Browning Trombone part #15: Firing Pin

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AikiNut

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Hi. I have a bt as in the title, and have made a firing pin for a friend's bt, but of hardened A2. My question... If i make another (wire edm cut to a reverse engineered CAD file from an original) should I use something hardened or not. One colleague has suggested O1, and i see edm cut sears claiming to be hardened s7...

Open to suggestions
 
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I have made one by filing it out of regular sheet steel. It peened and dented before long because it was without hardening. So I made another and just hardened it on front and rear ends by heating with a propane torch and quenching. that worked OK and the rifle is still shooting many years later.
 
Hi, I also have a Fn Trombone with this part broken. I am looking to buy one or if somebody can help me to find someone who can build me one. I don't have the exact plan to do another one. I don't have the front part of it. I found pics of it, so I have the total lenght, but there is a groove in front, and for that, I don't have the dimensions.
 
Well... I have one and can make a copy but I'm still waiting for an answer about what's the best steel to use.
 
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I'd use stainless and heat treat harden it just like a knife blade, try a D2 or S30V, 1950 soak temp air quench.
 
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Hardened and tempered for sure. Of the steels you listed, my order of preference would be; S7, A2,O1, but I wouldn't hesitate to go with the O1 if that was what I had on hand. Your part won't suffer the impact stresses that would absolutely require S7.
 
Waba said:
Hardened and tempered for sure. Of the steels you listed, my order of preference would be; S7, A2,O1, but I wouldn't hesitate to go with the O1 if that was what I had on hand. Your part won't suffer the impact stresses that would absolutely require S7.
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Thanks for that. I currently have a piece of hard a2 left over from cutting out knife punches for muffler manufacturer can also watch for s7 scrap..
We also end up with lots of D2 scrap and occasionally M4. Hard m4 is used to make punches for auto parts makers so I imagine it would be more than needed, too.
 
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I'm thinking that you guys are going over the top with the steel selection. Likely as not the originals were a basic tool steel that was hardened and tempered to a tough spring like nature. So O-1 drill rod or flat stock should be fine. Just harden then temper to the right sort of spring like qualities.
 
That's how come I have ordered a piece of O-1 flat ground... However... "Just harden then temper ..."
I will probably grind to thickness (ordered .125 x 1. x 36 O-1, need .110 at the thickest part) after cutting into three equal length pieces. Then send them out to one of our suppliers for heat treat...
Stack them, EDM drill wire-start holes, and wire-cut (if there's ever a lull in machine time at work - crap we're busy now) a dozen or so copies for hand fitting... One of the guys at work has my pin at present - intent is to scan it and make up a CAD file for the main profile of the firing pin.
 
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So... Now I have a CAD file created using CMM. Currently in MCX7 format but exportable as igs or stp. Have also obtained some 0.125 O-1 gfs which is going out for heat treat (50-52 Rc acc to the tool/die maker for a balance between hardness (resist peening) and toughness (resist breaking)) before being surface ground to .110 thickness. Plan is to stack 3 pieces, 1" x 0.110" x 12", EDM drill some wire-start holes and then wire-cut a "few" (perhaps 30?) firing pins. They'll require some hand finishing to shape the striker part and to radius the little retainer tab that limits movement in the bolt.

If these were to be made available to people, how much should people be paying? I'd test each one in my BT before sending them out... So far, there's $30 in the O-1, an hour driving to pick it up, I don't yet know how much is in the heat-treat, but I'll include that. The wire cut is usually charged out at about $7/square inch or about $85/hour. There's probably about a square inch of cut in each pin (I can work it out but haven't done that yet)...
 
Now have six firing pins for browning trombone, made from O-1 heat treated to 52-54RC. Wire cut to a cad file made by scanning a factory part (from my rifle). One is spoken for. Should I put the rest in EE?
 
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