Reprofile a tool or knife of hardened Steel, fast, and without machines?

S

Sir Joe

Joined
May 30, 2015
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114
Hi guys!

Once again I must ask the experts.
I am a bit confused in this moment.

I had to reprofile a Roughneck Mini Mattock. It came with very very obtuse angle, and I wanted to make it MUCH thinner, so that it would cut roots much easier.

I had read that even with very coarse Waterstones or with a Spyderco Sharpmaker with CBN rods one needs half an hours to change the angle of a S110V Manix 2 knife (which is just 2,5mm thick), so I thought it would have been extremely slow (if possible at all) doing that with my Mini Mattock.
But I did not want to use a machine like a Flex or so, because of the risk that when the angle becomes thin enough the metal can become too hot and the Hardening gets lost.

So, I thought that a File could be a good idea.
I thought so, because a File has got much much coarser "grit" than a, for example, 120 Grit Diamond Sharpener.
I also thought that the only reason why Diamond and CBN and Ceramic and Silicium blabla sharpeners can bite a hardened steel, is because they are harder.
So I thought that if I could find a File which is harder enough than my hardened steel Tools, I could do the job with it.

So I have bought a File from Dick, a "famous" German producer.
It was written "specially for Steel".
Well, the File did not do the job, on a 8cr14mov 58HRC Sanrenmu VERY cheep blade.
So I did not even try it on the Mattock (where the material to file away is MUCH more).
Somebody then said to me, that it is NOT possible to file a hardened Steel, no matter which File you use and how hard it is.
It was also said to me that when one buys a File and he reads "specially for Steel" it is ALWAYS meant "normal not hardened Steel", because it is somehow a sort of convention in this field, that when one speaks of Tools and says "Steel" without specifying if hardened or not, then it ALWAYS means strictly "not hardened".
And for this reason, a File advertised as "special for Steel" it is always only for "not hardened Steel" and I should supposedly know it.

So, my questions would be:
1) is it true that it is internationally known that when one speaks of tools and Files and he says just "Steel" it is ALWAYS meant "not hardened steel"? Or would you under "special for Steel" also, like me, understand "for all Steels, hardened or not"?
2) can a File, if hard enough, bite a hardened Steel so to be used for reprofiling? If yes, which material should be the File made of, and how hard should it be? For example, I have seen Files of Vallorbe, called Valtitan, which are coated in Titan, and are 72HRC hard. I would use them on 58-62HRC hard Steel. Would that make sense?
3) IF I can use a File, and if my aim is to use it just to take as much material I can and than finishing the job with a CBN or Diamond or Ceramic sharpener, how fine/coarse should the "grit" of the File be? For example, I had understood that with a Diamond sharpener one must choose a coarser grit for reprofiling (something around 120 or 200). But I have read about Files that the harder a material is, so finer must the grit of the file be.
And I just can not understand this.
4) what would YOU use to make the reprofiling as fast as possible, if you would not have to use any machine? And why would you not use a file, not even for the first part of the job?
 
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DeadboxHero said:
DMT X coarse. My closest companion. From axes to knives.
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Hmmm.
I have something similar, a Lansky double sided, 120/600.
I think DMT X Coarse is less than 120. Right?
I think that DMT makes an XX Coarse which is 120.
So, are you talking of sharpening or of dramatically reprofiling?

I am talking of the second.
Imagine, 2cm thick blade, 5mm long (yeah, just a mini mattock). 45° or more.
I have to bring it to 30 at least.
This means, I have to go down 3mm, on each side, on heardened steel, in a surface of 1-2cm x 5cm.
Can you really do that with a DMT X Coarse?
If yes, I should be ok with the Lansky 120.
I thought it was just impossible.
Or, veeeeeeeeeeeeery slow.

(Still wanting to know about files, from who has experience with them.)
 
I'm with you on the extra coarse. Never owned an extra extra coarse but it is in my Christmas list. I basically reprofiled a s60v blade with it, took a while but it came out well. I am no artist but I was pleased with the final result.
Russ
 
get one of the coarse dmt stones/plates ,continuous surface and you shouldn't be disappointed. i use them on various woodworking cutting edges from o-1 to carbide and they never fail. that said their are some full size diamond files out there,dmt has a folder with a little something extra they call hardcoat that are supposed to be able to sharpen kitchen ceramic knives. woodpecker also has some diamond files in 100 and 300 grit ( or 140 and 50 microns respectively;more microns=more coarse,fewer microns=more fine. sorry if that was redundant ).
 
