Heat Treat Then Start the Grind?

O

otpowell

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Jun 26, 2013
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How many of you heat treat before starting to grind the blade? Us it better to grind some of the blade then heat treat? I do like the idea of grinding after heat treating so that you don't have to worry about the blade warping. Also, does everyone use an anti mill scale compound? Is that essential?
 
I'm by no means an expert, but if you grind after heat treating, and heat the edge up in the process, I'm pretty sure that messes up the heat treat. The way I understand it is forge/temper, grind, then heat treat the final product at a lesser heat, to make it less brittle.

Apparently Bark River sometimes gets flak for doing this, and there have been reports of chipping and such. Not trying to name drop specifically, nor do I have personal experience, which is why I say apparently. You can google it or use the BF search function.
 
This should probably be in the knife maker section. Most will tell you to start off with annealed steel and get 80-90% of your grind done. You want to leave the edge about as thick as a nickle to help prevent warping then you can finish everything after the HT being sure to keep the blade cool.
 
Grinding after HT is a great system....for an advanced maker. It requires good heat control, and preferably wet grinders.

Grinding before HT is the best option for almost all makers. Just make sure your blade is ready for HT with the right edge thickness, and make sure all stresses have been relieved before HT. Warp is a problem of something being amiss in preparation not in the actual HT.

I only grind thin fillet blades in Stainless post HT. They have a much higher cushion in the amount of heat they can build up before damaging the edge hardness than a carbon blade has.
Currently, I don't have a wet grinder set up in the shop. I have a 12" deep dip can hanging under the grinder on the front of the bench and grind, dip, grind, dip.
 
I have tried both methods. I am not an advanced maker by any stretch, but I realized pretty quick that my preference is to grind all of my bevels POST HT. For me, It is MUCH easier to control what I'm doing this way and produce better grinds. There are some cons to this approach I suppose. You will obviously go through belts a little quicker grinding hardened steel and you REALLY have to pay attention to not overheat the steel. I have adapted to this and it's not been a problem so far. I keep my dunking bucket very close when grinding. I make one pass and IMMEDIATELY dunk to cool. I've not had any issues so far overheating or exceeding the temper temps using this method.

Adam Buttry
 
What's the best method for bringing down the edge after heat treat? Specifically for begginers.
On my first couple of knives I did some hand sanded and then sharpened, but I didn't like the blade being so thick behind the edge and/or the secondary bevel being overly wide.
The last blade and the one I'm working on now I took back to the grinder after HT. I'm just working slow and dipping in cold water often. I keep my bare fingers on the backside of the blade to apply pressure and feel heat. When my fingers get hot I dip the blade.
I imagine that if the standard practice is to heat treat with a nickel width ~ 0.06, there has to be some grinding post heat treat to get down to a nice thin edge. Or am I just being impatient and should really be doing the final sanding by hand?
 
On 1/8 and thicker, I do my grinding before HT. Edge down to half a dime thick. Nickel thick is way too fat unless you're planning on doing some grinding after HT. I have started using some 3/32 stainless and grinding it after HT. One, it's thin, so it doesn't take much to grind it down, even hard. Two, it doesn't warp when you plate quench it, whereas a tapered tang, beveled 3/32 blade comes out of the plate quench like a snake. Three, it's stainless and so a bit less sensitive to overheating, as Stacy mentioned. I still dip it every pass.

Grinding after HT isn't for the craftsman 2x42 or single speed Grizzly guys, IMO. It takes control, attention to detail, and a slow grinder for it to be efficient.
 
I haven't tried it yet but I have been thinking about grinding post HT on some CPM 154 CM and not using the foil when heat treating. I hate that stuff and if your going to grind after HT why use it
 
I grind all my blades before heat-treatment. From what I've seen warp won't be an issue with blades 1/8" thick or over...

I generally take my edges to about 0.020" (0.5mm) before heat-treat.

I have been using an anti-scale compound called ATP-641 that you can get from brownells. That worked fine for me when I heat-treated O1 in a forge, but now that I'm heat-treating A2 in a kiln I'm constantly having issues with minor decarb. It's only superficial but it takes a bunch of work to sand it out to get a nice stain finish, for that reason I will be switching to doing my heat-treating in stainless foil instead.
 
