Advanced Saw Filing and Restoration

Filing and Restoration Part II

Bob Smalser

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This blade isn�t heavily rusted and isn�t pitted, so I forego phosphoric acid to seal the pits and merely clean the steel using 4 grades of Scotchbrite in sequence lubed with mineral spirits�

�followed by a green rouge buff against the direction of sanding to restore some shine.

Because I�ve shortened the saw the etch will be off center and unsightly to my eye, so I�ll blue the blade to hide it. But this is a good opportunity to demonstrate how to raise an etch like the faint one you see here.

To raise an etch, first avoid sanding it without using a sanding block when you clean the saw. Then degrease after buffing using mineral spirits followed by stronger trichloroethylene, and apply cold gun blue from a sporting goods store to the area of the etch. Follow the instructions on the bottle for curing and oiling.

After the blue cures, simple rubbing with a sanding block and 600-grit wet-or-dry paper lubed with WD-40 or honing oil will reveal any etch remaining. All these bluing solutions will rust if not oiled, some badly, so don�t omit it.

I then phosphate blue the entire blade, using the procedures I detail in a previous article on rust proofing tools. This type of blue applies a layer of rust-inhibiting phosphate to the steel, which also slightly fills the scratches and grinding marks present, making the blade a bit slipperier. You can read more about this at Brownells.com.

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.

Jointing insures all the teeth perform the same amount of work during cutting and involves more than just regulating tooth height. When the tooth line is wavy as shown above, the saw drags as teeth on the forward slope of a bump bite wood, and those teeth wear more quickly.

Continued�

Re: Filing and Restoration Part III

Bob Smalser

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This tooth line isn�t perfect either close to the tip, but it�s more than adequate for efficient sawing. Keep in mind as we go that my goal isn�t perfect saws, it�s perfect sawing, and there are differences between them.

Jointing is where you add or subtract �breast�, the amount of crown in the tooth line. Crown breasted saws are more difficult to joint, but rake sawdust more efficiently and crowns are always most pronounced on saws for green wood with gummy sawdust like the old one and two-man falling and bucking saws once used to harvest trees. Here I show a saw with a light breast on the left, a full breast in the center, and a straight or unbreasted saw on the right.

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?

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.

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.

Saws are filed in the stages detailed in several on-line articles on basic saw filing, like Pete Taran�s at the Vintage Saws website:

1) Jointing to even tooth height and straighten or fair the tooth line or breast.

2) Shaping the teeth to even the size of the flats made by the joint and set the rake angle.

3) Filing the �fleam� or cutting edge bevel angle until the flats disappear, creating sharp teeth of uniform height.

The major benefit of sharpening your own saws is you can tune them for how you use them. I usually work outdoors in damp, air dried wood and use hand saws where the mass of the work piece and the required angles and finish often preclude the use of power tools. Often 30 linear feet at a time too, driving study and experimentation in what makes the most efficient saw for my tasks. Accordingly, my saws are generally filed with the full crowned breasts and sloped gullets my boatbuilding family has used for generations.

Here are two identical 4 � tpi rip saws. Identical except the saw in the foreground clearly has taller teeth, and also a slight back bevel on the rear edge of each tooth. Seen at a different angle they look almost Japanese, and that�s probably not a coincidence. It was filed holding the file at a 45-degree angle to the blade, instead of straight across or 90 degrees to the blade like the saw in the background was filed. The geometry of a tri-cornered, 60-degree file is such that the greater the angle it is held at, the taller the tooth it produces. Brent Beach has a website that examines sloped gullets in more detail, including their history and accurate engineering drawings that better demonstrate their geometry.

I find the taller teeth work more efficiently in the wood I use. They bite a bit deeper and rake damp sawdust a bit better, and the back bevel that sloped gullets produce on rip teeth score the wood on the back stroke for easier removal on the front stroke. You�ll have to try them and see if there�s any benefit with the woods you use. Either way, how to file sloped gullets isn�t described anywhere else and they are another tool to place in your kit if you ever feel you need them.