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I only use files on annealed steel or low HRC steels otherwise its not as effective as a diamond stone.


X coarse is 220
XX coarse is ~120
 
Try the file. I doubt your mattock is as hard as your knife blade, or close to the hardness of the file.
If the file cuts the steel, use it.
 
I'd go with Bill's advice. No....files are not made for hardened steel. Even corinox files, rated for stainless steel, are meant to be used on annealed steel only. They certainly are not "meant" to be used on hardened (58+) knife steel. However your mattock is likely mild carbon steel at low to mid 50s HRC. Take that file and go to town with it. With that said....abrasives are probably a better option if you're wanting to change the geometry of a mattock. Cheapo silicone carbide sharpening stones can remove A LOT of steel in a hurry!
 
i edited my post, but just in case: i was speaking of full size diamond files(which in essence the dmt folding sharpeners are). garret-wade sells some as well but off the top of my head i don't recall the grit/micron size. if you want a japanese alternative to dmt, lee valley carries atoma diamond plates with an overall flatness of +/- 0.04 mm. also there is some differences between monocrystalline and polycrystalline in terms of speed of sharpening and stone longevity. two of the m.power diamond files at woodpecker(and i'm sure other sites) have two handles,one on each end,so in use it can be similar to a spokeshave, or employed as a traditional file. hope some thing in all that helps. good luck
 
Hello everybody, thanks for the awesome answers.
I would not know anymore what to do without forums.

samuraistuart said:
I'd go with Bill's advice. No....files are not made for hardened steel. Even corinox files, rated for stainless steel, are meant to be used on annealed steel only. Cheapo silicone carbide sharpening stones can remove A LOT of steel in a hurry!
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I saw similar files, from Dick and from Vallorbe. They are Titan coated and 72HRC.
What do you think? Still not enough to bite on a 58-62HRC heat treated Steel?
They are sold as "able to file also materials before known as impossible to file, like hardener steel" and it is said that the teeth are not going to be damaged.
Now, marketing is marketing, but, I have asked around, maybe not the right people, some German Smiths. I say "Not the right people" because SMiths can de-hard and re-hard steel, so they would never get to the idea of filing hardened steel. If they really want to file it, they would de-harden it, file it, and re-harden it.
Whatever.
They told me that such a Titan Steel could bite in a hard steel, but for some reason related to the structure of steel the file should not have a coarse teeth, rather a fine one (I did not really understand why). So that finally a Diamond or a Stone would be faster.

I have taken the decision to believe these people. I will anyway, when I have money, buy a Titan File, to try it on my Mattock, and once I have it I will also try it on hardened steel.
But for what I understood there and here, I was worrying for nothing. Apparently Diamond and coarse stones are much faster than what I thought.
So, I have this Lansky The Puck, and I have a Lansky 120 Grit Diamond sharpener. I will also buy the very coarse sandstone which was suggested to me, it is cheap enough.
And I will experiment.
Later with more money I wish to buy the CBN rods of the Sharpmaker, and a some Titan Files (after all, I have no files).
I am convinced now that the best way to learn is to ask people, and then experiment yourself.

Bill DeShivs said:
Try the file. I doubt your mattock is as hard as your knife blade, or close to the hardness of the file.
If the file cuts the steel, use it.
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Yes I think you may be right.
Now I did it with a flex with abrasive paper disc. It worked. I burned a bit the tip.
What should I do if I see that the edge gets damaged easily now? saw a few mm away to eliminate the de-hardened part (IF it was hardened) and grind again with stone/diamond?

DeadboxHero said:
I only use files on annealed steel or low HRC steels otherwise its not as effective as a diamond stone.
X coarse is 220
XX coarse is ~120
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Apparently the Coarse of Lanskiy correspond to the extra extra coarse of DMT. My Lansky is 120/600.
I thought that a file, if hard enough, would be better than diamond for a fast regrinding, as I had in mind how well and fast they bite on iron. I suppose I did some maths wrong in my head.
DeadboxHero said:
A bench vice really helps adding more pressure to speed things up.

Also gloves for safety.
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I was expecting a video of somebody filing his hands due to not using gloves.
It was thrilling, watching that video thinking "oh no, now he will file his hands!".
Yes, I did this mistake too, I have used the file free hand and one hand. I should have fixed the tool/knife and filed with force and two hands.

neal70 said:
i edited my post, but just in case: i was speaking of full size diamond files
also there is some differences between monocrystalline and polycrystalline in terms of speed of sharpening and stone longevity.
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Lot of useful info, thanks :)
Yes I had read about poly and mono crystalline.
I think to have understood, that monocrystalline is slower but wears also slower. While Polycrystalline sharpen faster but needs a break in and wears faster.
Do you agree?

