I live in the Austin Tx area and would love to meet up with an experienced knife maker. Over the last week I formed my first knife using the stock removal method. I have been reading quite a bit on the subject and am happy with what I fashioned. I'm attempting to harden the metal and have made several attempts bringing the metal up to non magnetic and quenching in vegetable oil. I'm testing the hardness with a file but I'm just not sure if it has worked. Its possible this type of metal just doesn't harden to the level I'm thinking it should. Someone who could take a look would be very appreciated.
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trying to harden 5160
- Thread starter sethg10
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- Jan 9, 2011
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Hi and welcome to Bladeforums!
5160 is very forgiving to heat treat but does need a 5 minute soak at 1525 or so to really get the best performance. You may be under temp as the temp is more important than the soak time. There are a few variables but I'm thinking more temp/time.
If you can send it off to be hardened you may wind up with a very nice knife.
---> Be sure to grind the knife back some before testing, it will have a soft outer skin known as "decarb" that needs to be ground off. Each heat cycle creates more decarburization so you may need to grind a bit. Once the knife is cleaned up a used file should skate off of the steel. (always get the knife right into temper and test later)
5160 is very forgiving to heat treat but does need a 5 minute soak at 1525 or so to really get the best performance. You may be under temp as the temp is more important than the soak time. There are a few variables but I'm thinking more temp/time.
If you can send it off to be hardened you may wind up with a very nice knife.
---> Be sure to grind the knife back some before testing, it will have a soft outer skin known as "decarb" that needs to be ground off. Each heat cycle creates more decarburization so you may need to grind a bit. Once the knife is cleaned up a used file should skate off of the steel. (always get the knife right into temper and test later)
Thank you guys for the replies. I am heating the oil to 130. My heating method is a torch and pipe to retain the heat. I know it's not optimal. I can try heating for longer. My fear is that I've been reading about overheating the metal and I'm not sure what the threshold is. When the blade is a dull red it is magnetic. Brighter red and its not. How thick is the soft layer? The outside of the blade turned black and developed some scale. Do I need to remove more than the scale? I'm going to try a longer soak. Thanks again for the replies.
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If your using mystery steel your wasting your time
Buy some 11sec Quick quench oil from McMastercarr it is cheaper and works with repeatable results
Edge quench if at all possible
Bring it to temp and be CERTAIN when you quench to move the blade in a cutting stroke for 5-6secs If you just dip it you get a Vapor jacket = It won't harden
Keep a large pan/container of hot water next to the quench tank after the 5-6 sec mark do a quick dip in the water then back in the quench tank moving until pretty cool
Let it come to room temp in the oil
Temper 375-400 deg 2hrs, 1hr left to come to room temp temper again 2hrs
Bring to room temp Clean off the crud and throw it in your freezer for 12-24 hrs or do a subzero Dry Ice/ acetone bath till the dry ice evaps in a regular cooler
Soak in hot regular Vinegar will take the crud off. Remember if your getting a bunch of De-carb your blade is too hot
Tip = keep the acetone in your freezer until ready to use this will add 1-2 rc points and give an awesome edge on 5160
Have used this method for years and am able to take a flat ground, convexed edge 5160 blade and chop steel with little damage
Oh yeah there is a local company Texas Knifemakers supply who does or did HT on 5160 give em a call
Buy some 11sec Quick quench oil from McMastercarr it is cheaper and works with repeatable results
Edge quench if at all possible
Bring it to temp and be CERTAIN when you quench to move the blade in a cutting stroke for 5-6secs If you just dip it you get a Vapor jacket = It won't harden
Keep a large pan/container of hot water next to the quench tank after the 5-6 sec mark do a quick dip in the water then back in the quench tank moving until pretty cool
Let it come to room temp in the oil
Temper 375-400 deg 2hrs, 1hr left to come to room temp temper again 2hrs
Bring to room temp Clean off the crud and throw it in your freezer for 12-24 hrs or do a subzero Dry Ice/ acetone bath till the dry ice evaps in a regular cooler
Soak in hot regular Vinegar will take the crud off. Remember if your getting a bunch of De-carb your blade is too hot
Tip = keep the acetone in your freezer until ready to use this will add 1-2 rc points and give an awesome edge on 5160
Have used this method for years and am able to take a flat ground, convexed edge 5160 blade and chop steel with little damage
Oh yeah there is a local company Texas Knifemakers supply who does or did HT on 5160 give em a call
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Unless you went to a very specialized metal supply store;
they do not have any harden-able steel there, they do not know what 5160 is and they just sold you mild steel.
Try another little test piece, get it hotter than magnetic, quench in water
put it in a vise and hit it with a hammer.
It should snap like glass.
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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- 38,477
Count - The "snap like glass" test sounds good, but unless you already know how to tell one steel from another, it isn't going to help. Take a piece of mild steel from the hardware store, heat it bright red, and quench in water...... it will snap like glass if you put in vise and hit it with a hammer. You and I could tell something about the grain size and maybe how it snapped, but a novice would say, OK, that means is good steel....which it isn't.
Seth - I will go with your word as the steel being 5160 because you ordered it and they said that was what it is. No reason to have any doubt there unless there is more to the situation.
To heat 5160 with a torch, here are a few suggestions:
First - lets determine what torch you are using. If you just have a propane torch, it won't work. An A/O torch is what you will need. A rosebud tip will be your best choice.
