Files for saw sharpening

[Matt Radtke]

I've recently gotten my great-grandfather's Disston back saw and it needs to be sharpened. Looks to 13 or 14 PPI. My question is two parts, that kind of goes into one.

First, LN, toolsforworkingwood, and vintagesaws.com all seem to have different opinions for what size taper should be used, with TFWW being the biggest dissenter. Are any of these more wrong or right?

Second, the smallest I can get locally (aside from needle files) seems to be a 6" XX-slim from Nicholson, which everyone (including the chart on the back of the file package) says I should use something smaller. How bad of an idea would it be to use it? Or are there tricks to make it less bad?

Guess I just need a fair amount of advice on the topic. . .

[lowell holmes]

http://www.highlandwoodworking.com/search.aspx?find=triangular+file&page=4

http://www.lie-nielsen.com/catalog.php?grp=1351

http://www.leevalley.com/wood/page.aspx?c=2&p=32952&cat=1,43072,43089&ap=1

You need a 4" extra slim. Any of the links above will have them. Lee Valley has free shipping at this time.

I recently read that the file should be twice the depth of the tooth in order to provide a fresh edge when you rotate the file to sharpen the next saw.

I have two old Disstons, one was made in 1878 and the new one was made in 1923.
They both are sharp and cut a straight line. If you've seen the Lie Nielsen utube video on sharpening their saws, you should be in good shape.

I had to buy a LN saw before I knew what a saw was supposed to do.

Have fun!:)

[Don C Peterson]

I'll qualify my statement by saying I don't consider myself an expert...

Using the smaller files helps mainly for visibility, you don't have a large file blocking your view. The smaller the file, the sharper the corner too, so if you use a large file to sharpen small teeth, the bottom of the gullet won't get sharpened. Too much of a discrepancy between tooth size and file size won't work at all because the corner of the file will be too large to fit between the teeth.

I recall Bob Smalser recommending that for maximum life and utility your file should be sized so that half the surface of the file should be making contact with the teeth so that when you turn the file the other half is used. If you use too small a file you will wear down the file too fast, if you use too large a file you aren't using the entire cutting surface. Makes sense to me.

[Matt Radtke]

You need a 4" extra slim. Any of the links above will have them. Lee Valley has free shipping at this time.


See, the Lee Valley site is just what I'm "complaining" about. LV says for that size, a 4" extra slim. LN says 5" double extra slim (which seems to match up with vintagesaws.com). But for more fun, vintagesaws doesn't sell a 5" anymore and says their 6" is fine. GAH!!!!

[Ron Hock]

While researching and vetting my saw sharpening chapter (The Perfect Edge (http://www.theperfectedgebook.com)) I asked Mike Wenzloff (http://wenzloffandsons.com/) to read what I had and comment. He was meticulous and generous and I can't thank him enough. Here's what he said about files:

"In general, I disregard the notion of the flat face of a taper file being twice the height of the tooth. I think that the smallest file that will fully file the back of the next tooth is better. The back of the next tooth is actually longer than the face unless one is filing a 45 deg. rake. The point being, the larger the file, the larger the gullet. The larger the gullet, the smaller the tooth in both width and depth.
Most my files last for 20 or more saws. And I suspect that short of someone abusing a saw file (hard pressure on the return stroke) I am harder on a file than most people reading your book would be."

[lowell holmes]

I just ordered (4) 4" extra slims and one 4" double extra slim. I guess I should have ordered all double extra slims.
Ron, thanks for chiming in.
I've used files of various sizes on the same saw with no deleterious affects.

[Josh Bowman]

Don't get a file so small that it will wear more than 1/2 of its face. In other words if the file is the right size, when the file will no longer cut (makes that horrid banshee scream sound), you should be able to rotate the file to 2 new edges. And be able to do that once more or 3 times total. If the file face is to small then you will only be able to use 2 side and the other sides will have part of the file face worn out. I hope that makes since.
I have now sharpened lots of saws in the past few months. Get a good vise that will keep the saw from vibrating and hold it tight. I actually think you can make a wooden one with leather faced jaws that will work as well at any bought one. I kind of went nuts here and now have 4 vises plus a homemade one! Make sure you have very good light......and a light with a magnifier won't hurt, for beginning. I found myself getting lost on 12 ppi and above, but when I got the magnifier it helped a lot.
Oh, I agree with Hock….don’t drag the file back, you’ll flatten the files teeth and ruin it. Also don’t press down real hard, you’ll also ruin the teeth…….I went through a lot of files at first. You’ll know your doing right…..it feels right when you push the file forward, not to much noise and a good amount of metal removed. Having said that, watch the gullets and teeth height as you file, you can make an uneven mess. Just remember, you can always file the tips of the teeth even again (joint) and start all over. My first saw, I thought I would have to have the teeth recut. But I just kept improving my filing and touch and rejointed the saw, refiled until the teeth became very even. Now it’s my best saw.
Josh

