Everyone has their own way of doing it. Usually caseharden the bottom half of a mild steel extractor. This is where it pivots and the cam strikes it. Center-fire extractors don't have the offset of a rim-fire and strength is not usually an issue. Make sure a file will still cut the upper half after casehardening. Otherwise, it is not mild steel and you will have to draw some temper.
Chuck

  You don't want to case harden parts willy nilly. First you should determine if the part is low carbon steel that will benefit from case hardening and quenching in water or is it a high carbon steel that will go brittle hard all the way thru if water quenched.. First thing I do with unknownium steel is heat and quench a small section and try it with a file..(Actually I use a Rockwell Hardness tester). If it remains soft then it gets the Casenit.. If it gets hard its still unknown alloy but heat treat it as if it were a new spring will probably give you what you want.

If you remember steel beer cans either you drank beer at a young age or started drinking beer much younger than I did. 

When parts are made from junk steel it is tempting to copy the part with steel of a known quality. 1018/A36 are low carbon steels but respond to case hardening. 8620 is a triple alloy steel that is easy to heat treat and will also case harden easily. I usually case harden with the parts encased in a box packed with charcoal and BaCl2 as an activator. Check out the Harris equation for carbon diffusion vs temp. If you don't want case color you can harden in the box. Let cool and then heat in a salt bath and quench. If looking for max hardness then quench in water or brine (pretty drastic). Oil should give you a decent hardness. Temper in the kitchen oven at 300 for a couple of hours. 


Remember, ..... "not everything you read on the web is true"
                         /s    A. Lincoln

Will the forging process soften the file enough to file? 

If you want to slow the cooling process, fill a metal coffee can with play sand and cook the sand in the oven at a high temp. After heating the new part, put it in the hot sand and let the whole thing cool down in the garage for a day.

Jesse

Thanks for the replys. I think we went slightly astray.The original extractor was OK but just soft and I thought that case hardening it would add some rigidity and wear-ability  to it. I have decided to make the rifle into a .22 so the extractor is for decoration now.I am using a Crossno liner but there are some things I don't like about it. So--I have decided to make my own to fit this rifle only, so I have control over how it is made. I have already made a new firing pin in the shape of an 'I' so I would get more reliable 
ignition. I have the tools to do pretty much anything. One of my other interests was small shop tools and having had a friend in the business of selling used home shop tools I have filled the basement. The Bridgeport in the picture took a year to restore/rebuild to what I wanted. The second DRO under the big DRO I made from a scratch and it shows spindle speed-Quill travel and Knee travel. The Servo power feeds came from the junk pile and were rebuilt by me, most had bad circuit boards or broken gears, I now know more than I want to know about them, getting the info out of Servo Products was the hard part.
Thanks for all the replys, interesting about the files.
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Can't tell the date the original side cover for the base was missing and the serial was on there. Most likely late 40-50's was in a lot of 5 my friend bought and had the best table abet the short table. This one was my first and is my backup and I do know the date -Waltham Watch Tool Company--1898 Universal mill and it has all its original drive and head, but is too fast and noisy so the Bridgeport 'M' head on a bar where the horizontal overarm goes.. I am proud of both of them, but that is another story.

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