Thread: Metal files 101

Hi All,

The question that's NOT being asked, is what is the mechanism that make a file dull.

Looking at Pete's pictures, in particular this one

Attachment 191242

It looks to me like the teeth in the dull section have tips that are rounded over, hence reflect the light, rather than broken or worn down, and, the acid sharpened section has cleaner lines....

Maybe the acid etched away the rounded over "burr"..

Just a theory.

Regards
Ray

PS, if it was left over bits of material, it would tend to be in the gullets like the brass bit, not sitting on top of the teeth.. so I think cleaning is not a likely explanation.

My thought were always that the teeth were rounded over Ray, however there's not doubt there's a few breakages in the house too! Another thing that's interesting is the shadow line or at least darker area in the gullets of the acid treated area. That's especially noticeable in the second shot of the treated file.

Pete

That's probably the grey deposit that I was referring to. Magnetite?? Fe3O4??

Along with the arrival of the first batch of hand stitched rasps, there were some file samples as well. These will go out to a couple of members for assessment. If you wish to look at what these superb rasps can do, then see this thread, or check Claw Hama's review.

A Milled File, Medium + Chip Breaker


Same again, but lit from the other side to show the depth of gullet


A Milled File, Smooth (no chip breaker)


Same again, but lit from the other side to show the depth of gullet


An Engineer's File, Medium, Double Cut



An Engineer's File, Smooth, Double Cut


Saw Sharpening Files (there are numerous):


I haven't used them yet, but they certainly look the goods. IanW will be testing the Saw Files, DaveJ will test the Milled Files. Once Ian has worked out what sizes work best we are going to get some more samples, but these will have the Titan and Sapphire coatings applied to see what/if there is a cost benefit. I have a very strong suspicion that the coatings will be worthwhile, even though they are expensive - Vallorbe are already using the Titan coating on a range of their files called "ValTitan".

The point is this - if (say) a Sapphire coating makes the file last 2.5 times longer for 3 times the cost then it is worthwhile, once you factor in freight charges. The benefit is that you don't have to buy files as often, and that's very important for us Aussies getting stuff from Europe. If the coating has the same effect as it does on Rasps (yielding a 4x life) then it's obviously well worthwhile. The coatings also prevent rust, and I'm thinking that there may be a benefit in chip clearance (not sticking to the file as much).

Lastly - just revisiting my acid baths: I did purchase some new acid, but there was still no effect on that poor old Nicholson. It's just too far gone. What I did find out was if you have some aluminium chips stuck to the file you can just dip the file into a 30% strength HCL solution for 2-5 seconds and they disappear.

Lastly - just revisiting my acid baths: I did purchase some new acid, but there was still no effect on that poor old Nicholson. It's just too far gone. What I did find out was if you have some aluminium chips stuck to the file you can just dip the file into a 30% strength HCL solution for 2-5 seconds and they disappear.

As a matter of interest, how long did you leave the file in the acid?

Pete

2 hours I think - yes, it was two hours, as I made sure I followed your guidelines exactly.

Originally Posted by FenceFurniture

2 hours I think.

Interesting. I wonder if some steels are more prone to acid etching than others depending on their specific alloy content? Yes your file was a shocker, I can't see acid helping that number of dings and missing bits one iota, but I'm interested that after 2 hours you couldn't detect any etching at all. That was about the time mine was in and from the photos it's as plain as day. Did you leave just 1/2 in and 1/2 out like I did?

Pete

The higher the carbon content, the more inhibited the reaction is (Wikipedia - I think). Yep 1/2 and 1/2.

Ok, the one I used was a US made Nicholson. I have an almost identical file to the one I tried before, this time Australian made. I'll run the whole process again when I get a chance and see what happens this time.

