Thread: Sharpening Rasps & Files

That's pretty much what we were told when I did metalwork in highschool ~mumblemubmvle~ years ago. It does weaken the teeth and they will tend to go blunt quicker, but it does put an edge back on.

And it only works a few times before the teeth are completely stuffed, so you can grind them off completely and make a cheap lathe tool or a chipping hammer, or laminate it with wrought iron & make a knife blade

Hi Robert, thanks for that link.

I've never tried vinegar, or that Muriatic acid....I should give it a go...

What I have tried is car battery acid. Works well. I'd buy, say, 2 dozern old files from the market,,,,, chuck them in a acid proof container of sorts, with the acid, bubbles come up, ,,don't breath in fumes,,, and check every so often,,,,the acid seems to etch into the sides of the files serations, which tends to sharpen them up....if you leave them in too long, the acid will totally destroy the file making it completely useless.

Out of say 2 dozern blunt files, maybe 15 of them are good for use again. Some better than others. I don't know why that is. Something to do with the kind of files I guess. But I'm yet to work that out.

In anycase, its definetly a cheaper way of buying them. Can get them for 50cents at markets....new, a file costs at least $10, yes ?

So yes, its a good method I think. The only thing I don't like about it is the fumes. Gave me a headache one day. Probably should try something milder like vinegar or pee.... ...'darling ! ..why are you peeing in that bucket ? ' could be a laugh in that.

I've yet to try it on rasps though.

(Just remembered !...I got to try out mallasis too. Thanks Robert)

I do not have a bucket of urine (SWMBO objected), but I tried vinegar. It takes some time - about two days, but the rasps are much better now.

Originally Posted by apricotripper

Hi Robert, thanks for that link.

I've never tried vinegar, or that Muriatic acid....I should give it a go...

What I have tried is car battery acid. Works well. I'd buy, say, 2 dozern old files from the market,,,,, chuck them in a acid proof container of sorts, with the acid, bubbles come up, ,,don't breath in fumes,,, and check every so often,,,,the acid seems to etch into the sides of the files serations, which tends to sharpen them up....if you leave them in too long, the acid will totally destroy the file making it completely useless.

Out of say 2 dozern blunt files, maybe 15 of them are good for use again. Some better than others. I don't know why that is. Something to do with the kind of files I guess. But I'm yet to work that out.

In anycase, its definetly a cheaper way of buying them. Can get them for 50cents at markets....new, a file costs at least $10, yes ?

So yes, its a good method I think. The only thing I don't like about it is the fumes. Gave me a headache one day. Probably should try something milder like vinegar or pee.... ...'darling ! ..why are you peeing in that bucket ? ' could be a laugh in that.

I've yet to try it on rasps though.

(Just remembered !...I got to try out mallasis too. Thanks Robert)

How long do you leave the files in the acid. Then how long before you neutralise the acid and clean off the rust. It is these itty bitty details which have stopped me from trying so far. That and waiting for a mate to make a stainless steel trough, which I now have.

That article was sadly missing on timing details. Although he does say that you may have to repeat the treatment a couple of times to get the file/rasp sharp. So redo those files that did not come up to expectations.
My guess would be that they were very, very blunt.

Regarding the fumes; work in the open with the wind at your back. No wind no work .

Rob.

Robert34, I've done this at work once before and we just kept checking the rasps till we were happy with the progress. We just rinsed the files in a mild caustic soda solution to nuetralise the acid then a thorough rinse in water and dry.
A stainless steel tank will be useless for this too. It is still made of steel which will react with the acid, especially if the acid is in the trough for any long period of time. What we used is one of the $2 cat litter trays (brand new of course). Works great and doesn't matter if anything bad happens to it.

Originally Posted by Wood Butcher

What we used is one of the $2 cat litter trays (brand new of course). Works great and doesn't matter if anything bad happens to it.

Hi WoodB!

Of course the tray is new - just use it for the cat afterwards

Originally Posted by Auld Bassoon

Of course the tray is new - just use it for the cat afterwards

Or you could let the cat use it first, and you do not need to buy vinegar.

Originally Posted by Robert34

How long do you leave the files in the acid. Then how long before you neutralise the acid and clean off the rust. It is these itty bitty details which have stopped me from trying so far. That and waiting for a mate to make a stainless steel trough, which I now have.

That article was sadly missing on timing details. Although he does say that you may have to repeat the treatment a couple of times to get the file/rasp sharp. So redo those files that did not come up to expectations.
My guess would be that they were very, very blunt.

Regarding the fumes; work in the open with the wind at your back. No wind no work .

Rob.

mustn't have been very windy. The fumes are particulary bad from battery acid. Seemed to be quite nasty, even during those few seconds you need to take to fish the files out.

Regarding time. I couldn't give you an exact time. It seemed to vary with the strength of the battery acid. And different files etched at different rates, if you know what I mean. In general, I just left them over night, and had a look at each in the morning.... and kept checking, every couple hours when I got a chance and fishing out the ones that felt ok when I rubbed my finger on them, leaving the others in.

The last batch I did was a couple of years ago, and I don't remember exactly how long it took.

My approach to it was pretty relaxed. I wasn't too worried about overdoing them cause their just so cheap, and conceeded to the fact I didn't have the time to wait around watching it happen, so it was ok if I wasted a couple. In which case I'd just use them for blade blanks.

Probably a good idea, if worried, to just do one at a time at first. Check every couple of ours, to get an idea of how long it takes. And maybe when confident with the time period, do a whole batch all at once. Thats what I've done, and that last batch has lasted me a couple of years.

Goodluck with it. I'd like to hear how you go.

Jake

Thank's Jake.

I was not sure if I could leave them in overnight or not. As I did not want to stuff up my first effort.

Timing does not seem to critical, just a matter of best guess. And you can always put them back in if a bit under done, and if overdone; make something out of the remaining steel.

Rob

Couple of other file sharpening threads here & here.


Cheers...................Sean