Second - how to heat the blade - Loose the pipe. It just soaks up more of the heat that the blade needs. Take a few fire bricks ( preferably the soft ones) and stack them into an "L" shape. Set the blade in the "L" with the edge in the crotch. Heat directly with the torch using a large and neutral flame. Play the flame to evenly heat the blade. Check along the spine with a magnet as it gets red to determine when it tops being magnetic. You have to heat about 100°F hotter than non-magnetic, so you want to take it about a shade or two brighter than when the magnet stops sticking. Try and get the blade evenly colored and keep the heat at that shade for as long as possible. In practicality, a minute is about all you can do with a torch. When the color is even and the blade has soaked for one to five minutes, immediately quench in the 130°F canola oil.
Testing for hardening - After the quench, be gentle with the blade. If all went well it is very brittle. Let it cool in the oil, and then take a new file and run it down the edge like you were trying to file an edge on the blade. The file might bite a tad on the first stroke as it takes off any decarb, but the next couple strokes should screech and slide along like you were filing glass. If it still bites after four or five strokes, the HT didn't take. If it is singing and sliding off the edge, it did OK.
Tempering - Immediately after the file test, clean off the blade by gently washing with soap and water and place in the kitchen oven at 400°F. Bake for one hour and take out. Rinse off in running tap water until cool, and place back in the oven for a second hour. After the second temper, cool off in water again and the blade is ready to finish by grinding/sanding.
Testing the edge - When you have a little experience, you may want to do what some more experienced makers do, and test the edge before finishing the knife. It pretty much requires a belt grinder to do this. Grind a quick thin edge on the blade at around 10° per side. No need to make it pretty or worry about getting it scary sharp. Take a piece of 1/4" brass rod and set it down on the workbench or table top ( epoxying it to a board is a good way to keep it from rolling around in the test). Put the knife's edge on the brass rod at 90° and push the blade sideways to try and deflect the edge a bit. You aren't trying to cut the brass rod in half or apply a lot of pressure and flex the edge heavily...just use enough pressure to make the edge deflect noticeably. Do this in a few places along the edge. Lift the knife and check the places on the edge where it flexed. (Be aware that every test spot may, or may not, have identical results. It is the average of the blade you are checking for.) If the edge flexed and stayed bent, the HT is bad or the temper is way too high ( most likely bad HT). If it chipped out, the HT is good, but the temper needs to be done one more time at about 25° higher and tested again to see if it will flex and not chip. If the edge flexed and returned pretty much to center, the HT was good and the temper is good..... dull the edge and finish the blade.
Seth - I will go with your word as the steel being 5160 because you ordered it and they said that was what it is. No reason to have any doubt there unless there is more to the situation.
To heat 5160 with a torch, here are a few suggestions:
First - lets determine what torch you are using. If you just have a propane torch, it won't work. An A/O torch is what you will need. A rosebud tip will be your best choice.
Second - how to heat the blade - Loose the pipe. It just soaks up more of the heat that the blade needs. Take a few fire bricks ( preferably the soft ones) and stack them into an "L" shape. Set the blade in the "L" with the edge in the crotch. Heat directly with the torch using a large and neutral flame. Play the flame to evenly heat the blade. Check along the spine with a magnet as it gets red to determine when it tops being magnetic. You have to heat about 100°F hotter than non-magnetic, so you want to take it about a shade or two brighter than when the magnet stops sticking. Try and get the blade evenly colored and keep the heat at that shade for as long as possible. In practicality, a minute is about all you can do with a torch. When the color is even and the blade has soaked for one to five minutes, immediately quench in the 130°F canola oil.
Testing for hardening - After the quench, be gentle with the blade. If all went well it is very brittle. Let it cool in the oil, and then take a new file and run it down the edge like you were trying to file an edge on the blade. The file might bite a tad on the first stroke as it takes off any decarb, but the next couple strokes should screech and slide along like you were filing glass. If it still bites after four or five strokes, the HT didn't take. If it is singing and sliding off the edge, it did OK.
Tempering - Immediately after the file test, clean off the blade by gently washing with soap and water and place in the kitchen oven at 400°F. Bake for one hour and take out. Rinse off in running tap water until cool, and place back in the oven for a second hour. After the second temper, cool off in water again and the blade is ready to finish by grinding/sanding.
Testing the edge - When you have a little experience, you may want to do what some more experienced makers do, and test the edge before finishing the knife. It pretty much requires a belt grinder to do this. Grind a quick thin edge on the blade at around 10° per side. No need to make it pretty or worry about getting it scary sharp. Take a piece of 1/4" brass rod and set it down on the workbench or table top ( epoxying it to a board is a good way to keep it from rolling around in the test). Put the knife's edge on the brass rod at 90° and push the blade sideways to try and deflect the edge a bit. You aren't trying to cut the brass rod in half or apply a lot of pressure and flex the edge heavily...just use enough pressure to make the edge deflect noticeably. Do this in a few places along the edge. Lift the knife and check the places on the edge where it flexed. (Be aware that every test spot may, or may not, have identical results. It is the average of the blade you are checking for.) If the edge flexed and stayed bent, the HT is bad or the temper is way too high ( most likely bad HT). If it chipped out, the HT is good, but the temper needs to be done one more time at about 25° higher and tested again to see if it will flex and not chip. If the edge flexed and returned pretty much to center, the HT was good and the temper is good..... dull the edge and finish the blade.