Quenching and magnets.

M

mpj13

Joined
Oct 5, 2001
Messages
108
I just finish my heat treat on my first knife (I think) one question about this phase. I put the blade in the fire and it seemed to take a while to heat up and changed colors, it seems to have gone non-mag but it was not red hot, when I put it in the oil it just smoked a little and thats it. I tried to heat and quench again, I waited until it got red hot and made sure that it was non-mag and then put in oil, this time a flame popped up all aound the area were the blade was submerged and it bubbled just a little and then sat there. I quess I was expecting fire works to go off or something. I used vegi oil. Does this sound right for it to flame up and then fizzle a little? Thank God I did not try it whith a propane tank, while making a fire was messy it was easy just to place it in the fire and check it every now and then.

My problem is I'm not totaly sure if I did it right. I tempered it at 345-400 for 1 hour each time and then I sanded it down som,e put a slightly sharp edge on it and tried the brass rod test. If I did the brass rod test right then I should be okay. I took the rod and layed it across the edge of my knife, like the form of a cross and then ran the knife down the brass rod maintaining the same cross patern. After doing this I checked the edge and it looked fine, no rolling or chipping. Did I do the test right?

One quick opinion. Do you guys like to use 1/8" thick scales of black micarta (Linen) for knife handles? After getting my order it looks like the 1/8" thick scales will look small as a knife handle. I also have 1/4" fiber handles.

Well if it sounds like the knife heat treat went good then I am on my way to make the handle and then finish this bad boy. Please if anyone could give a few quick glances and my questions it would help out a lot. I want to make sure I have a tough knife when I'm done. Thanks for your time reading this.
 
Thats pretty much all there is to it, you should keep turning the blade when heating to help it heat evenly on both sides and all the way though, but when it gets to non-magnetic quench, 1 thing is don't judge the quenching heat by color,always rely on what the magnet does. Color of heated steel doesn't show in sun light or other bright conditions until the temp gets way up there, so rely on that magnet.

As for the brass rod test, I always take a 1/4" rod about 8" long and tighten in down in a vise sticking out the side. Then holding the blade at approx.a 60 degree angle with a fair amount of down pressure drag the cutting edge across the rod. Check the cutting edge for any damage and then turn the blade over and run the other side.If it flexes and returns its gooooood,if it chips -still to hard, raise draw temp 25 degrees and draw again, if it doesn't return and stays rolled over -to soft, heat it up and reharden , then drop draw temp 50 degrees and draw and check again..

Hope this helps

Bill B.?????
 
Just to add a little something to bills answer for you.I always keep a new sharp file by the quench tank and after I quench the blade and it is cooled off I check the edge with the file.If it bites into the steel you missed the mark and need to try and re-harden.If the file scates along the edge and won't bite the steel then you have it hard and are ready to draw the temper on it.The oil will not always fire up when you heat the blade to non magnetic,I don't know why it doesn't but I have hardened several that didn't flash the oil and then the next one will,I may be just getting over the temp just enough to flash the oil,But it doesn't neccisarily have to Flash fire on you.That is why I use the file test,if I have any questions of myself like did I miss it the file will tell.
Bruce
 
One thing that I have never heard anybody mention is that some magnets will stop working when they get too hot. The first magnet I used was a small telescoping magnet that I had laying in my garage. After heat treating about 3 blades, they seemed to be reaching non magnetic way too fast, I checked the magnet, and it wasn't even a little bit magnetic anymore. I have done this too one other magnet, I think they were both just peices of steel that had been magnatized, kind of like magnetic screwdriver bits. SO now I took the magnet out of an old speaker, and that doesn't seem to be affected by heat.

Kyle Fuglesten
 
I mostly did go by the magnet, If I over heated the blade does that mean it is bad? It seems okay so far. When I tested it with the magnet I would check it on a non hot piece of metal to make sure it was working, so I think it was accurate. Do I need a really strong magnet?

I went back and did the brass rod test again, I help it on about a 60 degree angle and ran it down the rod. I could not see any visible damage, I put a LOT of pressure on it too, one thing that worries me is I could feel a little catch when I ran my finger nail down the blade.

The knife is sharp but not as sharp as I want to get it. Is the best thing to finish hand sanding it and then use a sharpening stone? I am thinking about buying a good sharpening kit. That along with a strip of leather should work. If I just use the stone and sand paper for now will this give a good sharp edge? Thanks a lot.
 
I can add a little bit about magnets, the shiny ones that look like steel are usually a blend of Alnico which is more susceptable to demagnitization by heat and vibration.

Ferrite magnets, usually brown, black, or grey and chip easily, often used in speakers, are more resistent to demagnitization.

Rare Earth types ( Samarium/cobalt, or Neobnyium/Iron ) are also shiny, usually coated by plating or paint, usually smaller, stronger and are also more resistant to demagnitization. They are also brittle like ferrites.

DaveH
 
You just need a good quality magnet, it doesn't have to be a big strong magnet, I believe mine was rated to lift something like 12 pounds,its a construction magnet and all I could find. You can get one at your local hardware store.Or like a lot of these guys an old speaker magnet works if you have one laying around. I've checked a lot of blades during heat treating with this magnet and it is not showing any signs of going bad, like Bruce said, your file will tell you if you didn't get it hard.

As for the brass rod test, if you put a lot of pressure on the blade when you pulled across the rod and all you got was one tiny chip I would say you are awfully close as to the correct draw temp.It might be just a touch hard but that should help it to hold an edge better, it depends on what you intend to use the knife for but I would leave it alone.

Finish the knife and then sharpen, safer that way, then a good stone to get the correct edge bevel and then drag it across some real fine sandpaper thats laying on something hard and flat, like a piece of glass, then polish it on your leather strap and watch the hair fly.

Hope this helps.

Bill B.????
 
Thanks a lot guys. I'll just leave the knife like it is as far as hardness and tempering go. Next step is making the handle. Since this is my first handle I am going to use a 1/4" piece of oak and some stain to add a little style to it.

This has really been a lot of fun, I already have two more knives in the plans. A push dager, mostly because I have 4" piece lefterover, and then a longer 12" knife. I am thinking about trying to make a tanto styled knife with a 1/8" black linen micarta handle. I am worried that I may be biting off more than I can chew, it seems like a Tanto will be difficult, but who cares I'll never learn until I make a few right?
 
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