Making a pistol part

[Bmi48219]

I found out the hard way it's not a good idea to let the hammer drop full force while the slide is removed from an AMT AutoMag III. Bent the part of hammer strut that goes into the hammer spring. It bent where it meets the tombstone shaped piece about 30 degrees. I straightened it out but a crack has started where it bent. Not having a lot of luck finding one, High Standard, Numrich, Midway & Brownells are out of stock. Thinking about drilling & filing one out of suitable thickness cold rolled steel strap.
I figure the hole for the pin is pretty critical, diameter-wise, but if the strap thickness is the same I think I could drill first, then trace the old piece and file away until it matches. Am I looking at this wrong or are there any things I should be considering?
The part on right is like mine, 'tombstone' section is 1/4 x 1/2 inch roughly. I didn't mike it yet for hole diameter or thickness. The outer edge on one side is slightly thinner/rounded making me think it was a stamped part. Any suggestion would help.
173982

[Artful]

Have you done a hardness test on the existing part?
Oh, and I'd radius where the strut meets the tombstone, cracks like to start at corners.

[Der Gebirgsjager]

I'd like to try to help, but need a little more information. You haven't explained the photo too well. Where does it come from? What do the numbers represent? You said that your part is similar to the one on the right? Can you get the part on the right and file and/or grind it to be like yours? That would beat starting from scratch. As for the tail that goes inside the spring, although they should be close things that work that way often aren't exact. The shaft/tail needs to be polished so the spring will compress around it smoothly and expand smoothly. Of course larger in diameter won't fit, but a bit thinner will probably still work.

[Ballistics in Scotland]

Yes, modifying the part on the right, if available, seems like the way to go. Alternatively drilling an oversized piece of metal first, and then filing or grinding it to shape, is probably better than drilling a nearly finished one. Between metric and the US number and letter drills, you ought to be able to find one the right size. eBay is probably the handiest source.

https://en.wikipedia.org/wiki/Drill_bit_sizes#Number_drill_sizes

It might be that you could repair the one you have, if you know someone who can do MIG or TIG welding. You would have to be able to file or grind a v-shaped groove to the depth of the crack, without the part dividing in two, and fill it with weld.

Or you could probably get silver solder into the crack without the filing. Possibly there is enough room for a washer to be soldered over the joint like a short collar, to strengthen it. Here is a piece of high speed steel soldered onto the tip of the automatic safety actuating rod on my Gibbs shotgun, ready to be smoothed off. That part is loaded purely in compression, with a lot less force than a mainspring, and the rest of it was retained in its original hardness by pliers and copper sheet during soldering. So I am far from sure soldering or welding would work for you. But if you have the solder, what do you lose by trying?

174007

Most steel described as cold rolled is mild. That may be fine, as long as you only fire it with the slide on. But mild steel isn't hardenable except by case-hardening, which doesn't much reduce the resistance to bending and cracking where yours did. If I was making one from scratch I would use some form of hardenable steel.

A higher-carbon steel can be heated red-hot and quenched in water, then tempered (well enough for a spring, which is better than you need) by immersing it in a small pool of oil which you ignite and allow to burn away. There are air-hardening steels which become hard without a liquid quench. As good as anything, though, is O1 tool steel, which isn't described as air-hardening, but acquires a degree of hardness which is probably fine for this part, if you just heat it red-hot and hold it on a piece of wire to cool evenly and quickly.

[MarkP]

If you know someone that has access to a water jet have one cut from tool steel (flat gauge stock). Place the part on a scanner import into a cad program and create a drawing file.

If you need some help let me know I could create the Cad geometry for you. Send me a PM.

[44man]

I would start with a piece of oil hardening tool steel rod. Turn the tail and then shape the other end, drill and make the hole to shape.
Harden and put in the kitchen oven at 300-350° for an hour, turn the oven off and let cool.
Rod is dirt cheap from Enco or such.
Soft steel just wont do. Silver solder will soften the whole thing and you can't harden again. It will keep bending and wear. The part is so small, tig will affect it too.
I made longer transfer bars for my Rugers and BFR's so I could get lighter triggers, using the kitchen oven method my SBH has had 81,000 heavy loads with no change.
I made one once where it was not quite right, the hole in the trigger was different so I heated that end to shape and neglected to re-harden and temper the entire thing. It BROKE. Hours with a hacksaw and files wasted. Never neglect hardening and tempering.
You might get away with a spring temper, draw temper in the lead pot at 600° for an hour with a slow cool down on the pot edge after you fish it out of the lead. I opt for harder for that part.

