Disston Backsaw Rehab-2-Sharpening
I’ll be honest. The thought of sharpening all those little teeth, with their attendant geometries has always intimidated me. But so did tuning my first Stanley Bailey Type 11 smoother. And what I’ve learned from tuning my planes is that I understand my tools and the way they shape the wood on a much more intimate level. And that’s made me a better woodworker.
I wanted to have that same understanding for my handsaws. And I wanted to have the confidence and skill to sharpen my own saws any time they required it. To be and do less, I felt, would be to surrender craftsmanship to my fear of damaging the saw.
In any event, here’s a shot of the teeth before I cleaned up the plate.
If your experience is anything like mine, you’ll spend more time reading up on handsaw sharpening than you’ll spend actually sharpening your first saw. And that’s a good thing. You want to give yourself the best odds of being successful the first time.
These were the sources that I found most useful:
|Article-“Saw Filing–A Beginner’s Primer,” Pete Taran||http://www.vintagesaws.com/cgi-bin/frameset.cgi?left=main&right=/library/library.html|
|Article-“”Sharpening saws,” Bob Smalser||http://www.cianperez.com/Wood/WoodDocs/Wood_How_To/INDEX_How_To_pages/Smalser_on_SharpeningHandsaws.htm|
|Article-“”Saw Sharpening,” Ken Greenberg||www.calast.com/personal/ken/Saw%20Sharpening.pdf|
|Video-“Episode #7: Sharpening Part 3,” Bob Rozaieski||http://www.logancabinetshoppe.com/1/post/2009/09/episode.html|
|Video-“Saws Part 1: Techniques and Sharpening a Rip Saw,” Thomas Lie- Nielsen||http://www.youtube.com/watch?v=orPgaoF31ZQ|
|Video-“Saws Part 2: Sharpening a Cross Cut Saw & Setting Saw Teeth,” Thomas Lie- Nielsen||http://www.youtube.com/watch?v=flJMdpkcn5s&feature=related|
You’ll want to collect all the gear necessary to complete your sharpening to avoid the frustration of setting aside the job before it’s finished.
You’ll need the following:
- Files in sizes appropriate to the points per inch (ppi) of your saw (as detailed in the articles above and the diagram below). You can get them at Ace Hardware and http://www.toolsforwoodworking.com. Budget about $6.00/file.
- A saw vice to hold your saw steady (I built the shop-made vice detailed in the June 2010 issue of Popular Woodworking Magazine). Built from shop scraps, the cost is “free”.
- Some sort of magnification so that you can see what you’re doing. I bought some reading glasses at the grocery store for $20.00, but there are less costly ones out there.
- A saw set (ordered mine from lee valley tools), budget $32.00 which included shipping to the wiles of Colorado.
- Appropriate jigs (A. rake, B. fleam, C. file handle, D. file jointer fence—all “free” using shop scraps.)
If this is your first time sharpening, there are five steps to follow.
Step 1: Let’s get Jiggy
You’ll want to go to the 5-minute trouble of creating jigs and aids. I found them invaluable to keep track of which direction I applied the file. I can tell you after the fact, that filing my rip saws was a breeze. But for the crosscut saw I was rehabbing, I needed help to keep a proper orientation in x, y and z axes.
Jigs A and B will help you track the rake and slope of your sharpening. The diagram to the right will help you understand the direction of movement these terms refer to. (You can download this chart at toolsforworkingwood.com.)
A. Rake jig.
This is placed on the end of your file and will help you apply the proper rake angle to the teeth. For my crosscut saw, I used a standard 15 degree rake angle. (To create the jig, I followed the directions in Taran’s article.)
B. Fleam guide.
The first time I sharpened my rehabbed Disston 12″ backsaw, I placed a ruler on the bench at a 25 degree angle. The second go-around, I cut a kerf into a 3″ x 1″ block at a 20 degree angle (wanted less fleam) and placed it on the saw blade as a guide. This worked MUCH better.
C. File handle.
To avoid blisters and the pain of a file digging into your hand, you’ll want to fashion a handle for your file. I cut a 5″ length of oak dowel I had lying around and drilled a hole to fit the shank into. I compared my drill bit to the shank diameter and test drilled in scrap to find the best fit.
D. File jointer fence.
You can use a file bare handed to joint your saw, but I wanted the guidance that a fence provides. So I measured the thickness of my file and routed a channel. It was a bit big so I layered on masking tape onto the file until I got a snug fit.