When changing a saw to sloped gullets, I combine the steps of shaping the teeth and filing the fleam angle into one step, and concentrate on �filing to the joint� instead of equalizing the size of the flats made by the joint and counting strokes. Accordingly, I don�t use carbon black or other aids to insure I don�t skip a tooth, as skipping a tooth doesn�t matter when concentrating on the joint. I also tend to file one side less than I would when filing conventional teeth, switching sides more often, and sometimes even rejointing if I make a mistake and file a tooth past its jointing flat. Notice I have my usual fleam angle scribed into the jaws of my saw vise. I prefer a shop-made wooden vise with long jaws because I prefer to file while standing and I can file an entire side without having to move the saw in the vise.

Continued�

Re: Filing and Restoration Part IV

Bob Smalser

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On the first passes I�m hogging off a relatively large amount of steel, and am concentrating more on getting out my gullets, establishing a uniform rake angle and not filing past the jointing flats than I am about the fleam angle. I�ll emphasize the fleam later on my final passes when filing is easier, and I may even change the rake angle later after testing the saw on wood.

Keeping your angles constant when changing sides takes practice, and it�s also useful to move your work lights so you can clearly see the jointing flats.

Don�t continue filing if you can no longer clearly see those jointing flats. Take a break, move your lights or both. Also don�t hesitate to rejoint if you make a mistake and file past one. Moreover on saws like this one with short teeth and one entire row of even shorter teeth, you often have to compromise your initial jointing or not leave enough gullet on the short teeth to rest the file in, which is necessary for basic tooth spacing. You can see here that even after a full pass on each side, one row of teeth remains taller than the other, so rather than attempt too many tasks at once with the file, I rejoint and begin again.

I generally set the teeth before my final pass on each side of the saw so any damage caused to the cutting edges by the saw set is removed. Here you can see several small jointing flats remaining on the top of the teeth. When setting, I�m careful to place the plunger of the sawset at the same spot on each tooth, and when possible slightly back from the cutting edge bevel to minimize damage. And yes, although these Acme saws were designed to run without set, if a tad of set makes your saw more efficient on the wood you cut, then you can add a minimal amount without damage by using the lowest setting on your sawset.

On my final pass to eliminate the remaining vestiges of jointing flats, I do so by leaning the file into the backs of the teeth rather than continue to file rakes and fleams. Uniform rake and fleam angles and their cutting edges are important, the backs of the teeth aren�t when your only objective is sharp points on the teeth.

I make some test cuts in relatively hard, air dried Douglas Fir at 12% moisture content to insure the saw cuts smoothly and accurately to a line before stoning off any wire and flash caused by filing. When filing sloped gullets for the first time, you may tend to file in more rake than the blade will take, so be prepared to put the saw back in the vise and make another pass on each side to reduce it.

The finished hybrid panel saw. Cost? Six dollars, one file, and a couple of evening hours.

My short saws don�t get used much, but can be handy. They also can be practically free, especially when among the #120�s, #12, #16 and #88 shown it�s hard to tell which if any began life as a short panel saw. ;)

Thanks once again for your excellent work

Paul Kramer

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Excellent. Thank you.

Tony Augruso

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Recommend as a WC Article

Jim Shaver - Oakville, Ontario

>Thank You Bob,

I really appreciate the time and effort it took to put this together...I would love to see this in the Article section here....again thanks for sharing your knowledge and experience.

Take Care,

Jim

Re: Filing and Restoration Part V

Bob Smalser

>I always leave something out of these first drafts.

When filing sloped gullets on rip saws, you are putting a slight bevel on the back of each tooth, creating a slightly sharp point like on crosscut saw instead of the flat chisel point of a rip saw. To compensate, the set must be in the direction of the bevel so the point made by the bevel leans outward, creating the desired chisel point.

My example 4 1/2 tpi rip saw was filed with more rake than usual for a special purpose. Here you are looking at the teeth from the front.

Thank you Bob!

Scott Burr in Ben Lomond CA

>I realy enjoyed this post. Thanks for taking the time to pass your knowelege on us.

