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Making a dovetail saw: Shaping, Filing and Setting



This article is for all who wish to make a dovetail saw, but feel intimidated, and for all who need to sharpen their dovetail saws, which is everyone. Sooner or later, even the most expensive saw will need to be re-sharpened. Even touched up every now-and-then.


There are many, many forum threads and YouTube videos on sharpening plane blades and chisels, but not many articles on sharpening backsaws. Well, I would not consider myself an expert on making backsaws, having done about a dozen, but I have been sharpening my own saws for about 15 years. I consider myself a novice, which places me in touch with all others who feel a little overwhelmed by the process. I have developed a few strategies to make it all easier, and these I want to pass on. It would be great if those who are more experienced are prepared to comment, and add their advice.


I have divided this article into two sections: firstly, building the dovetail saw; secondly, sharpening and setting the teeth.


Building a Dovetail Saw


There are four components in a dovetail saw: the plate, the brass back, saw nuts, and the handle.


In this case, the 9” plate and brass back came from Isaac Smith at Blackburn Tools. The motivation for making this saw is that I was curious about a thin-plate dovetail saw. The supplied plate is 0.015” thick, and comes machine filed (i.e. not sharpened) at 16 ppi with 5 degrees of rake.


This will be a tapered plate, with 1 5/16" at the toe and 1 1/2" at the heel. Total cost $39 USD.


The saw nuts I already had, having purchased a bunch over a decade ago from Mike Wenzloff. This is the last of them.


The wood for the handle is an offcut in gorgeous flame Jarrah.


You are also going to need to drill the saw plate, and Isaac also stocks solid carbide spade drill bits. Photo later.


Isaac’s site freely offers a number of templates of handles. I chose to make my own, based on a vintage Groves dovetail saw.


Below is the template I made, showing the cut outs to aid in sawing the outline. This is a snug fit with my hand, which is 4” across the palm.






I am going to assume that everyone can get as far as sawing the outline. The first tip I will give is that it is vital that square is maintained throughout …





Secondly, mark guide lines to work to …








Only begin to fare in the curves once the final outline is completed …








As you reach the end of shaping, the mortice for the brass back needs to be cut 
before the slot for the blade. The reason I choose to do the mortice first is that it is vital that the brass back is square. It is easier to centre this, and drill out the waste using a drill press to take out the centre to depth. Leave a little to pare away for accuracy. This is the result …





Getting the blade slot square and centred is vital to keeping the plate straight. An out-of-square slot will the thin plate to its shape, and leave a curved tooth line.


In order that the slot remains square and vertical, I made a simple jig to guide the saw used to make the slot. Incidentally, the saw used – one which cut a tight kerf – was a Japanese Z-saw. Saw initially only the perimeter to a depth of 1/8”. This will then self-jig the saw blade for accuracy with deeper cuts …





The order of drilling the holes for the saw nuts is to start with a pilot hole …





… followed by countersinking the heads and split nuts …





Now you are ready to mark the positions on the saw plate …





… and drill the holes with the carbide spade bit …





Note that the drilling is done prior to any shaping. This is to maintain the maximum registration surface.


I did not take photos of gluing the plate into the brass back. This is too easy – just use Locktite. The brass back will need to have the edges eased or chamfered with a file or sander, and then polished.



Part Two – Filing and Setting the Teeth of a Dovetail Saw


We start here. On the right is the saw plate glued to the brass back. In front is a saw vise. Not least of all, as much light as you can find and a lensed visor for magnification of the tiny teeth …





The plate is inserted and clamped with about 1/8” showing above the top of the vise. This is levelled …





Why levelled? This is the first step in ensuring that the rake angle of the punched teeth are maintained exactly. I like 5-7 degrees rake for a dovetail saw.


This is the Veritas saw file holder. Modified (of course!) with a small Stanley spirit level added. The file is a 4 ½” extra slim triangular file. Vallorbe and Bahco are two available brands.


The file is inserted in the gullet, and the holder levelled …





This indicates that the rake is 6 or 7 degrees …





… on the protractor, which is marked in 5 degree increments.


The next step is to run a Sharpie along the tips of the teeth …





… and then run a mill file along the teeth. This will leave a silver tip on each tooth. Think of this like the light shining off a wire or dull edge on a plane blade. The aim of sharpening is to remove the silver tip. Doing so leaves level teeth and two intersection sides. I do this each time I sharpen a saw blade.





Filing the teeth is easy. Start at the heel end, keep the guide square and level, and push one stroke. That should be enough to sharpen each tooth.





Half on the right are done, with the other half yet to be done …





Continue until all the teeth have been sharpened. Now go back and check there are no shiny tips left. File these teeth again, if necessary. Also check the spacing of the teeth. If these is one too close to another tooth, you can “move” the tooth by filing with more pressure against the offending side.


Once all the teeth are done, it will be time to set the teeth. These are the more popular two pistol setters: Stanley #42X at the top, and Eclipse #77 at the bottom. Both work well, both may be tuned for different size teeth. Tuning involves filing the width of the hammer (the pointy bit, below).





Setting the teeth involves bending a tooth over fractionally. This increases the width of the kerf as the teeth cut, and prevents them jamming. The teeth are bent alternately, creating an equal amount of set each side of the plate. This is easier in theory, and more consistently achieved with practice.


One of the difficulties in creating set with the setter is seeing the teeth! As you move along the saw plate, setting each alternate tooth, then flipping the saw over to set the other side, you eye will glaze over, you will begin to see double, and the result will be that you lose track of what you have set. This is a problem since uneven set on each side of the plate will cause the teeth to cut inaccurately … more to one side than the other.


I have a method to make this easier to be consistent.


Take a fine Sharpie and mark each alternate tooth on one side …





Now go ahead and set the teeth on that side. Once done, wipe the ink off with alcohol, and repeat on the other side of the plate.


This method is extremely helpful with setting new teeth. Teeth which have been set previously will retain some of the past set, and you can take a cue from this. It is not always necessary to reset the teeth each time you sharpen. An indication that setting is needed is when the teeth do not cut freely, acting as if dull, or the saw binds in the cut.


Here are the sharpened and set teeth. Look closely at the tips of the teeth to see a tiny dimple where the hammer left its mark …





Before we move on it is a good idea to test the saw and see if it cuts straight. If it does not, then the set will need to be tuned. This involves using a fine diamond stone to remove some of the set on the side that is moving most. One stroke is often enough. Rather take off too little at a time than too much and have to start over. It is often also a good idea to lightly run the diamond plate along both sides to remove any set that is sticking out further on some of the teeth, and even all up.


A test cut in very hard Merbau scrap. The aim is to follow drawn lines …





This looks good – the saw kerf follows the line. And the kerf looks clean from the side (evenly set teeth leaving even marks)…





… as does the other side of the board …




The saw is done. Here are final photos …











Regards from Perth


Derek


March 2022