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Masonry bit knife


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I've been poking around the internet looking for an answer to these questions for a while and have finally caved to - ghasp! - asking for help.
Forging a star bit masonry chisel into a knife blade. Octagonal stock, water hardening etc. I was told by a member of the ABANA guild chapter in my area that tempering the steel of masonry tools was different than tempering carbon or tool steel because of the alloying elements and referred me to a site he simply referred to as "engraph." No luck finding the site or "bethlem super 8" steel, anyone know what he was talking about?

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It is regretable that most companies that make tool steels have created brand names for what are really the standard AISI tool steel chemistries. I could not find bethlehem Super 8 (are you sure this is not a cheap motel?) but if it is a water hardening grade, it would have about 1% carbon, .20 manganese, and about .20 silicon. Having no other significant alloys to retard the tempering reaction, it would temper fast. This means you want to start with a low temperature first. For a knife blade, I am thinking you would probably want a hardness of about 55Rc. Heat to just non-magnetic, water quench, temper at about 600F or just past a light blue/gray color. If you want lower hardness, temper at 700F. For Higher hardness, temper at 500F. A second temper at the same or slightly higher is advised to improve toughness. Be advised that water quenching a water hardening steel with a very thin cross section might crack it. I have hardened thin W1 blades by using compressed air or even oil very successfully.

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Haha, I had the same problem looking for super 8, that's what the other smith called it. But the point is the tempering process doesn't differ significantly from other steels, which is exactly the information I was looking for. I had no idea you could cool steel fast enough with air to harden it, fascinating bit of information. Thank you for the help!

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I have a book, "Bethlehem Tool Steels" copy right 1948, listing HW8 -Hot Work 8 tool steel

Typical Analysis
C 0.60
Chromium 3.60
Moly 8.50
Vanadium 1.75

They list heat treatment,uses, instructions for working, tempering tables etc. a couple of pages on this steel.

Also listed "Solid Drill Steel"
C .75, Manganese .20 Silicon .15
Uses- chisels, concrete-buster points, crow bars, blacksmithing tools, etc.

I don't have a scanner, but if you'd like specific info I can relay it.

Edited by markb
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your best bet is to chop a bit off and try various heat treatments out before doing your blade. see if it air hardens from non-magnetic, if not then try oil, then water until you get it hard (run a file across a few times just incase the surface has not hardened but the inside has).

When it comes to tempering start low, say 150C (sorry I'm european ;) ) and up it by 10C intervals using the 'brass rod test' in between.

junk yard steel is always fun :D

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If the chemistry Markb posted is what you have, it is air hardening. It will also need a much higher and longer temperature to get into a useful range. That is an M1 high speed steel with a LOT of molybdenum and that will not temper easily. 4 hours at 1075F will get you a Rc of 62. Technically, this is harder than woodpecker lips.

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I gave it to the son of a friend, so don't have it to measure, but overall length was about 4 inches. The nail is a 16d nail, which is the biggest I have found locally. Masonry nails are meant to be driven into concrete block, so are pretty hard/tough. I've been told they are made from 1095, though I have not been able to confirm this. I do know they have enough carbon to harden/temper. I have made several of these knives and a couple flint strikers. Someone has talked me out of every one of them! I've been meaning to make me another one...just the right size for pocket carry. Here's another view. Glad you likeed it...bart

Edited by wolfshieldrx
Another picture.
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