Lieblad said:
Unless you just dont have a powertool, I suggest grinding & quench every few seconds.
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Sorry, did you really mean "every few seconds"?
 
Depending on how much you want to spend you could get a stone from the hardware or a fast cutting Japanese waterstone. A file can work but it can also chew up the edge so it's not something I would suggest on any quality cutlery.

The coating on the File might be 72 HRc but I doubt the actual file is that hard. Marketing to make you think its better than it really is, same misleading info was releases when the DLC coating was first applied to knives.

Buy a stone and forget the file.
 
Yes, on power tools working towards the edge, every few seconds, the heat can't sink fast enough. You may even notice water boiling at the edge while grinding.
 
Jason B. said:
Buy a stone and forget the file.
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Any suggestion? I was suggested a Suehiro in 100. Waterstone, soft, it takes lot material away, just what I wanted, but apparently wears fast and during the job produces lot of "mud".

Skimo said:
Yes, on power tools working towards the edge, every few seconds, the heat can't sink fast enough. You may even notice water boiling at the edge while grinding.
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Ah, I had read something else, I thought he was saying "if you have no powertool, sharpen by hand every few seconds" :D
Yes, I have noticed the water boiling. I did not water constantly, because I did not think about it, but as soon as the metal suddenly changed colour I stopped and poured some water onto the mattock. Vapour in one sec. I had to submerge the mattock in water for some secs...
 
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yah ,that would be correct. the atoma stones may have a combination of mono and poly but i don't honestly recall. you can also pick up an 8" diamond wrapped grinder wheel in clearance at woodcraft on line commonly used for turning tools made of everything from low grade carbon through m4 and d2 to carbide. cbn stones are nifty as well but don't work with carbide
 
I picked up a Shapton Glass 120 recently and it seems to work very well and produce very little mud. That's a big plus because very muddy coarse stones can scuff the side of the blade. It's a very fast stone but also very hard so lapping can be tougher. The best way would the Shapton puck and lapping powder or another coarse stone.

On the cheaper side you have the Naniwa or Suehiro stone like you were recommended. These will be short lived stones that dish quickly so buy two of them, after use rub them together to fatten. Check out fine-tools dot com.

On the very cheap side you have the basic Aluminum oxide or silicon carbide oil stones, these can be very fast and would probably work very well for what you want.
 
I think it's important to remember that this gentleman is not talking about a knife, especially a nice knife. He's wanting to thin down a mattock. (digging tool)

There is just NO WAY that I would recommend a file for that job. I don't care how expensive or well marketed or how hard the file is.....there are much better alternatives for this job. I use files to cut my bevels on my knives exclusively. The Pferd Chipbreaker is probably the most aggressive file I know of.....they're about $35 plus shipping. I use them all the time and there is no way I am putting one to hardened steel. You mentioned you didn't want to use a machine because you might ruin the temper. Look, if this were a knife, especially a nice one, especially one that is very hard with thin geometry, then over heating the edge with a power tool would definitely be a concern. But you're talking about a mattock. Likely mild carbon steel that isn't very hard to begin with, that has lots of mass to it. I would have ZERO issues using powered equipment on such a tool! It's not like it's a $500 kitchen slicer.

If it were me, and for some reason I had to thin a mattock (without powered equipment of some kind), I'd take my previous advice and the advice just given by Jason.....go to the hardware store and fine a cheapo SiC sharpening stone. Above that, Smith makes some relatively cheap diamond stones. You said you had a 120 grit Lansky? Have you tried that yet? There is just no way I'm 1. not using powered equipment on such a job and 2. paying money for a top quality file only to have maybe half it's life (if not all of it) trashed because I wanted to thin a mattock. Especially when a cheap SiC stone will do the job probably much faster and much cheaper than a file.
 
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I guess I'll be one of the few advocating the use of files for this job, and for most jobs on low RC steel tools intended for hard use. I use files for setting bevels on my machetes, lawnmower blades, hatchets and axes, digging tools. I'd recommend cleaning any dirt off the tool first, and then firmly clamping the tool to a solid surface. Once the file begins to catch, it removes steel very quickly and cleanly and with a lot of control. Even with a coarse belt grinder, I'm not sure I'd want to put the wear and tear on it for a job like the one described when it can be easily done with a file.

The combination stones will be slow going by comparison. I wouldn't even use my 80 grit boat stone for a job like this, a 12" mill bastard will make short work of it.
 
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