Step 3: Shape the Hand Saw Teeth (If needed)
The shape of the teeth determines the performance and use of the hand saw. No one tooth shape is the “best” shape, and different woods and different jobs require a different shape. For example, a rip tooth shape (as mentioned above) is better for cutting along the grain of the wood (like a chisel) and a cross cut tooth shape is better for cutting across the grain of the wood (like a knife). Several terms are imperative to understand if you want to shape your hand saw teeth correctly for your given job:
As the above graphic shows, rake is the angle that the file slopes back from 90 degrees. Both rip saws and cross cut saws can have rake. Rip saws generally have 0-8 degrees of rake and Crosscut saws generally have between 8-15 degrees of rake. A 90 degree, vertical tooth would have zero degrees of rake. The less rake a hand saw has, the more aggressive it cuts, but the harder it is to start and cut. Laying the tooth back a bit with a slight rake angle will make the cutting easier, but less aggressive. A high amount of rake will move really smoothly through a cut, but it won’t cut aggressively. Balance is key. Ideally you would have multiple rip-toothed hand saws and multiple crosscut-toothed saws (like some people do) and have different tooth geometry for different jobs. But most people will only be able to afford a few hand saws. So there are some good general purpose recommendations for the most common types of work. Here’s a chart to help you decide which rake angle to add to your hand saws when shaping the teeth:
|Crosscut Saws||Rip Saws||Back Saws|
|Softwoods||8-15 degrees|| 0-6 degrees||12-16 degrees|
|Hardwoods|| 8-15 degrees||6-10 degrees||12-20 degrees|
A 12 degree rake angle is a popular angle for crosscut saws.
Fleam is the angle at which you would file across the saw. A zero degree (or very minor) fleam is used on rip saws and the triangular file sits perpendicular to the saw. As soon as the file is turned left or right, fleam has been introduced. Fleam is typically only used for crosscut saws, as it is what creates the knife shape on the teeth. Here’s a chart to help you decide what fleam angle you may want to add to your hand saws when shaping the teeth:
|Crosscut Saws||Rip Saws||Back Saws|
|Softwoods||20-25 degrees||0-6 degrees||20-30 degrees|
|Hardwoods||15-20 degrees|| 0-6 degrees||15-30 degrees|
The fleam angle can be drawn right on the saw vise, on tape, or on a piece of paper that sits right below your saw vise. With the paper guide, you can move the paper along the workbench as you progress down the saw teeth.
A popular fleam angle for most woodworkers is between 15 and 20 degrees. You can download my free printable PDF sharpening guides here:
The Veritas saw filing guide that was shown in the tool section also helps with the fleam angle and rake angle. A “Sash”, or hybrid saw usually has a 10 degree fleam angle and 10 degree rake angle.
Slope is the angle at which the triangular file rests on the saw plate. See the above animation. For almost all hand saw sharpening, just keep the slope perfectly horizontal (perpendicular to the saw plate).
Shaping the teeth
If your hand saw teeth have been shaped already, then reshaping is unnecessary (assuming you want to keep the same shape), and you will only need to lightly joint (step 4 below) and then file for sharpness (step 5 below).
Once you have determined the rake angle and fleam angle, set those angles on your block guide or commercial file guide, and start shaping the teeth. I like to use my Veritas filing guide with the paper guide to give extra consistency. If your saw teeth are already shaped to the angle you prefer, then you can more-or-less just follow the existing shape, and skip this step. Sit or stand near a window, or next to a good lamp.
Make sure the saw teeth are just peeking up above the saw vise, to avoid vibration. Get them level to the vise, and as low as possible. Start filing at the heal of the saw, and work your way to the toe of the saw plate. This way your ugly shaped teeth will be on the least-used end of the hand saw! No matter how long you’ve been sharpening saws, your final strokes are always nicer than your first strokes. You eventually get in a consistent rhythm and muscle memory.
Some people like to run a black marker along the tops of the teeth to measure your progress. If you jointed your teeth before this step, the fresh shiny metal will help you measure your progress. It’s also a good idea to mark each of the three triangular file edges with black marker or white grease pencil. This will ensure that you fully wear out one edge of the file before using the next two edges.
For Rip saws, you can file all the teeth from one side. For cross cut saws, you will need to file every other tooth from different sides. So start from one side and file every other tooth, then file every other tooth from the other side. You will need to adjust your filing guide when you move to the other side of the saw file. File the face of the tooth that is pointing away from you. Use a push stroke, holding onto the file handle with one hand and the file guide with the other hand.
The number of strokes required for the initial shaping can vary, but for newly punched teeth, like in the above video, 2-3 strokes per tooth should shape the tooth most of the way.
After you finish shaping the teeth, site down the length of the saw plate to make sure the teeth are aligned and aren’t filed too low.
At this point, the teeth should feel pretty sharp, but they will get sharper in the following steps.