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First farriers rasp knife


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Velegski; transformation from austenite to martensite is usually a hardening step not a tempering step; however may I commend to your attention "cryo quenching" used to get retained austenite to transform to martensite---necessitating another tempering cycle afterwards of course!  It, of course, is most useful for alloys that tend to retain a lot of austenite after more "normal" quenching.

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Mr. Powers. Thanks,  as I've stated earlier I'm still trying to wrap my head around the heat treat, temper process. Funny that you mentioned Cryo. I know of the process but never attempted it. And cold treatments are the next chapter in a book by Dr. Thomas. Thanks

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This was posted by Steve sells in the heat treating knives and blades forum under the sub forum introduction to heat treating. 

          

(Tempering relaxes the thermal shock we caused during the hardening process, all hardened blade should at least get a hour or more to relieve the stress. Most take only 320F or so, and I prefer 350F two times at two hours each, with a rest period of one day between. When we harden the blade, there may be retained austenite, rather a small amount of the austenite that has not yet converted to martensite. This will convert into martensite after some time as room temperature or lower, and that is the reason for a second temper cycle, to relieve that also. This is also one reason many use a sub zero quench, for advanced steel treatment, to force the change into martensite.)

This is why I asked the question about retained austenite and the need to wait between tempering cycles. 

Pnut

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Still waiting for the thermometer but already thinking about the next steps.

I want to try an etch with orange juice. I know the patina won't last forever but I want to make my own long term testing with normal kitchen use. The question is can I do the etch before I epoxy the scales? Or does the etching has a negative influence on the bonding of the epoxy?

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With damascus I have not had any issues with the epoxy not bonding well after etching. Just clean the steel well with acetone or some other streak free cleaner before you glue it up. If anything I would think the rougher surface caused by etching would make the bond stronger rather than weaker, but I'm not going to say that with any certainty. 

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Hi Frazer, hi Thomas,

Tank you for your replies. Yes i heard of of such primers but more for painting wood/concrete. I'm new to metal working. My only practical experience is a two week basic metal working class bevor studies. So please excuse if some questions are very basic.

 

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Hi,

the thermometer arrived and I put it in the oven to check the temperatures during Christmas cooking. All temperatures were about 5-10 K lower than the dialed temperature. I think I used a wrong operation mode when I tempered the blade. I don't know the Englisch expression for it but there is a fan running in the oven to move the air in the oven. Thought it would result in a more even heat distribution but it didn't. Next time I use another mode for the tempering.

Also worked on knife #2 witch is made out of the left over part of the farriers rasp. But this brought me to hospital this morning. I had a respirator and eye protection glasses on while working the profile with the angle grinder but somehow a metal fragment got in my eye. Kept me awake to nights... Luckily the doc could remove it without any big problems. 

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The metal fragment might have been in your eyebrow. I've had it happen before. It used to happen pretty frequently at the rubber refinery when I was compounding batches until I started wearing a bandana very low on my forehead. 

Pnut

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I've had a piece lodge in my hair and fall into my eye when I took off my PPE too.  I keep a disk drive magnet to pull stuff out if it's just riding on the surface.

Not often mentioned but; high quality tweezers, a lighted magnifier on a base, a magnifying cosmetic mirror, and the disk drive magnet are all part of a good metalworker's first aid "kit". (Not to mention crazy glue, silvadene, and an antibiotic ointment...)

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Hi,

I have the first aid kit ready. 

The tempering is done and the blade reached straw colour. With the right oven mode the temperature was pretty accurate. Unfortunately the blade bend like a banana. I will try to correct it in the vice using bolts and if that doesn't work I ordered some metal clamps to try the re-bend using coins and angle iron in a tempering cycle.

Also did some vegetable cutting to get a feeling of the knife profile. Due to the thick spine the knife won't be a perfect slicer. And without the scales it is a bit heavy towards the tip. Knife #2 I will file with a thinner spine and maybe try to achieve a distal taper. Have to figure out how to achieve such a low angle with my jig. Keeping the edge thickness around 1.5-2 mm. 

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Finished the sanding of knife #1 today. It's not perfect but ok. Next will be the scales and I'm looking forward on this. 

IMG_20201229_141626.thumb.jpg.4441d5678f40183e131316824bed1d68.jpg

Also worked on knife #2 and became impatient... Hand filing the bevels take hours so I tried the 3x20 belt grinder again. Its not made for knifes but it removes metal faster than hand filing. And I learned that I have to work with a guide for the plunge lines. It takes just one moment and a crisp line is gone... 

Got an old 3 HP motor and I want to build a very basic 2x72 belt grinder. Nothing fancy just enough to speed up the bevel grinding. 

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