Filing new sear on Marlin 1894

[Depreacher]

One of my customers brought in a Marlin 1894 new model in .357 Mag. It had a 1/2 lb. trigger pull according to my rcbs gauge. I do not like to do trigger jobs, and normally will replace the sear, hammer, or both with new lawyer pull triggers. This is an early model that Marlin has discontinued selling the hammer (it's the narrow one). The old sear was rounded off, so I bought a new one. The new sear is too tall to let the hammer come to full cock. It almost makes it, but not quite. After carefully filing it down, and getting a good 4 to 5 lb. pull, I need to harden the surface. Brownells, and Midway are both out of Kasenit. I thought about Heating it to a dull red, then quenching in 30 wt. motor oil. Then setting the oil on fire in a small container and let it go until it burns out. Used this for springs in the old days. Any ideas????????? All help is appreciated. THANKS, Mack

[Bullshop]

Sounds good to me until the part where you burned off the oil.
I learned about oil quenching when I used to pick up scrap steel at the Clempson Br. hack saw works in Middletown NY. At that time the quenching process was all done by hand at timed intervals. Each blade went through a heat/quench process that repeated about three times per each blade.
I used some of the flat stock scrap I got there to make tire irons for motorcycle tires. I heated and oil quenched just once and those bars became springs. You could pry a tire off a rim and get them bent into a half circle and they would just spring back straight. Before quench hardening you could double them over with your hands.
I would try just the quench then see if a file will touch it. The file will tell you a lot about how hard it got.

[longbow]

Not sure what grade of steel the hammer is but it would have to be at least a medium carbon steel to harden much by quenching. If the hammer is high carbon or alloy steel for hardening then it would most likely require tempering after quenching or it will be brittle.

You could easily check the old hammer by filing. If it is soft except on the wear surfaces then it was case hardened. If it is hard all over then grind part of the surface off, heat red then quench in water. If the ground surface is hard the hammer is carbon or alloy steel. If not then it is low carbon steel.

I am not sure but I would suspect that the hammer is low carbon steel and the sear surface is case hardened or possibly the whole hammer is case hardenend. Case hardening is not normally tempered as it is a thin case of very hard material over a ductile core.

If you can't find Kasenite or equivalent, you might try packing the hammer in charcoal in a closed (but vented) container then heat red and hold at red temperature for an hour or so. Then take out of your furnace and drop the hammer into water to quench. This should form a thin case hardened surface.

I have done this for reamers where I did not have high carbon steel handy so used medium or low carbon steel baked in charcoal for a while then quenched. They were hard enough to cut mild steel after.

Colour case hardening was done in much the same manner but using a mix of materials like leather, charcoal, bone, etc. packed around the part, heated then quenched.

This is a lot more work than using Kasenite though!

Longbow

[Depreacher]

THANKS for the info, Bullshop and longbow. Actually the hammer is just fine, it's the sear that I have to file down so it will snap into the hammers full cock notch when the bolt overides it. As is, it's just a mite too tall. I should have clarified that. The original sear looks to have been rounded off, and would be too short if reshaped. Sorry about that. Mack

[Depreacher]

Filed the sear this morning. Got a firm grip on it with a small vise, then used an 8" file, and finished with a fine India stone. Pure luck, but the trigger pull came out at 4.5 lbs. on my gauge. FINALLY found Kasenit on Track of the Wolf's website. $13.95 + $8.95 UPS. It's on it's way here now. THANKS for the help men. Mack

[MtGun44]

You need to heat treat by quenching in oil or water from red hot. This makes the steel hard
at the max level it can attain - but it will also be very brittle. To trade off some of the hardness
for toughness instead of brittleness, you need to temper it by heating again to a much lower
temperature, like about 700-800F depending on the alloy.

A fairly good way to get the temper roughly right is to use "tempering colors". You have seen
polished carbon steel turn yellow, then blue and then purple as he heats up. These temper
colors are easily seen when grinding a piece of steel as it gets hot from grinding. They occur
at very specific temperatures. Polish the sides of the sear and gently wave the tip
in and out of a propane torch until the sides just start to go from the yellowy color
to blue. ONce you get blue you should be there. Too hot and it is back soft. We are
talking about subtle oxidation colors on the surface, NOT any sort of glowing from
heat. This is way lower than red hot. The colors are permanent, unchanging as the
steel cools back down.

Bill