Did I ruin the HT

[Varga Knives]

Hey guys,

I had my first 6 blades heat treated by Darrin and I think they came out great (5-1084 and 1-1095). When finishing them on the grinder I figured I could do a few passes on one and then rotate to the next blade so as to keep them cool and not dip in water. I was wearing gloves and really didn't notice until a couple of hours in that they were still too hot to touch when the next rotation came around. Also, I blued two areas when hitting just the edge of the belt. I ground the discolored areas off quite easily but I dunno. Do you think they are all ruined? Is there a test I can do? I filed a notch in one and it wasn't easy so I know they are still hard but, i was able to file it. Does that say something? I really can't spend the money to send these out again right now so I would hate to just assume they are ruined.

Thanks!

 

[David Stifle]

It sounds like you got them really hot. If they were too hot to touch even after you did a roatation you may have reached a temp which softened the blades some. The areas which turned blue did get too hot, for sure. I would take the blade you think got the hardest and finish it up, put an edge on it, and perform cutting tests, paper, rope, etc. This should tell you how good the blade is. Good luck.

 

[Fred.Rowe]

Its best not to wear gloves when grinding hardened steel. Your bare fingers keep you posted on how hot the blade is getting as you grind. Bare fingers don't care much for 250 fh, time to put it in water.

 

[Cody Hofsommer]

The ones that had blue on them were too hot. If you didn't see any color they should be fine.

 

[Nathan the Machinist]

If you got areas of the edge blue you overheated it. Grinding the colors off won't change that. The overheating is worse in the thinnest part of the edge, but frequently the damage goes so far up toward the spine that no amount of "grinding it back" will fix it.

This is a good application for 'the brass rod test". I know we poo-poo this test around here because it is too subjective and largely geometry dependent, but I believe it will allow you to see areas of an edge that got soft if you'll keep a sharp eye and leave off the rose colored glasses.

If you take a sharpened blade to a nice thin sharp edge and then hold that edge against a brass rod and press it sideways into the rod hard enough that you can see the edge deflect you can run that blade up and down that rod. That edge will just flex and roll right over that rod. Areas of the edge where you ruined the temper will become bent.

Then you can cut up cardboard and soft areas will dull faster and show up under close examination with a flashlight.

Chop and whittle on a little hardwood, soft areas will roll.

If these blades are for yourself, friends and family I'd test them and use the good ones. I wouldn't sell these unless they were re heat treated.

 

[Varga Knives]

My guess is that the HT is ruined and I would hate to finish these all up and have them be less than optimal.

The wife is already less than enthused on how much I am spending on this venture so breaking the news to her that I need to "respend" money won't go over big but if it's what I need to do then so be it. Lesson learned.

The good news is that I tried sharpening one on the grinder for the first time and achieved good results real quick. I never sharpened an initial edge before so I had a lot of trepidation but it was easy. After all the hours spent working on these I was finally able to cut something and what a great feeling it was. I literally was laughing out loud in the garage with pieces of cardboard boxes flying all around me. This is my first experience with using something I have made and it adds another level to what I love about this hobby.

I have no plans to sell any of these but, like I said, I hate to settle for less than optimal so even if they are just gifts I think they should be right.

I have to run out now and buy a brass rod to do some testing.

Thanks!

 

[Varga Knives]

Ha ha. Jokes on me. So, like I said I sharpened one up and did the brass rod test but I could get no deflection. Presumably my edge was too thick. I decided to finish the rest to go back to HT without regard to over heating them. I was going to knock the edge back on the one I sharpened and do the same with finishing but, since this is the first one I ever sharpened I figured I'd have some fun first. I cut up a bunch more cardboard, then chopped an old axe handle in half (mind you this was not a chopper but only a five inch blade). I then whittled the axe handle to a point and went back to cutting a bunch more cardboard. After that I cut some paper and it sliced through with ease. It even whittled little curly q's. I looked at the edge under a loop and could see no damage. The only thing I could see was an area a few millimeters long where there is a little flat at the very edge. Barely noticeable except for the reflection.

I should have done as the advice suggested and then I would have moved on to sharpen the next one and so on. I still wouldn't know for sure if they are optimal but I really don't know how much better it could get. I don't think I had another knife that would stand up as well.

Needless to say I am going to have to send the others back but I'm definitely going to keep this one a put a handle on it.

So I'm a huge fan of Darrin Sander's heat treating and also of 1084. People who thumb their noses at 1084 be damned!

 

[Josh Mason]

1084 is a great steel. Does everything I ask of it. Darrin is also a hell of a guy. I'm more than impressed with everything he does.

I overheated a piece of a-2 awhile back. It got a bit of straw/green/blue color near the ricasso. I knew it was toast. After much testing and sharpening the discolored area dished out really bad while the rest of the blade was straight and sharp.

Take the gloves off, use sharp new belts (Blaze) and keep the bucket handy. As soon as you feel it get WARM is a good time to put it in the water bucket. Use some dish washing soap in your water to keep the flash rust off your 10xx carbon.