product/EXTRA_WIDE_SPRING_STEEL

[Dphariss]

Over the past few weeks I have been making a set of double set triggers.  I am now getting down to the finishing part of the the process.  I used mild steel and need to temper them.  What I am really worried about is the notch on the front trigger that acts as a catch for the rear trigger and the part of the rear trigger that fits into that notch.  I don't want this part to wear. 
What process would I use to accomplish this?  I have no experience doing any type of tempering and only have access to a brazing torch.  I searched and turned up little on the subject.  Any help would be appreciated.
                                                                  Brian

Buy some Kasenite and case harden the parts. Heat them red  and coat with the compound and hold at high read for a couple of minutes then quench. Using water with Potassium Nitrate in it will often provide color if the coating is not to heavy on the part. Heating for excessively long periods may make thin parts brittle by through hardening.
Casehardening makes for a very slick surface.
Propane torch will work for small parts.
Dan

[smylee grouch]

All this discusion is good but i have a very related question, if i was to use spring to fashion the triggers, i asume you would have to soften or anneal it befor drilling and shaping . When i drill the hole for the pin, do i use a highspeed drill or some standered drill?  Then when completed, would i need to kase harden the spring steel if it is already a higher carbon content?   Thanks.   Gary

[flehto]

On simple, single triggers that have been cold forged from low carbon steel, the area of the trigger bar that contacts the sear bar has a piece of  A2 air hardening  steel high temp brazed on. The A2 hardens at orange heat and is  62-64 RC. The A2 insert is then ground and polished to a minimal gap engagement w/ the sear bar. Have done many this way and all have performed well......Fred