Question about pre-HT finish on 1084.

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redd1981

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Oct 4, 2011
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Hey guys quick question.

How important is it to get EVERY scratch out of the bevels before HT?

The reason I ask is because I usually leave them fairly thick and have to grind them again anyway so are 120 grit scratches enough to warp the blade to one side or the other during quench?

BTW I have always gotten 95-99% of scratches out of the entire knife with 220 before and have never had any issue with warping so Im not asking to be lazy,Just wondering if I could cut down some time since they will have to be ground again anyway.

Thanks guys.
 
This is just me, but I try to get them about perfect pre-HT. When I get them back I don't have to touch the grinder, just sandpaper and block and should be ready for handles and edge. Trying to sand out post-HT is much harder than pre-HT. Yeah you are going to have scale, but it comes off easy.

If you plan to hit the grinder post-HT on the bevels, at least make sure the flats are nice and smooth pre-HT.

I'll also add that I have a professional company do my HT and haven't had any issues with warping.
 
Thanks for the reply hawk. from my understanding with simple carbon steels like 1084 you need to be just under dimes width on the edge before HT (oil quench) especially for a back yard HT. and thats the way I have always done it before. as stated I have always gotten them almost perfect before HT in the past because I understand its easier to sand fully annealed. Just wondering if the parts that get ground again anyway can stand to keep the 120 grit scratches.

Just for clarity I am using Aldos 1084 heated in a propane paint can forge quenched in 130 deg canola oil.
 
If you are going to grind again to get out 120 grit scratches, you'll probably use a 220 or higher grit, so just make sure the amount you plan to take off leaves you with edge thickness you want before you put your secondary bevel or edge. If you are talking flats, yeah, you can leave those and just let the belt clean them up.

Hope that answered your question, if not I may have to wait till the AM since my brain my be on the fritz.
 
Ok I know sometimes Im not very good at asking questions the correct way on forums, so let me try not to be so vague.

my method of grinding is starting with a 60 grit blaze and cleaning it up with a 120 grit gator. After that I have always finished with hand sanding the entire blade with 220 redline rhynowet.

I guess what Im asking is if I sanded everything BUT the bevels to a uniform 220,could I leave the bevels at 120 since I will be going over them again with a 120 grit belt anyway. Is 120 deep enough to cause warping?
 
Belt grit shouldn't cause warping (unless this is something I'm completely unaware of). Warping is caused by going too thin in an area of the knife and your HT/cooling process.
You could do the whole knife at 60 grit and your chance of warping would be no different than if you did the same at 1200 grit. If you get the edge too thin you may get waving at the edge, or if you don't leave enough material in the handle, you could get warping. Precision HT'ing can help minimize this as well. Doing the backyard HT is going to bring in more variables.
 
I've only been working with carbon (1084/1095) till I feel the quality I'm putting out will demand the price to cover the higher end materials. That being said, I just love working with carbon and the character it has as it wears a patina. I'm a big fan of a knife looking "broke in" even if it is new. I do plan on using some next batch of steel I order for some friction folders.. probably 154CM.
 
I think the fineness of finish might be more important on oil hardening steels, I think excessively coarse finishes give too many places for cracks to start during the shock of the quench. Plus coarse finish > more surface area > more decarb to get through, but not sure that is a hard fact, just a suspicion.

On air hardening in a reducing environment (foil pouch), it doesn't seem to be all that important. I like to finalize geometry post HT, so I don't go too crazy with a fine finish beforehand.
 
First, a dime is about .050"...that is really thick for most blades. About half the thickness of a dime is what you want....025-.030".

Unless you will be grinding the bevels post-HT, take the entire blade to 400 grit pre-HT for simple carbon steels. Go even finer for any blade that will be at a high hardness ( 60 and above), or is a particularly tough steel (3V, M4). Take the edge to .015-.020 for stainless and finish to a perfect 400 grit surface or higher.
 
First, a dime is about .050"...that is really thick for most blades. About half the thickness of a dime is what you want....025-.030".

Unless you will be grinding the bevels post-HT, take the entire blade to 400 grit pre-HT for simple carbon steels. Go even finer for any blade that will be at a high hardness ( 60 and above), or is a particularly tough steel (3V, M4). Take the edge to .015-.020 for stainless and finish to a perfect 400 grit surface or higher.
 
Redd, I hear ya. Like was said, the scratch pattern is not going to affect the blade bending. A coarse scratch pattern is a good way to ask for a crack to happen during the quench. There was one knife in W2 that I had finished at 120 grit. I had always gone to 220, but because I grind a bit after heat treat to bring the edge down to about .007", I wanted to cut corners and stop at 120 grit. The 120 grit scratch pattern was up and down, instead of the proper lengthwise, and sure enough the steel cracked from the edge up into the blade about a quarter of the way up. Ever since then, I go to minimum 220 grit, and the scratches run lengthwise. Is it necessary to get EVERY scratch out when you go from 120 to 220? It may not be necessary to technically get EVERY single one, but you certainly want to make sure the edge and the area immediately behind the edge is cleaned up. And if you don't get every scratch pre-heat treat....then it is just going to be that much more difficult post heat treat.

Short answer.....go to 220 grit lengthwise and get every single 120 grit finish scratches erased. Leave at least .020" at the edge, and once hardened, go back to 120 grit and bring the edge down to where you want it. I like thin slicing type blades....so I go below .010"....usually between .005" and .007". It is a sort of agony having to go back over the 220 finish with 120 grit to cut the edge down, but it is what it is!

Don't do what I just did.....using Aldo's Blue Steel, I made a chef's knife. In order to minimize the amount of work I was going to have to do post heat treat to sand the edge down thinner, I thought I would go ahead and grind it as thin as I dare before heat treating. It was about .010". TOO THIN!!!!! I had a small area of the edge "bacon" on me, due to me grinding it too thin. Just don't do that! Thanks to Stacy, the REAL most interesting man in the world, I was able to fix that boo boo. Do NOT go below .020" for oil hardening steels! I know .015" will work....but that is the ultimate bottom line....it seems.
 
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