Step 2: Joint the saw.
The red arrows below show that some teeth are shorter than others. You want all the teeth working for you in the same plane as you push it through the wood. To achieve this, I would joint my Disston backsaw. This is done by placing the file jointer fence flush against the saw blade and applying some pressure as you steadily run it across the full length of the blade. You don’t need a lot of passes. In this case 3 passes were plenty to joint almost every tooth top.
Notice the flats on top of most of the teeth in the picture below. Not to worry, shaping/sharpening would transform these into points.
Step 3: Shape the teeth
Full disclosure: I didn’t really understand this step, so I skipped it in favor of sharpening. As it turns out this worked fine for me.
Step 4: Sharpen the teeth.
I’ll be honest. The first sharpening was a bear. In retrospect, I wonder if this saw had been filed rip originally. When I filed it crosscut the fleam did not go on easily. I had to work at it. Maybe I used too high an angle (25 degrees initially) but that first sharpening took a while.
Your first tentative strokes will indeed take time. But you’ll be repeating the same motions, using the same orientations of the rake and fleam on every tooth. My Disston has 11 points per inch, which equates to 10 teeth per inch. So doing the math gives us: 10 teeth per inch x 12 inches = 120 teeth. After the first 40 teeth, I got into a rhythm, and the technique got much easier.
Step 5 (or 3.5 depending upon whether you want to set the teeth before filing or after): Set the teeth
I chose not to set the Disston’s teeth. While I had sharpened the teeth a few times, the set looked good and I felt it didn’t need it.
However, for illustrative purposes, I will use my Ebay Spear & Jackson 14″ tenon saw, which did need some serious setting. After sharpening the S&J, the tool left me speechless because the cuts were literally as smooth as a hand-planed surface. I was breathless too, because the tool would bind in the cut and require a lot of effort to push. Both symptoms screamed “SET ME!” according to my research.
I keep a log of my saws which notes their ppi, fleam and rake angles. The log guides my choices of files and adjustments to my saw set. My tenon saw’s 12 ppi called for the 12 setting on the saw set. Setting took 5 minutes following the instructions in the sources listed above.
Step Moment of Truth
Then it was time to test whether the time and energy I spent learning to sharpen paid off on my first attempt. In a word–Yes. The Disston cut finely, meaning that it cut slowly but left a very smooth finish.
However, I wanted a bit more aggressive cutting action to work through my sawing faster.
So I decided to sharpen it again.
I pulled out a 10 x loop to inspect the teeth before I started, and discovered that they had not been fully shaped on the first sharpening. The sharpened edges did not fully extend to the bottom of the gullet. So the second time, I applied firmer pressure to the file to more starkly define the gullets. I decreased the fleam angle to 20 degrees and used (jig picture in B above) an on-the-saw guide this time versus a ruler laid on the bench below the vice. This worked much better.
After the second sharpening, there were still some flats where I had jointed the saw. So I sharpened it again, and this time, it took. My error was that instead of the three strokes I gave each tooth, I should have done five to begin with to eliminate the flats.
When I tested the saw, I found that it was a bit harder to start the cut. But once started, it cuts as quickly as I wanted it to. Here’s a shot of the test cut.
It’s not as fine as the first sharpening but I like the results.
And here she is, ready for service in my tool kit.
–> 70–year old Disston saw—$22.43
–> Saw sharpening kit (4-files, reading glasses & saw set)—$75.00
–> The confidence and basic skills to sharpen my entire nest of saws—Priceless 🙂
Sharpening my crosscut saws was challenging but very doable. Filing my rip saws was as easy as it could be. And as I add more experience, I can try different rake and fleam angles to evaluate their performance on the woods I work with.
If I can do it You Can Do It
Believe me when I tell you that learning to sharpen my saws was much easier to do—with the aids of the resources I mentioned before—than I expected.
Now, I’m no master at it, but I do have enough of the basics down to keep my saws in working order. Better still, I have a fuller understanding of how my saws interact with the wood, and what adjustments to make to achieve different effects (rougher/faster cut versus smoother/slower cut, for example).
And when you think about it, isn’t that how the artisans of days past would have demanded that it be? They were paid for their output, so they needed to work quickly. They needed sharp saws to do that and they didn’t have time to piddle away on complex sharpening methods.
So if you’ve ever thought about trying it, add it to your list of projects. You’ll add a layer of skills to take your craftsmanship to the next level.
Wishing you sawing success!