Barrel Pin Material

[Lostsheep]

I need a little help here. What material is appropriate for making your own barrel pins?


My google-fu has brought up a couple of of choices:


S7 tool steel (but I do not have an accurate way to harden after turning diameter down;is that even neccesary?)
Drill blanks (don't know where to get them?)
Precision ground 4140 dowel pins

or

Just buy them at $3-$7 (not my first choice given that I need quite a few)

[tigerfu]

I need a little help here. What material is appropriate for making your own barrel pins?


My google-fu has brought up a couple of of choices:


S7 tool steel (but I do not have an accurate way to harden after turning diameter down;is that even neccesary?)
Drill blanks (don't know where to get them?)
Precision ground 4140 dowel pins

or

Just buy them at $3-$7 (not my first choice given that I need quite a few)

Drill blanks (or drill rods) is a no no. It is hard but brittle, and it will shatter under shock.

4140 is good choice.

Another option is case hardened mild steel.

Hope this helps.

-TL

[Gunsmith Dan]

First question before you even get into materials is what type of lathe do you have, will it hold a machine tolerance of +/- 0.0005 or lower?

Firing pins should be made of a Steel that has give like a 4140 or 4130 because of the force and shock involved will cause to hard of a metal to crack/break over time.

Also sometimes "Spring Stock" rods (find them at Brownells) are not a bad choice either. Just remember if you get them really hot to anneal them afterwards or they will be to brittle.

[Lostsheep]

First question before you even get into materials is what type of lathe do you have, will it hold a machine tolerance of +/- 0.0005 or lower?

Firing pins should be made of a Steel that has give like a 4140 or 4130 because of the force and shock involved will cause to hard of a metal to crack/break over time.

Also sometimes "Spring Stock" rods (find them at Brownells) are not a bad choice either. Just remember if you get them really hot to anneal them afterwards or they will be to brittle.

My lathe is not a problem; +- .0002" on a good day with our old chucker. +- .0005" all day long on our prototrak.

4140 would be super easy as Mcmaster has it as cheap as $3.16/ft for 7mm ground stock. Has anyone else gone this route?

ETA: Thanks for the quick responses

[kcstott]

Nop no lathe needed when you can buy the stuff on size ready to use with a precision ground finish. just cut it to length, harden, draw back and install
I use O-1 tool steel Letter "J" for standard 7mm barrel pins. "N" for .300 reamer, and 5/16" for a .310 reamer.
4140 or 4130 would be Ideal but it is not meant to be flame hardened. It does work but it is not the correct way to do things. O-1 can be heat treated with a torch dunk in oil then draw it back.

O-1 is plenty strong enough and very forgiving on hardening. It's very hard to screw up. Ands it's cheep. McMaster will ship you enough rod to do a lifetimes worth of AK's for less then $20 shipped.

[Lostsheep]

O-1 is plenty strong enough and very forgiving on hardening. It's very hard to screw up. Ands it's cheep. McMaster will ship you enough rod to do a lifetimes worth of AK's for less then $20 shipped.

01 it is. Couple of questions though:

I ASSume I should heat until it is glowing prior to the dunk; is that correct?

How deep do you think the hardening will go? Obviously the outside will harden but I ASSume that the center will not be as thorough.

[M1NM]

Drill blanks (don't know where to get them?)

Industrial Pipe & Steel in South El Monte.

http://www.ipstool.com/

[hermosabeach]

Red hot

01 it is. Couple of questions though:

I ASSume I should heat until it is glowing prior to the dunk; is that correct?

How deep do you think the hardening will go? Obviously the outside will harden but I ASSume that the center will not be as thorough.

One shop that invisit uses rare earth magnets with a bowl of oil below the part

Heat the pin until it is glowin red

When it is red hot it stops being magnetic and falls into the oil bath below.

I don't know if this is the right way but it is one way

[kcstott]

01 it is. Couple of questions though:

I ASSume I should heat until it is glowing prior to the dunk; is that correct?

How deep do you think the hardening will go? Obviously the outside will harden but I ASSume that the center will not be as thorough.

Heat it up until carbon fakes for on surface. Usually bright red. Quench in oil and clean and draw back till straw color to light brown.

Hardening is all the way through. you don't run into a softer core until you get into large diameters like 2" or bigger.