Justin Presson
Well-Known Member
Great WIP man. Your explanation of grinding was good that is how I do it to.
Pairing knife WIP
- Thread starter TDPurcell
- Start date
I appreciate the postive comments and feedback.
My heat treatment recipe for 440c stainless steel comes from the Admiral Steel website:
http://www.admiralsteel.com/reference/sstltech.html
It calls for HT of 440c as follows:
Initial Quench Temperature - 1850°F-1950°F max
Hold for 30-45 minutes
Quench in warm oil or air cool
Do not overheat (too much time or too high temperature)
Hardening & Tempering Information
300°F - 1 hour - R/C 60
500°F - 1 hour - R/C 57
800°F - 1 hour - R/C 56
I've found similar information on other websites.
I'm making kitchen knives which are thin to begin with, and I've ground two of my blades pretty thin with higher grits, so I've decided to go with 1850 degrees for 25 minutes as my hardening time and temp. I placed the blades and the three coupons, wraped in tool wrap, inside the room temperature oven and set the oven to ramp up to 1850 as fast as it can and hold it for 25 minutes. It took the oven about 35 minutes to go from 73 degrees to 1850.
One thing I haven't done yet with HT is preheat the blades at a lower temp and hold for a while prior to ramping them up to the max. temp. I'll try that in the future to see what happens as I've read that several HT specialists do it that way.
I currently do not have aluminum plates for quenching, so I air quench in front of a fan. (pics below).
Tracy Mickley's video is very informative on the steps for heat treating stainless steel.
http://knifedogs.com/showthread.php...less-tool-wrap-plate-quench-cryo-video-54mins
My heat treatment recipe for 440c stainless steel comes from the Admiral Steel website:
http://www.admiralsteel.com/reference/sstltech.html
It calls for HT of 440c as follows:
Initial Quench Temperature - 1850°F-1950°F max
Hold for 30-45 minutes
Quench in warm oil or air cool
Do not overheat (too much time or too high temperature)
Hardening & Tempering Information
300°F - 1 hour - R/C 60
500°F - 1 hour - R/C 57
800°F - 1 hour - R/C 56
I've found similar information on other websites.
I'm making kitchen knives which are thin to begin with, and I've ground two of my blades pretty thin with higher grits, so I've decided to go with 1850 degrees for 25 minutes as my hardening time and temp. I placed the blades and the three coupons, wraped in tool wrap, inside the room temperature oven and set the oven to ramp up to 1850 as fast as it can and hold it for 25 minutes. It took the oven about 35 minutes to go from 73 degrees to 1850.
One thing I haven't done yet with HT is preheat the blades at a lower temp and hold for a while prior to ramping them up to the max. temp. I'll try that in the future to see what happens as I've read that several HT specialists do it that way.
I currently do not have aluminum plates for quenching, so I air quench in front of a fan. (pics below).
Tracy Mickley's video is very informative on the steps for heat treating stainless steel.
http://knifedogs.com/showthread.php...less-tool-wrap-plate-quench-cryo-video-54mins
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The first two pics show the blades and the tool wrap. Sorry for the blood. This stuff is razor sharp and doesn't work as easily as aluminum foil. I usually end up cutting a finger or two, but it's nothing serious. The tool wrap keeps oxygen away from the steel during the HT. You can see in the first pic that I also put a piece of paper in the pouch. This is supposed to burn off any remaning oxygen inside the pouch. I'm not sure if it works, but it might, is easy to do, and certainly doesn't hurt anything.
The second pic shows the sealed pouch. Watch Mickley's video linked above and see him construct a similar pouch.
The third pic is my HT oven, another craigslist purchase, and the final pic here is the pouch placed inside the room temp oven.
The second pic shows the sealed pouch. Watch Mickley's video linked above and see him construct a similar pouch.
The third pic is my HT oven, another craigslist purchase, and the final pic here is the pouch placed inside the room temp oven.
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These next pics are of me taking the knives out of the oven after they had soaked at 1850 degrees for 25 minutes. Nothing to say here except you'll notice that there is a glass cutting board that is in front of the oven. I hadn't noticed it. Long after I had taken the knives out and after they had cooled off to room temperature, I had the oven door open for the oven to cool off. That glass cutting board spontaneously shattered into a thousand pieces. I knew better, but I wasn't thinking about it being there so I didn't really notice it. Anyway, no one was hurt by my foolish mistake, so lesson learned.
