Thread: Saw sharpening files 101

Originally Posted by Brit*al

So we now know that there is no benefit in acid treating the files, but what about sand blasting? Check this out.

Sharpening Files published in Engineering, an Illustrated Weekly Journal,# June 28, 1878

It looks like that is essentially the process that Boggs (an American company) uses to sharpen files.

My take on it is that the biggest problem with bad files is that the teeth just crumble, which no amount of sharpening will overcome. Coarse grinding or sanding of the blank could possibly be remedied by such a process, but it would be far better (and likely cheaper) to prepare the blank properly in the first place.

From what I have heard (and this is second hand information, but it does sound likely), the main problem with sharpening used saw files is that they can do nothing to repair the broken teeth on the edges of the file.

The finer the teeth of the file, the less effective this method is. I don't know where that line is, though.

Originally Posted by Brit*al

So we now know that there is no benefit in acid treating the files, but what about sand blasting? Check this out.

Sharpening Files published in Engineering, an Illustrated Weekly Journal,# June 28, 1878

From the end of that article:

"About 4 horse power of 60 lb. steam used during four minutes, and one pint per minute of sand (passed through a No. 120 sieve), and the time of a boy are the elements of cost of the operation."

Ah, those were the days when children pulled their own weight...

Originally Posted by FenceFurniture

In short, the Citric Acid treatment contributed nothing positive whatsoever, and seems to have a very bad effect on lesser quality steel. After I had treated the files I noticed that they felt much “grabbier” (sharper) to the skin, and under a loupe of 8x magnification the treated files looked MUCH sharper and cleaner. Encouraged as I was by this I kept the caveat that this must translate to improved performance, and it did not – quite the opposite.
.

I have long questioned the use of citric acid on hard steels and on low alloy steels. I believe that citric acid, as well as electrolysis and "pickling" can cause hydrogen embrittlement in these types of steels, causing them become weaker and fracture easier. File edges that look and feel sharper may in fact also be weaker. I'm no expert on this, but became aware of this potential problem years ago and now avoid using citric acid on any steel that has an edge for planing, scaping, sawing, drilling etc.

Regular Taper - Heavy Taper, Extra Slim Taper, Double Extra Slim and Slim Taper

Maybe you can educate them on how to make a good file and solve the issue at the root???

Originally Posted by Glen C

I have long questioned the use of citric acid on hard steels and on low alloy steels. I believe that citric acid, as well as electrolysis and "pickling" can cause hydrogen embrittlement in these types of steels, causing them become weaker and fracture easier. File edges that look and feel sharper may in fact also be weaker. I'm no expert on this, but became aware of this potential problem years ago and now avoid using citric acid on any steel that has an edge for planing, scaping, sawing, drilling etc.

The problem is with spring steel, eg saws, dividers, springs ie anything under tension. Acid is primarily for de-rusting, and has limited sharpening scope other than files/rasps. Have not tried with auger bits - doubt will work.

Acid sharpening of files/rasps depends on the state of the item before dipping. Well used saw files are therefore likely to be a problem, cannot restore worn down corner teeth. Most other files/rasps - if not abused - work well after appropriate dipping.

Cheers
Peter

Remember this one where I broke one of the saw bolts? Well I managed to find a replacement. It took a bit of finessing to make it fit, but it worked out OK in the end.

I sharpened it at 19ppi (the smallest teeth I've tackled yet). I shaped the teeth with a Vallorbe needle file cut 4 and sharpened the teeth with a Vallorbe needle file cut 6 after setting the teeth. I used the cork from a bottle of Cava for a file handle. The needle files were so much smoother than a cut 2 needle file or a 4" double extra slim file.



I tried to get a close-up of the teeth, but my little point and shoot distorts the image a bit in macro mode.



IT LIVES!!! Thanks for the advice guys.

Jolly good, Andy!

QUEEN_138296801.jpg

Thank you ma'am.

Nice job! Looks like that old girl has shed many years (I'm talking about the saw ), and has a whole new life ahead of her....

Must try a cut 6 for the final sharpening bit, sometime. I've been using the 4s because that's the finest available locally. They do the job if you go over each tooth with a very light stroke to finish, but the surface isn't quite as smooth as I'd like to see.

Cheers,

Thanks Ian. I didn't find it as hard as I thought I was going to. It was a struggle to focus on the teeth, but now that I've sharpened a few saws, I found I was able to rely more on feel and the sound of the file than my eyesight. I sharpened it with 3 degrees of rake, but it is a bit grabby so I think I'll add a bit more when I've got time.

Nice saw!

Thanks Sawdust Maker.

Originally Posted by Glen C

I have long questioned the use of citric acid on hard steels and on low alloy steels. I believe that citric acid, as well as electrolysis and "pickling" can cause hydrogen embrittlement in these types of steels, causing them become weaker and fracture easier. File edges that look and feel sharper may in fact also be weaker. I'm no expert on this, but became aware of this potential problem years ago and now avoid using citric acid on any steel that has an edge for planing, scaping, sawing, drilling etc.

Hydrogen embrittlement is very unlikely to be a problem. Citric acid is a weak acid so it has a relatively low hydrogen ion concentration and as it is a low pressure/temp environment and there there is no subsequent overplating to trap the H₂ it will easily diffuse out of the metal once it is removed from an acid bath. If stronger acid was used and you wanted to be sure the acid and hydrogen are removed then 10 minutes in boiling water will get them all out.

A good reason not to repeatedly use acid is it will eventually make the teeth much thinner and thus weaker and more liable to break off.

What are peoples opinions of Vallorbe Grobet files? I am bringing in a hundred odd for the Aussie knifemakers, just the three sizes we use (checkering) I could set up as a dealer on here too and make them available if the interest is there.