How "hard" should it be...

[exsanguinate]

I was successful in hardening my scrape blade, but I need some advice on how to test for "drawing the temper".

After the initial heat treating, I placed the blade in a vice and attempted to bend it. It just snapped and broke. I then took the blade and placed it in an oven at 400 deg for 1 1/2 hours. Then, I placed it in a vice and same thing, it just broke. It may have felt that I used more pressure to break the blade (may have flexed a bit), but that's very subjective.

Is it normal for the blade to break? If so, how much should it flex before breaking? Does a higher RC equate to a more brittle blade, hence prone to breaking?

 

[Crayola]

Ex...., I will help you as best I can. Higher RC values do make a harder blade, which is more brittle. A "scraper" blade I assume should be hardened as hard as a regular knife. try putting a file to the blade you made. If your file is new it should barely scratch the material, if at all. Files are something like RC 62.

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"Come What May..."

 

[vaquero57]

Crayola is right. I do not know what a "scraper" blade is though. I believe a properly hardened blade will still break unless differntially heat treated to give it a soft back. It just will not break as easily(more flex) I guess to give you an answer to your question what kind of steel is it? After the quench and it cools down test a file to it. It should skate off without even biting it. Then the higher the oven temp the lower the rc will be. I believe it is the temp and not the time in the oven that does this. The reason we leave them in the oven usualkly for an hour is to ensure that they reach the temp throughout I believe. When done from the oven the file should skate off but bite just a little. Of course how hard you want the blade shgould depend on personal prefewrences and application of the blade(intended purpose). This will also help you determine if you want a soft back or not. An option is to have someone rockwell test the blade and if you want it harder or softer then adjust the oven temp on the next one. Sooner or later you will find what you like. I have not had any blades rockwell tested yet. I just use the instructions on the steel wrapper and an oven thermometer to make sure oven is accurate then test with file when done. Sooner or later I will have a blade tested though. I think it is a good idea.

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" I am a shootist."
Clay Allison
" Does this mean we are bladists?"
Vaquero57
McAlpin Bladesmithing

 

[exsanguinate]

I am using 1095. The scrap (sorry about the "e" in the first post) blade was my first attempt with my new coote's, which I really messed up

I tried the file, it scratched the scale off, but it really didn't bite into it. I tried drilling the blade, but the bit really didn't grab.

On my first attempt to heat treat, the blade didn't get hot enough. I could easily flex an edge on a piece of brass. On the second attempt, no such flexing occurred. Based on this, can I assume if I get the steel to the correct temp(1475deg)/color, by it's makeup, it should harden to RC 66 and if I do not get it to the correct temp (1375 deg), it will not harden at all?

 

[Howard Clark]

1095 will harden from as low as 1400 reliably if quenched in water. It is better (safer) to go a little bit hotter if you are doing this with relitively simple setups (no temp controls). The as -quenched hardness should be about HRC 62-63. You can get HRC 65 with 1095, but it is difficult, and there is no need to do so.

I would suggest 1400F, quench in water that is 110F (just starting to get uncomfortably warm to the touch), quench for only as long as it takes to get the piece cooled, as soon as vibration and steam bubbles stop, get it into the tempering heat source, whatever that may be. If you want HRC 58 you will need to temper at 450F or maybe a little more.

Tempering is time *and* temperature, not just temperature.

Oil is safer, and if you stay at the bottom end of the austenitizing heat range (1400F) then it will work ok so long as the section thickness is not much over 1/8".

It should skate a new file after quenching in either case (oil or water for quench). Do not hesitate after quenching before you temper, this is when cracking occurs most frequently (especially with water quenches).