Thursday, 22 May 2014

Hand saw sharpening: Be brave, save money and discover just how easy it really is!

When I was a small boy, my father had a handsaw, which was my grandfathers. It sat in the shed and rarely got any use. Not because my father was not the sort of person to build things or use tools... Completely the opposite, he would spend hours tinkering and building model steam engines from etched brass and white metal, as an apprentice on the railways he has a massive skill set for metal work and engineering.
The handsaw was blunt, "this could really do with a good sharpening" he would say, on the odd occasion it would get used.


I have always been in awe of people who use old hand tools for woodworking, and although I have a small(ish) collection of old tools that periodically increases, I have never really been one to look at saws. I just buy a disposable hardpoint saw from my supplier, and use it until it's blunt.

But ages ago I got my hands on two beautiful old tenon saws, which were already pretty sharp, and they are great, you've possibly seen my favourite one, a little dovetail saw lurking in the background to most, if not all of my YouTube videos. It's great for trimming off a little bit here and there. But this use has taken it's toll on the teeth which finally let me know that they require sharpening!

A little daunted, I decided to research saw sharpening a little, and found the Paul sellers video, (which is great!) Armed with this new-found knowledge, and some confidence I broke out my saw file, and eclipse saw set, and got to work.


A Simple baton with a saw kerf along most of it's length, drilled at the end to stop splitting provides enough support for filing the teeth.


I started off cutting down a scrap piece of softwood to about an inch square and marked the centre-line on one face. Then drilled a 1/4" hole at a point on the centre line, about 2" from one end. next I simple took a saw and cut through the baton along this centre-line mark, up to hole. By sliding the saw blade into this baton, which now look like a giant square Victorian clothes peg, I can clamp the whole lot in my vice with the teeth just about 3/16" proud of the top. Giving the saw blade ample support for the filing of the teeth.


Keeping the teeth slight proud when clamped in the vice ready give ample support for filing.


The next step, which is effectively the first step in sharpening is to run a flat file across the top of all the teeth. A seemingly counter-intuitive measure you might think, but it actually serves two key purposes. I used a single cut, bastard file.
Firstly, by running the file length-ways along the saw,  the file ensures that the tip of each tooth is at the same height as the rest. The second reason, in my opinion, is slightly more practical. By filing the tips of the teeth you expose fresh metal, which due to it's shinny colour creates a very visible indication of what you'e doing, and where to put the file. 
At this point I also worked out the current tpi (teeth per inch) of the saw, which was 16tpi. I next marked points at the end of the saw, and at the 1" and 2" points from the tip of the blade.


 

A light pass with a flat file flattens the teeth to the same height and indicates which parts of the teeth require the most attention with the saw file.


I wanted to sharpen the teeth to a progressive cut, Tenon saws typically are sharpened with a Rip-Cut" tooth pattern, so  by changing the angle of the teeth along the blade the nature of the cut can be altered so that the teeth at the toe, where the cut is started is a less aggressive and easier cut, where as the teeth after 2" are the aggressive pattern of a traditional rip cut. the first inch of teeth got 2 passes with the saw file. the orientation of the file is square to the blade vertically and length-ways. The top of the file is flat, meaning the teeth being sharpened are less aggressive on the wood and easier to start a cut.


For the rip cut patter the file is held square to the saw blade, both vertically and lengthwise.


After the first inch of blade I wanted the teeth to be slightly more aggressive in nature, this was achieved by rotating the file forward slightly and keeping the file in the same orientation as before - square to the blade. The key, I found when sharpening, is to keep every aspect consistent for each tooth. This boils down to the same amount of pressure on the file for each stroke, and the same amount of travel, (i.e. the number of strokes) - I used two light strokes per tooth. You really don't need to put a huge amount of pressure on the file.



A couple of light strokes of the file should be enough to create a sharp tip on the teeth.


After the first 2" of blade I changed the orientation of the file once more. Rotating forward sill a little further so that the back edge of the file was vertical. This makes for the most aggressive tooth pattern, placed further back on the blade, where the majority of sawing takes place. all teeth on the blade from the 2" point are cut to this same angle.

With the file orientated so that the back is vertical, this aggressive tooth pattern is great for rip sawing


Once each tooth had been filed, a quick check along the side of the saw soon shows up any inconsistencies of low points, these can easily be rectified with a quick half stroke of the file on each side of the tooth. you can also see the progression of the aggressiveness of this tooth pattern.


Progressively increasing in aggressiveness means cuts are easier to start with the tip of the blade.

Once each tooth is sharp they then need to be set. This gives the saw it's kerf size. The tool of choice is a saw set. A simple pistol grip type tool, with a hammer and anvil used to push the individual teeth over to the side. This type of set can be adjusted from a coarse,  4 tpi  up to the finer dovetail saws with as many as 30 or so teeth per inch. 


A simple mechanical tool, the saw set is easy to use.

With the saw blade adjusted in the vice, it's  time for the last stage of sharpening, to set the teeth. By starting at one end of the blade each tooth is pushed to opposing sides, odd numbers one way, even numbers to the other. I actually found this marginally more challenging than filing the teeth, as it's down to careful movement to make sure you push the right teeth in the right direction. Slow and steady concentration is the key to this stage.

Concentration is the key for setting the teeth.


I found sharpening two hand saws to be quite enjoyable, OK, so they were only small ones, and the tooth pattern is pretty simple, no fleam angles to worry or think about. But it's given me two things, confidence and some experience. Furthermore, i't given me the opportunity to save more money further down the line.
Saw sharpening is not a complicated task, but it takes skill and experience to master - something I'm yet to attain, but won't unless I practice. It takes only a few simple tools to sharpen a saw (well a tenon saw at least) but I say, In for a penny, in for a pound!


Saw sharpening takes more practice than it does tools.


I'll definitely be sharpening my own saws now. why not?! Maybe my youngster will ask me about using such an old saw one day, and I can say "I'll use that one, I know it's sharp, because I sharpened it!

View also my YouTube Video on this saw sharpening. It shows a little more detail, and really serves to compliment this article.
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