Re: Filing and Restoration Part V

Marv

>Hi Bob,

I'm used to seeing teeth that have evenly filed angles. The teeth in your picture appear to have an extra little angle up at the top of each tooth. Is that caused when filing a sloped gullet?

Also some of the teeth look kind of ragged. Are those ragged edges burrs or is it perhaps your camera playing tricks with such a closeup shot?

Did I understand you correctly when you said you use blueing to reduce the chance of rust but it needs to be kept oiled or it will have a greater chance of rusting? If that's the case, why not just keep it oiled without the blueing? Does the blueing wear off with use? Is it easily scratched? I like the idea of using it for enhancing the etch though.

Thanks,

Marv

Wire edges? Bluing? Where's the meat? *LINK*

Bob Smalser

>First, below is a link to the latest draft of this article, as this site doesn't have an edit feature.

And here are the main arguments against sloped gullets you either originated or agreed with earlier:

".... Over all capacity for moving waste is not improved over a "normally" filed saw. What tooth depth is gained on one-half the plate thickness is balanced by the loss of gullet depth on the other half of plate thickness."

"From my perspective, I will not file a saw using sloped gullets. Just another angle to be concerned about that serves little or no purpose. Handsaws are designed for only one thing and that is to produce sawdust.

While one side of the gullet is made deeper the other side is less deep.....The sloped gullet actually impairs the process of moving the sawdust downward. "

Now, does it really look like there is no overall tooth height improvement because the gullets alternate in height, offsetting it? Looks like almost a third to everybody else who looks at them....and from the higher of the two gullet lines, too.

And like you said, it all adds up to 60 degrees. Or does it really on a 45-degree slope? But yes, I agree all the file angles add up to 180 degrees, however they are affected by slope. So given the same slope, whatever degree of height improvement was gained by the 4-pt teeth is also gained by the 11-pt teeth, it's just more difficult to see in those itty-bitty teeth.

Like filing conventional gullets, stoning off the wire edges and curing blue finishes are in earlier articles on the basics. Sloped gullets is really a minor feature of this article, a more important point made several times is that filing for sharp points is often done at the expense of the joint, and a high percentage of both machine and hand filed saws have a significant number of short teeth doing little during the cut. That's the odd angle you see on the backs of some teeth...from tipping the file into the back to eliminate the last vestiges of the jointing flat without filing the fleam and shortening the opposite tooth that's already the correct height. Filing to the joint.




Advanced Filing

Anyway thanks, Marv *LINK*

Bob Smalser

>I incorporated your sawdust argument into the article. Thanks again.


Advanced Filing

Re: Anyway thanks, Marv

Marv

>Hi Bob,

Somewhat off topic.....Did you know you can saw a handsaw blade using a sharp hacksaw? I saw your picture of grinding off the end of a saw blade. Next time you need to do that, just clamp the blade flat on your workbench with a piece of wood on top with the end of the blade extending off the end of the bench and saw at about 25 degree angle to the blade.

I evened up a 10" backsaw blade, removed about 3/8" full length of the blade with a hacksaw. Sawed it to a scribed line. I finished the sawed edge on a belt sander then filed in new teeth. (no sloped gullets though)

Marv

Hey, thanks, Marv, for this tidbit

Bill Houghton, Sebastopol, CA

>I can now picture cutting up some of the old, non-valuable, worn-out saws in my collection for scrapers, and particularly for the 5/8" wide blades for the Stanley version of the scratch stock.

Re: Anyway thanks, Marv

Tony Zaffuto

>Bob and Marv,

To both of you guys: Thanks for respecting one another and not attacking each other's expertise. It is truly refreshing to see guys with different methods contributing to those of us without your knowledge and further acknowledge the other's capabilities.

If anyone is wondering what I'm talking about, just look at FWW "Knot's" forum (handtool section) and see how some posters vicously attack one another (and for that matter anyone who enters their domain). I'm surprised FWW lets this go on, but it is basically disgusting.

Grinding doesn't bend the saw.

Bob Smalser

>Thanks, I'll have to try the your hacksaw technique, but I find most shearing and cutting operations only add to the hammering and tensioning problems already there.

