I’ve been hesitating to post this entry on my Saw Talk blog series, basically because I don’t feel I’ve sharpened enough saws yet to make any recommendations to others. Instead, I thought I would take the opportunity to point you to some websites that I have found helpful. I have read most of the information available on the web on this subject and the links below are what I consider to be the best information for those new to sharpening. If you are serious about finding out about this subject, I highly recommend you read and inwardly digest this material.
From Matt Cianci on WKFinetools.com:
I thought it might be helpful if I pointed out some of the things I’ve realised are important when it comes to sharpening saws, so here goes:
You must use the right size saw file for the number of teeth per inch (tpi). The number of teeth is sometimes expressed as points per inch (ppi) and you should know that:
tpi + 1 = ppi (e.g. If it is written that a backsaw is 13ppi, then it is also 12tpi)
Online stores that sell saw files usually have a table that explains which file to buy for each tooth pitch.
It is also important to perform the steps involved in saw sharpening in the right order which is:
However, depending on the condition of the teeth before you start and whether or not you intend to change the tooth geometry, it might not be necessary to perform all of these steps. For example, if the teeth are in good shape and all you want to do is touch them up so they are sharp again, then you only need to perform steps 4 and 5 and 10 minutes should see you done. You can usually sharpen the teeth on a saw 3 or 4 times before it is necessary to re-set the teeth.
One thing I’ve realised as I’ve researched saw sharpening is that there are as many opinions as to the right tooth geometry for a given saw as there are people who file saws. You hear things like:
”I like to add a touch of fleam to rip teeth.”
“A little rake makes ripping easier.”
“Adding slope creates more space for the sawdust and helps move it up the side of the plate.”
Now I’m not saying that these people (who shall remain nameless) don’t know what they’re talking about, because they do. What I would like to point out though, is that the most important aspect of saw sharpening is that the teeth end up SHARP. Sharp teeth will cut wood regardless of whether they have 8 or 10 degrees of rake, 0 or 5 degrees of slope, or 6 or 8 degrees of fleam. After you have filed a few saws you will start to appreciate how rake, fleam and slope influence the cut of a particular saw, and you shouldn’t get too hung up on the optimum degree settings for each of these parameters when you first start out.
On the face of it, a backsaw is a pretty simple piece of kit isn’t it? It consists of a saw plate, a handle, a back or spine and two or three bolts. Whilst that’s true, there are many additional factors that influence how well a backsaw will perform in a given situation. Here are some of them:
- Sharpness of the teeth
- Degrees of fleam
- Degrees of rake
- Degrees of slope
- No. of teeth per inch
- The straightness of the toothline
- Saw plate thickness
- Amount of set per side
- Hang angle of the handle
- Spine weight
- The balance of the saw
- Handle comfort and fit
- The cant of the saw plate (if present)
- The angle you approach the cut
- Your ability to start a saw
- Your ability to cut to a line
- The type of wood you’re cutting
After reading the above list, you might be forgiven for thinking that there is more to this saw sharpening lark than you first thought, but let me say it again – SHARP TEETH WILL CUT WOOD. Even if all the teeth are not exactly the same height or if the tooth geometry is less than perfect, SHARP TEETH WILL CUT WOOD. After you have sharpened a few saws, you can start to experiment with some of the other factors that can influence the saw’s effectiveness. I bought the backsaws that I’ve restored in this blog series because I wanted to learn to sharpen and maintain my own saws and play with some of these factors to see firsthand how they affect a saw’s ability to cut. I’m sure you can appreciate now why I bought as many as I did.
So armed with all this information and a good helping of commonsense, I created a spreadsheet. The column headings were:
- Make and length of saw
- Filing (i.e. Rip, Crosscut or Combination)
- Teeth Per Inch
- Rake angle
- Fleam angle
- Slope angle
- Plate thickness
- Depth of cut at the toe
I carefully measured these details on each of my backsaws and recorded them on the spreadsheet. Then I inserted a new row for each saw and after much consideration, recorded the details of how I intend to file each saw (shown below in brown text) in order to end up with a versatile set of backsaws that will cater for all my needs.
As I’ve already mentioned, I’m new to sharpening saws. I hope I’ve got it right, but the nice thing about learning how to sharpen your own saws, is that you can always change them again.
Thanks for your support. As always, I welcome your comments, be they good or bad.
-- Andy -- Old Chinese proverb say: "If you think something can't be done, don't interrupt man who is doing it."