[44man]

Stay away from air hardening steel, too hard to temper. I really like oil hardening and use transmission fluid.
Turning air hardening can make it hot enough to harden and even carbide will not cut. The small tail will ride the cutter and you will ruin it. Never start with hard steel either.
Yes, you need a lathe or a friend with one. You will be surprised at what you can do by hand too. I have a Browning BPCR that had the wrong hardness on the cheap trigger with a steel insert in an aluminum trigger that failed. I made a new trigger out of tool steel and it has been perfect for years. Tempered in the kitchen oven. I even added an adjustment for pull.
Just start with a good steel.

[Ballistics in Scotland]

That is true, that you can't simply turn that slender collar on a lathe with a cutting tool in the same way as you would a shorter or stouter one. You could do it by the rather laborious process of reducing the first quarter-inch or so, step by step, and then the next quarter-inch and so on. It wouldn't matter, if it is simply to fit inside a coilspring, if there is an almost imperceptible stepup in diameter at each stage. If it comes to that, filing the tongue to round would probably do.

[Bmi48219]

First I want to thank everyone for their advice. My knowledge of steel grades & properties is limited.
In the image I posted the part on the right IS an actual hammer strut for a model 3,4 & 5 Automag, just like the one I need. Also while I don't know the procedure to test hardness, I know mine is soft enough to impact bend the tail 30 degrees without breaking. It appears to be a stamping as the perimeter of one side is slightly rounded and the other side completely flat. The tail is square sided, not turned. A local machinist is making one for me (mild steel) to try out. I would like to learn how to test the original part for hardness for future parts manufacture .
Considering how the original part did bend, and looking at the way this part functions, I don't know that hardness is really critical. As long as the hammer isn't allowed to pivot too far forward, which can only happen if the trigger is pulled with the slide removed, the strut isn't subject to a bending force. Under normal circumstances the primary wear area has to be the lower portion of the pivot pin hole in the strut.
I am going to give the new part a trial and see how it hold up. Meanwhile if anyone can explain how to test steel hardness with limited resources I am really interested.
thanks again

[44man]

No need to test, just go by temperature after hardening to temper.
If the part is soft, a file will cut easy but if hard it will squeak. As hardness changes, a file will change how it cuts.
If a part cracks when bent straight, it had some hardness.
Rockwell testing is a little beyond what we can do.
Since the hole in the part rides a pin or strut, it can wear. It is not that the part needs to be real hard but to keep it from wearing.

[Bmi48219]

44man,
i am going to have a new piece soon, machined out of what will probably be some form of mild steel. I can probably find out the grade of steel when I pick the part up. Would you mind going over the process of hardening & tempering? Also, and please forgive my lack of knowledge, what is the reason for tempering a hardened piece?
Thanks

[44man]

Heat the part with a torch, propane good enough for small. I hold with wire that will not melt. Get it good and red and hold for a time. Drop into oil. Keep the part straight going in so warp is reduced. I use Dextron oil.
When cool, clean it off, put on a small pan in your oven at 300° for tool steel hardness and 350 to 400° for softer. Spring steel needs 600° and a lead pot is best.
Temper softens the steel to what is needed so it is tough and doesn't break. Turn the heat off after an hour and let the part cool with the oven or pot.
You can't harden soft steels except case hardening and that will only be the surface that can absorb carbon.

[BigEyeBob]

If you're getting it made form mild steel you wont be able to harden it by heating and dropping into oil . You can how ever case harden it with a powdered substance called Cherry Red . Doing it this way will harden the surface but give a softer core .This will give the part some flexibility with out the tendency to crack or fracture .

[gunshot98]

Google outbackgunparts. Great bunch of guys. They probably have it.

[Bmi48219]

I had a local machinist make a new hammer strut for my AutoMag III. Actually he made three. Two from mild steel & one using 4140 grade. I installed one of the mild steel struts and ran 500 rounds through the pistol. Just removed & inspected the strut, no signs of wear and the strut / hammer pin hole still appears to be true & round.