Thanks all. I think I'm gonna grind to dime thickness, anneal to remove all the stress, then heat treat, then finish the grind.. Best way for a new knife maker?
 
otpowell said:
Thanks all. I think I'm gonna grind to dime thickness, anneal to remove all the stress, then heat treat, then finish the grind.. Best way for a new knife maker?
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I do all my grinding before heat-treat, it works fine and I think that's probably what I would recommend for a beginning maker too.
 
I found a lot of people talking about how far down they can take their blades before HT, but I've found it's just not worth it. I like to get down in the ballpark, but with hollow grinds, I usually have been going .030" or more. I've had more movement than I like when going under .025", and it just really doesn't take that long to dress them up after HT with good ceramic belts.

Maybe if I start doing more flat grinding, I will have a different level I go to for that, but I find that hollow grinds like to move around, especially high ones with a thinner lower section.

In reference to Jason Fry's comment above, I just lost a blade in S35VN, was a full hollow ground w/distal taper and tapered tang, w/edge at 0.020", came out completely unfixable.

I can't imagine the time saved in grinding a few extra thou before HT is worth the time lost when a blade warps just a tiny bit too much to grind out. Not only did I lose $30 in materials and HT, I lost almost an entire shop day in time, plus a knife that would have probably sold for $200+ if I'd been able to use it.



More on topic to the OP, I don't see any problem with grinding after HT. I usually leave quite a bit left to grind on mine, so that no matter what happens in HT, I can take care of it.

I spent a couple decades grinding pre-hardened tool steel blanks for machining, most often M4 which is one of the tougher ones. Just keep it cool by constant dips in water, use quality belts, and you'll have no problem.
 
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I do flat grind everything, not hollow. Maybe the thicker area behind the edge keeps the edge itself from warping?
 
Yeah, I think that's it.

I almost got myself into trouble on my earlier knives, because I started out doing hollow grinds, reading HT prep advice for flat grinds.

I'm anxious to get set up for flat grinding and see how the two behave in comparison to each other.

I think my final stop will be large radius hollow grinds, probably with platens, as I think that flat grinding makes more sense from an engineering standpoint, but I really like hollow grinds just because I guess. :)
 
Agreed that hollow grinds are more sensitive to warp, I hadn't thought about that as a factor in the discussion though, good catch!
 
aarongough said:
Agreed that hollow grinds are more sensitive to warp, I hadn't thought about that as a factor in the discussion though, good catch!
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Gough Customs! Wow I just got done watching some of your videos. Nice videos! You make it look simple and easy using hand tools. Do you have a belt grinder or do you stick to your files all the time?
 
I like to leave more steel on longer blades. Maybe about the width of a nickel. Then heat treat. They seem to warp more than shorter ones. On the smaller blades i will go to about .02. Another thing to watch out for is keeping everything even(plunge lines, distal taper, bevel, ect.) if you grind before heat treat. I used to just do everything rough and noticed i got more warp when everything wasn't ground evenly on both sides. By the way this is with carbon steels and doing the heat treat myself. ymmv. Bomp
 
I usualy grind the primary grind then when its around 1mm left before the apex if formed i heathreat and temper the blade before i finnish the grind, however if you are working with a verry thin grind you have to be verry cearefull of overheating the edge. if you happen to overheat the edge you have to be prepeared to re heathreat the blade in order to get rid of the weakend steel. if you are working with tool steels or exseptionaly hard steels like "Zdp189 and D2" i tend to grind them down to around 1/2mm - 1/4mm thick at the apex because if you heathreat tool steels or harder steels like "Zdp189" they will realy tear up your sanding belts, belts that are below 80girt tend to just get instantly striped.
 
otpowell said:
Gough Customs! Wow I just got done watching some of your videos. Nice videos! You make it look simple and easy using hand tools. Do you have a belt grinder or do you stick to your files all the time?
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Thanks! I have a grinder now, and use it for most of my work. I'll still likely go back to the filing jig from time to time when I'm demo'ing something for a video...
 
I only hollow grind and have lost a lot of blades to warp recently, going to thin .020 at edge before HT.
Going back to .030 to .050 and see how that works.
 
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