Eccentric Toolworks

“The teeth of saws are for the most part cut in the fly-press. …Two studs are used to direct the edge of the blade for the saw to the punch, at the required angle depending on the pitch or inclination of the teeth, and an adjustable stop determines the space or interval from tooth to tooth, by catching against the side of the last tooth previously made.” (Holtzapffel, Turning and Mechanical Manipulation Vol II, p 942)

This description was the only actual description of any kind that I had to work from. But of course I also had in mind what I needed a toothing gauge to do—so ultimately what I did was work backwards from what I needed, carefully considering Holtzapffel’s description as I did so. Here is what I came up with.

This first shot shows the gauge from above with some of the parts labeled. The second shot shows the gauge installed on the press.

The whole thing sits on the fly press table and is fixed to it by the bolts that pierce either end of the gauge bed. The heads of the bolts fit into T-slots in the fly press table. You’ll notice that the lefthand nut that fixes the gauge is about half the height of the one on the right. That is because I feed the saw plates from right to left, so the plates pass over that lefthand nut; it initially did stand up higher and got in the way, so I cut it down.

Probably the biggest thing you’ll notice is that my gauge has a solid fence and no studs. Holtzapffel’s description of two studs acting as a fence seemed less effective a solution than simply having a solid fence. For instance, two studs that lead the blade to the cutter would probably be placed a few inches apart in order to be an effective fence—but then once the blade was advanced to a certain point, it would no longer be supported by both studs. A solid fence, by contrast, never loses contact with the blade, and can even cross over and support the blade on both sides of the cutter.

The fence is adjustable not only for rake angle but also for depth of cut. What’s more, the same cutter can be used to cut all sizes of teeth. The size of the teeth is determined by how closely and shallowly the teeth are spaced. For the smallest teeth the old makers would have used a punch that punched several or so teeth at a time. I haven’t gotten around to making one of those yet but plan to.

The punch I did make is made from W1 tool steel. The lower die is made from O1 tool steel. The bottom die is held in place with a pair of recessed screws; they are recessed so that the saw plates can pass over them without the heads of the screws interfering. The W1 punch was filed to shape to fit the lower die and is held in an auxiliary tooling holder that fits into the fly press ram. The die and punch are made from different types of tool steel just because those were what I had on hand. The O1 is more ideal for this type of work, but the W1 works fine.

The teeth are spaced using a little indexing stop that I made from scrap steel. It is adjustable both from side to side and from front to back.

It works like the one Holtzapffel describes–it registers against the last tooth punched. That registration, combined with control of the rake and depth, is what produces good teeth. All three variables have to be regulated–if you adjust spacing without adjusting depth of cut, for instance, you wind up with all sorts of odd permutations, some of which result in the punch just nicking the blade. Like this:

Now that you see how the gauge goes together, let me show you how I use it. The first thing to do is to register the punch with the lower die. To do that I loosen the bolts that secure the gauge bed as well as the set screw that hold the punch in the ram. I move everything around until it meshes just right then gently snug it up. The punch and die are both made with relief angles so that they make contact just at the point where they shear the saw platel. Then their surfaces retreat just a bit. The punch and die either needed relief like that, or they needed to be perfectly vertical, and it was simply easier to give them a tiny amount of relief. If they sloped in the other direction they would spread apart as they engaged, and as the punch was raised you’d see that the cutting edges no longer meshed.

The next thing to do is to set up the fence and indexing stop. To do that I use a piece of saw plate that already has the desired tooth configuration–I place it against the fence and place the cutter in one of the gullets. I adjust the depth and angle of the fence so that the cutter fits perfectly in the gullet. Then I gently snug down the bolts that hold the fence.

With the plate still in place I move the tip of the indexing stop into place against the tooth beside the cutter. Basically I am aligning everything just as if it had punched the very plate I am using for alignment purposes.

I snug up the screw that holds the indexing stop, and I’m ready to go.

The pictures of actually using the press don’t look much different really than the pictures of setting it up. Only now the cutter is going up and down, and I’m not fooling around with any wrenches. Here’s a picture of just starting out punching a saw plate.

Here is the same plate much farther along.

And below is what the plate looks like with the teeth nearly, but not quite, finished.

So that’s about it. I’ve been very pleased with how the toothing gauge has performed. For me this method strikes just the right balance between thoughtfulness and expedience and seems to fit nicely with the other processes involved in making my saws. At some point down the road I will experiment with a second gauge that utilizes the two studs for a fence like the one that Holtzapffel described. I still feel that tugging at me. But for starters I wanted something that I knew would work and that I could rely on right away in my own work. Thanks for reading.