Pete

Originally Posted by FenceFurniture

Today's tests:

File condition as at last night after tests:


After 15 minutes in straight HCL acid (more bubbles, but not a fizz):


After 90 minutes:



And then polished on the spinning wire wheel (Pic 1 repeated at the right for direct comparison). Note that the gullets have not been fully cleaned of the grey residue. This is because the wires are 0.28mm in diameter and the distance between the ridges is 0.59mm (17 ridges per cm). BTW, the file card wires are 0.45mm:



Using some geometric shapes in an Excel sheet I have determined that the spinning wires will go half way down the gullets (hence all the grey residue in the valleys), but the file card wires will only go less than a quarter of the way in. Hence the file card will only remove particles that almost fill the gullets, and it may not remove the whole particle.

RIGHT! Now I'm going to leave the bastard of a thing in overnight (will be about 15 hours).

Lemon Juice (Citric Acid):
I've just remembered something from many months ago. I was restoring some copper antiques with Lemon Juice that has common Salt dissolved in it (just wipe it over - it's brilliant). Anyway, I left the juice in one of those cheap & cheerful stainless steel food prep bowls, and after a few weeks it had eaten a couple of small holes right through. I'll try that next.

Got a pm from fencefurniture asking what the residue might be.

My guess is that it's pearlite, the iron/iron-carbide mixture that's present in all steels. The acid attacks the iron, and leaves the ceramic carbide behind.

Dunno how it passivates, however - maybe for a little while perhaps.

Just a Guess (TM)

eddie

Good man Eddie, thanks for that.

Originally Posted by FenceFurniture

Along with the arrival of the first batch of hand stitched rasps, there were some file samples as well. These will go out to a couple of members for assessment. If you wish to look at what these superb rasps can do, then see this thread, or check Claw Hama's review.

A Milled File, Medium + Chip Breaker


Same again, but lit from the other side to show the depth of gullet


A Milled File, Smooth (no chip breaker)


Same again, but lit from the other side to show the depth of gullet


An Engineer's File, Medium, Double Cut



An Engineer's File, Smooth, Double Cut


Saw Sharpening Files (there are numerous):


I haven't used them yet, but they certainly look the goods. IanW will be testing the Saw Files, DaveJ will test the Milled Files. Once Ian has worked out what sizes work best we are going to get some more samples, but these will have the Titan and Sapphire coatings applied to see what/if there is a cost benefit. I have a very strong suspicion that the coatings will be worthwhile, even though they are expensive - Vallorbe are already using the Titan coating on a range of their files called "ValTitan".

The point is this - if (say) a Sapphire coating makes the file last 2.5 times longer for 3 times the cost then it is worthwhile, once you factor in freight charges. The benefit is that you don't have to buy files as often, and that's very important for us Aussies getting stuff from Europe. If the coating has the same effect as it does on Rasps (yielding a 4x life) then it's obviously well worthwhile. The coatings also prevent rust, and I'm thinking that there may be a benefit in chip clearance (not sticking to the file as much).

Lastly - just revisiting my acid baths: I did purchase some new acid, but there was still no effect on that poor old Nicholson. It's just too far gone. What I did find out was if you have some aluminium chips stuck to the file you can just dip the file into a 30% strength HCL solution for 2-5 seconds and they disappear.

hi just looking at these files. is it to late to put my hand up to buy some?
thanks aaron

I've never heard of bathing files in acid before, but has anyone tried ferric chloride? Its a wonderfully "soft" acid and my go-to for etching damascus- just a thought. It can be bought from Dick smiths and maybe Jaycar for etching circuit boards.

Another thing to add to my list of things to do!

I don't have too many old files around as most of them get forged into something.

Ewan

Originally Posted by Ueee

I've never heard of bathing files in acid before, but has anyone tried ferric chloride? Its a wonderfully "soft" acid and my go-to for etching damascus- just a thought. It can be bought from Dick smiths and maybe Jaycar for etching circuit boards.

Another thing to add to my list of things to do!

I don't have too many old files around as most of them get forged into something.

Ewan

hi mate ive been meaning to use some blunt files for some thing. what do you forge your old files into. are you making knifes with the Damascus? sounds like they might be worth putting some photos up.
aaron