Re: Anyway thanks, Marv

Skip in Falls Church

>I needed to make a small scraper a few days ago and found that metal shears work really well for cutting smaller pieces. They seemed to work especially well for cutting the teeth off. I oriented the cut so the teeth went to the side the shears curl upward and it worked like a dream. The thin piece with the teeth curled up on their own and it was easy to cut to the line.

Skip

Re: Filing and Restoration Part IV

Brian Sullivan - Montreal

>Wow - Thanks for the article.

Restoration ?

Todd Hughes

>Looks like you made an interesting and useful saw out of some parts from other saws that you modified but restoration?.....

If I took an old wooden sail boat, cut the mast off it, shortened it in half and put an outbord on it after painting it blue because I wanted a blue motor boat would that be an advanced case of sail boat restoration , eh? .......Todd

Restore to "useful" or "collector" condition?

Bob Smalser

>Not my lane, Todd. I write these strictly for users based on what I do to my tools to make them useful in a boatbuilding operation.

Re: Grinding doesn't bend the saw.

Marv

>Hi Bob,

I have found that when grinding or sanding without using some kind of heatsink, the blade will sometimes warp. But using a hacksaw doesn't produce but very little heat and it is less nerve wracking than a huge amount of grinding. When I need to sand off only the teeth on a backsaw I clamp a bar of aluminum on each side of the blade with the bottom edges of the bars located where I want to sand to. I only use a hacksaw if I'm removing alot of metal.

I can saw off the end of a handsaw blade in about a tenth of the time it would take to grind it off. At my age I'm always trying to come up with faster and easier ways of doing almost everything.

Marv

Re: Anyway thanks, Marv

Marv

>Hi Skip,

With my luck, the blade would end up with a long bend from end to end. Also I don't have a shear. Once you put a bend in a backsaw blade, it's nearly impossible to straighten it.

Marv

Re: Restoration ?

Marv

>Hi Todd,

I prefer using the word "recondition" when discussing reworking a tool such as a handsaw in particular. If it is rusted and has other major damage it's pretty much impossible to "restore" it. Meaning, restoring it to it's original condition. Anyway, that's what "restore" means to me. Reconditioning, to me, means to make it useable again. With so many reduntant words in our language, I'm sure there are a dozen other words that could be used to describe the same thing.

Marv

I'll have to try your method, thanks. And... *LINK*

Bob Smalser

>Buffing also warps the sawblade badly, but if it's tensioned correctly it always comes back dead straight after it cools. If it's not tensioned correctly it's just like one bent over the auctioneer's knee so it will look good....flex it fully in both directions and the defect magically reappears.

Here's an article on phosphate treating steel for rust resistance. Phosphate blue gets more durable with age under oil. If I let those sawblades hang for several weeks before filing, the saw vise wouldn't rub it off at the jaws.

Ain't perfect, but nothing is perfect. 20 generations of gunsmiths treating bare steel with one manner of controlled rusting or another aren't wrong. If you use your tools in the rain like I do, it's the cat's meow. I durn near ruined a new L/N plane once by forgetting what house plants they are and treating it like my blued planes.

Last, I'm not trying to compete with saw makers of filers in anything but recording and passing on old skills. I rarely sell saws or tools, and don't sharpen for anybody else but me and my crew, all family. What we do is build boats, among other wooden things, and have since 1957 in one manner or another, beginning with the tree and continuing a family practice that goes back several generations. I learned how to file saws in the late 1950's from a boatbuilder uncle who learned from his carriagemaker father in the 1920's, when sloped gullets were more common that Foley machines. Those gents made their living using Disston 7's they bought by the dozen every day of an annual 200-day building season, and had a vague idea what they were about.

Sloped gullets are how those old pros filed their saws, and why commercial saw vises from that era articulate to 45 degrees away from the filer. If anyone today thinks those old guys were merely hidebound and weren't counting strokes and comparing saws during cuts of 50 linear feet or more, they are wrong.


Rustproofing Tools

Todd, ROFLMAO

Stephen Shepherd in the State of Deseret

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