[James Taglienti]

I use a 5 dollar needle file on my 12" backsaws and it gets them very sharp. In 3/4 stock it will cut about 1/2" per stroke.

[Josh Bowman]

There is nothing wrong with using smaller files. And everyone is right that it helps visibility. As I said before if it's too small, it's a matter of economy. When the 2 faces you’re using become worn-out, so is the whole file. This is a skill and you'll find that as you watch the teeth being shaped and can see the front cutting edge, that you can achieve very sharp results quickly. An old method of determining saws sharpness seems to work well. Hold the saws teeth on your palm, as if to cut and very carefully pull your palm back.....just enough to see if the teeth catch on the skin. If it's sharp the skin will have little pin pricks. I can't over emphasize having a tight vise and good light. The old timers would sharpen in front of a window and control the light with shades so as to high light the teeth. At first I found saw sharpening to be slow and tedious. It's now much faster but kind of therapeutic.

[Bob Smalser]

See the 4X and 4XX Slims in my file block below? Those are used for back and dovetail saws. Needle files also work, but are less efficient and may not provide enopugh gullet for blade durability.

http://www.sawmillcreek.org/showthread.php?t=66090

http://pic20.picturetrail.com/VOL12/1104763/17912799/280319351.jpg


I secure the saw in the vise and lightly joint it to see what I have. While the joint and teeth look well-maintained to the naked eye, this saw has faults typical of both commercial filing, and filing for sharp points at the expense of the joint. One row of teeth is shorter than the other in several places where one side was filed past the flats on the teeth made by the joint, and the saw was filed straight across by machine using a file larger than optimum for these 11 tpi crosscut teeth. The gullets are perfectly uniform, but are too large, making the teeth too short.

http://pic20.picturetrail.com/VOL12/1104763/17912799/280287215.jpg


Before we look at filing, let’s look at files. Saw files are tapered triangular files with 60-degree corners, come in several confusing sizes, and always have “1st-cut, single cut” teeth as these cut slowly but produce a finer finish than coarser “2nd-cut” and multi-tooth files. Vintage Saws and file manufacturer websites like Simonds International have helpful guides for what size file is best for each pitch of saw, usually expressed in tpi or teeth per inch. But what if you don’t have the recommended file? Can you substitute?


http://pic20.picturetrail.com/VOL12/1104763/17912799/280287213.jpg


Sure you can substitute. There are two factors guiding recommended file size. The first is you want the narrowest file possible so you can see the saw teeth better, yet you don’t want the file to use more than half its width when filing a tooth. That way you have three completely-sharp cutting surfaces on each file to use as each wears out.

http://pic20.picturetrail.com/VOL12/1104763/17912799/280287211.jpg


The second factor is gullet width. The wider the file, the wider the flat at each corner, the wider the gullet it will produce, and the wider the gullet, the shorter the tooth. Of course there are limits. A knife edge file would minimize the gullet, producing a taller tooth, but the blade would also be prone to cracking at the gullet, and there are a couple hundred years of trial and error behind those file size recommendations that shouldn’t be ignored.

But you can certainly substitute files. New files of acceptable quality are expensive, and excellent values can often be had buying boxes of NOS taper files in off sizes and 2nd-cut files. You can use the coarser 2nd-cuts to shape the teeth and finish with your 1st-cut files. 3-inch Regular Taper, 1st-cut files can be currently had for pennies each, and substitute nicely for 3 and 4-dollar 5-inch Slim Tapers and 6-inch Double Slim Taper files. Just be aware that switching file sizes on the same saw can change the shape of the teeth due to even minor differences in gullet width, and the same can be true when switching manufacturers of the same size file.