Suitable steel for making a lock plate

[Don Tripp]

The recent thread on Southern Rifle ideas made me think about the options that are available to builders of left handed rifles. While our selection is better than ever, it's still less than what is available to right handed or right eye dominant shooters. Back when the Large Siler was the most prevalent lock in either configuration I was always amazed at the various styles that could be made from it. Now we have the Gunbuilder's Siler that we can shape without the restrictions of the original lock plate. Since I have accumulated enough Siler internals over the years to make a few locks I was wondering what would be a good choice for steel to use for the lock plate. I'm surrounded by steel mills and one mill has an outlet store for their odd lots and random sizes. Currently they have tons of 1018 cold rolled available and I picked up 6' of 2" stock that is the perfect width for a lock plate. The Siler pan fits with just enough resistance to be tight. Is 1018 suitable for this purpose or is there a better choice? I am aware that the cast square plate is available for $19 or whatever but I can get 1018 or other steel for $1 or less per pound.

[Bob Roller]

I make caplock plates from 1018 but mine are milled from 1/4"x1-1/4 or 1-1/2. It works well and is readily available from a variety of suppliers as you have found.

Bob Roller

[Acer Saccharum]

1018 works well. The lockplate will need casehardening.

[44-henry]

I would generally stay away from cold rolled steel. Because of the way that it is manufactured there are a lot of internal stresses in the material which can cause it to warp when being machined. Hot rolled mild steel would be a better choice.

[Acer Saccharum]

8620, a low carbon steel would probably work well, too. Casehardens nicely.

1018 can be annealed, and stress-B-gone.  Hot rolled sometimes has inclusions of carbides and other junk, but it would work well, too.

[Stophel]

I've made lockplates from plain, ordinary, cold rolled mild steel from the local welding shop.  Works just fine.  It's relatively soft, easy to cut and file and drill and hammer on.  Case harden it and you're good to go.   

[Bob Roller]

I anneal the 1018 after I cut the bar into the lengths I use for lock plates and have very little warpage. I have also use a good bit of low carbon flat ground stock and have no problems with warpage or stress relieving after removal from the mill's vise.I have had unannealed plates literally hop out of the vise when the pressure holding them is released.
I have found inclusions in hot rolled steels that were hard as a diamond and could and did wipe out brand new end mills.
I made the bolster breech for my 50 caliber N.Lewis copy from 8620 and it machines easily and takes nice threads.

Bob Roller

[flehto]

If a cold rolled steel is used, it's best to start w/ a piece twice as thick as needed and remove approx. equal amounts from both sides to avoid warpage.....Fred

[James Wilson Everett]

You might try the original material, wrought iron.  In many respects it is better behaved than any steel.  Go get an old barn hinge at your local antique shop. 

Jim

[JB2]

Wrought iron?  As in old wagon 'tires'?  I know where a couple are, and just waiting for me to pick them up now that I have a use for them.

[Don Tripp]

Too many scrap yards that supply the steel mills around here. There is no wrought iron left in this area except for the fence around the cemetery downtown. The place that I got the 1018 from (http://www.alro.com/Locations/Locations_JZ.aspx) is a good source of very pure hot rolled steel too. I didn't consider internal stress when I thought about using cold rolled. I appreciate the good advise. I haven't built a gun in 8 years and the part of my brain that I used for that is full of cobwebs.

[camerl2009]

simply annealing will not remove the stress from steel it has to be normalized idk what temp for 1018 but it will take atleast 3 heat/slow cooling cycles

i do this with all the 5160 i use(it comes from leaf springs so theres alot of stress in it that said i have not had a problem yet with the steel snap from a stress fracture)

[JCKelly]

Stresses in cold rolled 1018 plate or bar certainly do cause it to warp when machined.
Ask me how I know this, from the basement as well as the lab.

Good news is that you can make your cold rolled MILD steel completely free of stress by heating anywhere from 1100 through 1300F.

This is where the steel just begins to glow in poor light, the evening or basement with the lights out.

So long as you don't go above 1300F you don't have to slow cool it.

Well, since temperature control is kinda dicey anyway, just let the thing air cool. That's enough.

To relieve all of the stresses in cold rolled you do NOT have to get it red hot, just get it hot enuff to begin to glow a little. Then let it cool however it pleases, set it on the floor, take the torch away, whatever.

Oh, yeah - the basement. I was filing a 1/3 scale swamped octagonal barrel out of, I presume cold drawn, steel tubing some years ago when - Kink, the end just bent over. I knew what had happened. I am a metallurgist. Sure. Ever hear of the shoemaker's kids? Anyway I took my trusty propane, maybe MAPP dunno, torch & heated the end until it just glowed a bit, then took the torch away. After it cooled, hammered the darned thing straight, problem went away.

Easier to do than beating out a piece of 1/8" plate from that old wagon tire, though yes that's more authentic.

By the way if you intend to case harden 1018 you really should relieve the stresses first, early on so a little scale does not become a problem. Reduces chances of it warping badly when quenched from pack. Which should be on edge, don't belly-flop it.

[Bob Roller]

Jim,
That is what I do with the 1018 I make lock plate from and no problems with it jumping out of the mill vise when I unlock the jaws.
Dull red in bad light and the let it cool overnight works for me. I run the mill at 180RPM and use a 1"x1/2" 6 flute stub mill with TiN coating and it works like a charm every time.

Bob Roller

[Stophel]

Since I'm not "milling" anything, warpage is no problem for me!     (never encountered it anyway.... except for it bending from me hammering on it or something!)

[Acer Saccharum]

JC Kelly, thanks for sharing your experience.

[Don Tripp]

JC Kelly, thanks for sharing your experience.

Yes, and thank you Mr. Roller as well. Whenever I've asked questions on this site I end up learning things that I didn't even know enough about to ask the right question in the first place.