Thread: Old farriers rasp: any annealing tips most welcome :)

'Evening everyone,

Having escaped last month from my little apartment into a house with a nice big garage/shop, I have finally begun building my forge and collecting the bits and pieces to do some blacksmithing at home. One project that will be coming down the pipe at some point will be turning an old farrier's rasp into a knife and (eventually, once my skills have developed a bit) a razor.

Obviously I won't want to be working on the rasp as-is as it's bloody hard. Any suggestions regarding annealing it to make it workable? Anything to make sure I avoid? I am familiar with the more traditional blacksmith's approach of eyeballing temps by colour and I lack accurate high-temp thermometers, so unfortunately #s won't be of much use to me. But if you have any advice that can be related to colour or magnetic properties I would really appreciate it.

No rush at all BTW. I need to finish building the forge then get used to using propane rather than coal, which all my other blacksmithing has used, so it will likely be quite some time before I tackle this project.

Thanks

No real life experience, but from what I have read heat to non magnetic and allow to cool very slowly in something like vermiculite. Not sure if it would be different with a farriers rasp. I am curious as to what other says since always good to learn something from those more experienced.

I'm throwing this out there hoping those who can verify, or refute the info will do so. I knew an old ironworker/welder who had done a lot of time in prison. He told me, 40 years ago when I was an apprentice, that he would take files, heat them cherry red, and cover them with lime. He said, IIRC, that he'd leave them overnight and that when they were cooled off they were flexible enough to be like spring steel where if you stabbed someone in the ribs, the blade would snake around the bones rather than break.

I don't know if this method of annealing is doable, or if the results of doing it that way would be as he described. You hear so much "stuff" as you go through life.

Prison shanks are bound by a different set of rules...

As to simple annealing, yes, heat to non magnetic, at least a dull orange and allow to cool overnight slowly. Vermiculite, the micaceous stuff not the styrofoam stuff, or wood ashes will do the trick nicely. It should be soft enough to grind a lot more easily.

I would recommend removing the "teeth" of the rasp. It's too easy to leave a cold shut without realizing it and when heat treating the blades that result from the work, sometimes those shuts can lead to unwanted surprises.

"Jimmy's Floppy Shiv Co."

With prisons being such a growth industry, there's probably a buck or two to be made there.

Thanks guys - that was what I was thinking, so it's reassuring to have confirmation. And thanks for the teeth recommendation - I hadn't thought about the possibility of them presenting potential problems. Too bad as I think they would look great on the shank. Ah well...

I've quenched a knife made from a file that had cold shuts. After the quench, the blade had a couple of marble sized pustules

Originally Posted by Bruno

I've quenched a knife made from a file that had cold shuts. After the quench, the blade had a couple of marble sized pustules

Pustules?! Cripes... this is getting worse!

Been there, done that.

A farrier's rasp is not a good candidate for a knife or a razor. They're case hardened, which means that the hardness is only a few molecules deep into the rasp.

You can easily anneal one by heating it cherry red and letting it cool on its own, that is no quench nor blowing air. Just set it on something and let it cool. Then you'll have a dead soft rasp looking object you can abuse at your leisure without wearing your grinding belts and stones as quickly.

My recommendation is to get some good steel and start fresh. By doing that you can look up the process for working and heat treating. It's a crap shoot with a file. It may work, or you may gain a lot of experience and practice for the next one.

When I ran my smithy and made knives, I sought out old circle saw blades 24" and larger. 99% of those were made from L6 steel. L6 will anneal down to around 36 and you can make it go to 62-64 on the Rockwell scale. It'll cut glass at that hardness BUT it is brittle. So are most razor blades.

There are some knife makers out there that have made serviceable knives from files. They told me it required a fast quench, both at heat treating and tempering. I had no luck at when I tried and I burned up several old files trying.

I wish I could still swing a hammer and beat some hot steel. Those days are behind me and I can't afford a trip hammer. :/

I have used files and rasps, the nicholsons are the best of the lot they are 1095 carbon steel. as for annealing I used a blanket of kaowool avalible at most knife making suppliers and all forge makers have it. the above info is correct and the recommendation you get a good steel is also. 1095 isn't that expensive, starting out I would recommend you use 1084 or 1075, either can be quenched in water and yield a knife you will be proud of, heat to non magnetic and quench, then three 2 hr cycles at around 450 degrees to draw it down and you have made your blade. I used a disc harrow blade once heat to non mag and buried it in dirt to anneal it, the dirt was under a firepit that was very warm though to start off and the disc was heated in my old champion coal forge. I still have the forge but no coal, switched to the atlas mini forge and haven't looked back. I built three forges on my own and always ended up spending more on each of them than the atlas cost ready to go out of the box just add lp gas and a match to light, go to storm the castle and look at the atlas forge page, that is my forge, while there look under knives made by web visitors and see what I make.
i get my steel from the new jersey steel baron, aldo has fine steel.

I had a co-worker to give me 6 of them (he is a part time farrier) for a knife. I don't run a fireplace, so ash is out for me. My intent is to get a bag of vermiculite myself for stock removal...but if you are going to work the steel on the anvil just take it to non-magnetic and hammer away.

I haven't made it to the shop since I received the files unfortunately...