use for old files

bob vaughan

Bob Vaughan
Senior User
Many years ago when I worked as an auto mechanic, I made a gasket scraper from an old file...I clamped it in a vise and broke it at about 6" long, ground the end straight then beveled it to 45 deg, then used the side of the grinder to grind the "teeth" about 2" back on the bottom side...it was/still is the best, easiest to use gasket scraper I've ever used.
I've got sort of that same thing but I ground the nose straight so I had two edges for scraping. Makes a fantastic glue scraper. I may have to try the 45º bevel on another file.
Grinding hardened steel isn't difficult but it is slow. An angle grinder and wet rag helps if one gets too aggressive. The angle grinder gets the rough shape but precise, it isn't.
 

Rob in NC

Rob
Senior User
Most knifemakers, myself included, will rough grind to 80% pre heat treat and the remaining after heat treating. So yes... you can get an edge. Keep water handy. One pass on the grinder, dip in water...over and over.
 

gator

George
Corporate Member
Many years ago, my uncle used to make hunting knives out of old files. I don't know his process but I have one of them and it is beautiful with a bone handle..
 

Rob in NC

Rob
Senior User
Typically will anneal the files to make them softer and then do your grinding, etc... then heat back to critical, quench and temper back so they arent brittle. But OP already stated that he doesnt have a forge. He's already stated that he tempered them back a bit so will still be hard, but not brittle, which is just fine. I've done the same before with files. Just have to be careful during the grinding process.
 

tvrgeek

Scott
Corporate Member
So, as a file, they are too brittle?
Would a propane torch heat the last inch or so to "critical" and then which quench method? Air, Oil, Water?
Of course knowing what "critical" is. I don't think my IR spot meter goes that high. I'll check.
 

Rob in NC

Rob
Senior User
If you've not tempered them back, they would be too brittle and the edge would chip.
Usually, heating to non magnetic and just a few seconds afterwards will suffice. As far as quenching, oil is safest. Water is a harsher quench. Make sure the oil (can use regular canola oil) is heated. With a file, though, if you are just going to make into a chisel or such, can just temper it back. Heat in an oven at 400 for an hour. May need two cycles at this. Look for a dark straw color. There are different precise temps, quenching media, etc for knifemaking... but I just stick to heat to non magnetic and do an oil quench. If it's a mystery steel that oil wont quench (such as a lawnmower blade) then I've done a water quench.
I'm not sure if I'm explaining all this well so if not and if you'd like, we can yak about it over the phone. I'm not an expert on it, but have been making knives for a few years anyway.
 

riggsp

Phil
Corporate Member
Grind a little and quench in water often to keep the heat down, and the edge will last.
 

tvrgeek

Scott
Corporate Member
I will test the 400 and non-magnetic. That's easy. I don't see where 400 would give a color change at all. But I can at least measure 400 degrees. My spot IR goes to about 1400.
 

Rob in NC

Rob
Senior User
The 400 is for tempering, not to quench. I'll give two scenarios here for makinga file to a knife
1. Anneal the file first to make it softer to work with. Heat to critical and allow to cool slowly either inside the forge or by putting it in sand or vermiculite.
2. Do your rough grinding, drilling any holes, etc.
3. Harden the blade by heating until critical and then quench
4. Temper back the blade by 2 cycles at 400 in an oven

Because you are already working with a hardened file, you can get by without the annealing and quenching.

1. Temper the file back by 2 cycles at 400 degrees. File should be at a straw color. Could even get a little purplish.
2. grind out to shape. It will be harder than if you would have annealed first so have to go slow and cool often. Be careful not to burn the edge or you will ruin your temper.

Here are a couple knives made from each of those methods.
First is a Scottish Dirk forged from a farriers rasp...
Next is a small dagger type knife made using the second method...
Both are functional as knives, though I had to be extremely careful with the tiny dagger to not ruin the temper.



Does that make better sense?
 

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Gotcha6

Dennis
Staff member
Corporate Member
When annealing and slow cooling has anyone ever had good results with other mediums such as wood ash or dry sand?
 

Rob in NC

Rob
Senior User
Dry sand, yes.... never heard of annealing in ash. Usually folks use vermiculite because it cools it very slowly.
 

tvrgeek

Scott
Corporate Member
I can do my grinding on my CBN wheel, nice and slow. My test is it never hotter than I can touch. I'll pick one and test today.
 

Rob in NC

Rob
Senior User
yep... never wear gloves grinding for that reason, if not for the safety aspects. Should be fine. Let us know how it turns out
 

Mike Davis

Mike
Corporate Member
I can do my grinding on my CBN wheel, nice and slow. My test is it never hotter than I can touch. I'll pick one and test today.
My CBN came with warning to use only on tool steel, regular carbon steel will clog a CBN wheel.
 

Gofor

Mark
Corporate Member
Wood ash works well, but first you need to screen it to get out any chunks and bits of charred wood. Becuae its so fine, you may need to bounce the container a couple times, or tamp it down to make sure you get even contact with the metal surface.
 

Mike Davis

Mike
Corporate Member

Re: Final report, CBN grinding wheels

« Reply #27 on: October 06, 2017, 02:20:36 am »

"I asked our Australian woodworkers what steels should be avoided on CBN wheels and they said unhardened only.
They gave me a long list of tool and knife steels they grind on CBN wheels, but in one word - any steel is OK except poorly hardened - the latter will gum up the grit. Tungsten carbide is another exception, but for a different reason - better done on diamonds.
Well, we have to conclude that the manufacturer's leaflet coming with the CBN wheels is incorrect in saying that high carbon steels should be avoided."



So, I found this and it looks like only the annealed carbon steel or other soft steels/metals are a problem.
Hardened high carbon steel should be OK to grind on CBN even though Woodworker's Wonders advises against it.
 

tvrgeek

Scott
Corporate Member
yep... never wear gloves grinding for that reason, if not for the safety aspects. Should be fine. Let us know how it turns out
I never wear gloves for the safety reason. Another common no-no is having a rag in your hand. My shop teacher had a story, do not know if true, of someone losing several fingers to a grinder. I actually hate gloves for anything for the loss of control. So, they do get beat up a little when working on my Triumph and the like.
 

tvrgeek

Scott
Corporate Member
Wood ash works well, but first you need to screen it to get out any chunks and bits of charred wood. Becuae its so fine, you may need to bounce the container a couple times, or tamp it down to make sure you get even contact with the metal surface.
Would not the carbon in the ash cause an issue?
 

tvrgeek

Scott
Corporate Member
Only blades and bits on my CBN. I have "white" wheels I can dress for everything else. Never ground any carbide. I guess diamonds is it. It used to be "green" wheels. It is said not to use diamond on edges due to carbon migration, but if kept "finger cool" that can't be a problem. After all, we use diamond honing plates. Never hotter than 212.
 

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