When I dumped the blades out, you can see the coupons falling out of the packet as well.
You can also see that the blades are cooling down pretty quickly. I have a fan just off to the right of the picture that is blowing air on the blades. Final pic shows the blades on the cooling on a rack and the fan.
When I dumped the blades out, you can see the coupons falling out of the packet as well.
You can also see that the blades are cooling down pretty quickly. I have a fan just off to the right of the picture that is blowing air on the blades. Final pic shows the blades on the cooling on a rack and the fan.
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The next pic shows the HT patina left on the blanks. It doesn't look too bad and should clean up pretty easily.
The next two pics shows the results of the different grit finishes (600 and 2000). I was afraid of getting too thin on the finer grit finishes, and I lost the tips on those two knives. I'll not take a knife that thin prior to HT again. You can see in the third pic that the two knives with the lesser grit finishes (240 and 400) maintained their tip. I think a 600 grit finish prior to HT might be fine as long as the tip is not thinned too much. I've heard of other people that leave a thicker tab at the tip of their thinner knives prior to HT, and I might try that next time as well.
Regardless, I think the two knives that lost their tips can still be reshaped into decent paring knives.
Next up....hardness testing after the intial hardening and before tempering.
The next two pics shows the results of the different grit finishes (600 and 2000). I was afraid of getting too thin on the finer grit finishes, and I lost the tips on those two knives. I'll not take a knife that thin prior to HT again. You can see in the third pic that the two knives with the lesser grit finishes (240 and 400) maintained their tip. I think a 600 grit finish prior to HT might be fine as long as the tip is not thinned too much. I've heard of other people that leave a thicker tab at the tip of their thinner knives prior to HT, and I might try that next time as well.
Regardless, I think the two knives that lost their tips can still be reshaped into decent paring knives.
Next up....hardness testing after the intial hardening and before tempering.
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The next pics are of my hardness tester. This tester (craigslist again) only does a superficial hardness test. It can be set to several differnt scales, but I'll be using the 45N scale which can then be converted to the C scale using an app I have on my phone. The tester has a diamond indenter, and my understanding is that with superficial hardness testing, the indenter does not penetrate as far as a C-scale test.
The first thing I did was check the calibration with a test block that should read 52.1 (+ or - 1) on the 45N scale. I ran a test on the block three times and came out with 51.2, 52.0, and 51.5, so it appears that the tester is dialed in fairly well.
The first thing I did was check the calibration with a test block that should read 52.1 (+ or - 1) on the 45N scale. I ran a test on the block three times and came out with 51.2, 52.0, and 51.5, so it appears that the tester is dialed in fairly well.
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I performed five hardness tests on the coupons and got the following results (45N Scale):
67.1
66.0
68.1
68.0
66.5
This averages to a 67.14 on the 45N Scale which converts to 60.5 HRC according to my phone app. It appears, therefore, that my initial hardening was successful.
I'm going to temper the blades (and the two remaining coupons) two different ways. Batch 1: two 1-hour tempers at 400 degrees. Batch 2: two 2-hour tempers at 400 degrees. I'll let the pieces come to room temperature between each temper, and I'll test the coupons again after tempering is completed.
I'd be happy if anyone knowledgeable of metallurgy and/or heat treating stainless steel would comment about anything I might be doing wrong or could do different.
After tempering, its time to clean up the HT patina and finish the blades and handles.
67.1
66.0
68.1
68.0
66.5
This averages to a 67.14 on the 45N Scale which converts to 60.5 HRC according to my phone app. It appears, therefore, that my initial hardening was successful.
I'm going to temper the blades (and the two remaining coupons) two different ways. Batch 1: two 1-hour tempers at 400 degrees. Batch 2: two 2-hour tempers at 400 degrees. I'll let the pieces come to room temperature between each temper, and I'll test the coupons again after tempering is completed.
I'd be happy if anyone knowledgeable of metallurgy and/or heat treating stainless steel would comment about anything I might be doing wrong or could do different.
After tempering, its time to clean up the HT patina and finish the blades and handles.
Attachments
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