First knife: Edge thickness prior to heat treat?

S

SkunkWerX

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Jul 27, 2006
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Almighty knowledgeable knife makers,

I'm stumbling around in the dark, making my first knife using 5160 steel.
I am aware that I need to get all major work and finish done, before heat treating, and am working on it.
pics here: http://www.bladeforums.com/forums/showthread.php?t=456308

The Question: How thick or thin of an edge do you grind to, before heat treating?
If it's too thin (ie; sharpened) heat treat will crack or warp it, right?
That's what I am being lead to believe. :confused:

If it turns out decent, I'll send it out for heat treat, if not, I'll do a torch or hot coal number on it, and chalk it up to training. :o

Any other info regarding work to be done prior to heat treat is certainly welcomed.

thanks, in advance.

JL
 
I can only respond with what works for me. I use a lot of O-1 and do my HT with a Oxy. - Act. torch and grind to .020" thick at the edge. I flat grind, but when I do a hollow grind I leave the edge at least .025"- .030" thick. Many folks leave the edge much thicker, but like I said this works well for me. One thing to be cautious of, is be sure and use a neutral flame. If too much oxygen is involved you will see a lot of decarb. Also use a magnet to judge temp., it works very well. I temper in a convection oven twice at 380 deg. F for one hour each time. It yields a blade that checks out right at 59 RC but I always call out my Ht #'s as 58-60 RC. Again, this is what works for me. I almost forgot to mention that, I always remove all of the vertical lines before HT, as this seems to really help cut down on time when your doing the finishing touches.


I hope this helps
Nick:)
 
I am also just learning and had been uncertain as to thickness at edge. I sent my first one out for heat treat and was told it was way too thick. After talking about it over the phone, .020 at the edge was what I was also told.

I'm now trying to get it thinner but it's taking a loooong time.

Richard
 
NWA said:
I can only respond with what works for me. I use a lot of O-1 and do my HT with a Oxy. - Act. torch and grind to .020" thick at the edge. I flat grind, but when I do a hollow grind I leave the edge at least .025"- .030" thick. Many folks leave the edge much thicker, but like I said this works well for me. One thing to be cautious of, is be sure and use a neutral flame. If too much oxygen is involved you will see a lot of decarb. Also use a magnet to judge temp., it works very well. I temper in a convection oven twice at 380 deg. F for one hour each time. It yields a blade that checks out right at 59 RC but I always call out my Ht #'s as 58-60 RC. Again, this is what works for me. I almost forgot to mention that, I always remove all of the vertical lines before HT, as this seems to really help cut down on time when your doing the finishing touches.


I hope this helps
Nick:)
Click to expand...

NWA,

Hope it helps?? Man that is like GOLD. thanks much.

.020 is pretty thin, at least compared to what I have now.
I have dial calipers so I can dial it in.

That was a lot of help!

Thanks.
 
I stand to be corrected, but this is what I have gathered through reading responses to several threads on this subject:

I believe the thickness will be dependent upon which type of steel you are using . . . liquid quench, or air quench.

Liquid quenched steels will leave more scale/decarb and will need a little more grinding to clean up.

Air quenched steels, if properly sealed in foil, will leave little cleanup work and can almost be ground to a finished edge before heat treating.

I'd suggest contacting whoever you plan to use for heat treating, and ask them what they recommend.

Mike L.
 
.020 scares me with a paragon. I get a little carried away at times when
I'm grinding when things are going good. Lost one last week that measured .043 (440c) it left a nice ?? so bad I dont know what to call it in the blade. I intentionally broke it to take a look.
Just another learning experience.
good luck
 
I think the answer depends on what grit you are going up to prior to heat treat and you comfort level and experience. If you go up to 220 or 400 grit then you can leave the edge pretty thin, because you really don't have much further to go after heat treat and the steel is much harder then too. But if you only go to 60 grit then you will want to leave it a little thicker because you still have some steel to remove. Also if you polish the blade remember that the buffing compound also takes away steel and it can give you a real thin edge if you don't pay attention. I know, because I've done it. I think the most important thing to remember is "Once you've taken the steel off, you can't put it back on!" My $0.02.
 
Make sure you take enough off before ANd after your HT. I have done a few where I left the edge too thick after HT and couldn't figure out why it wouldn't get sharp, in some cases, ater sadning and sharpening some more. I did that recently on a fighter and thought I had screwed up the HT. I went back to the grinder after the knifewas put togther and whacked down the edge a bit more (convex edge) sanded it it and now it is good to go:D .020-.030 looks quite thin to the normal eyeball. Trust your calipers.
 
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