Dovetailing Infill Planes (Part I)
To many people the British style infill plane symbolizes the epitome of high class plane making. The 19th century hand planes manufactured by Stewart Spiers, Thomas Norris and others are coveted and prized by collectors and users alike for their workmanship, their beauty, their solidness and their overall usefulness around the workshop - and with their bronze lever caps, rosewood infills and, often, dovetailed construction it's not hard to see why there would be so much interest in them. Although the dovetailed versions cost more to buy than their cast infill companions, the advantage of having a "shell" that was impervious to cracking should the plane be accidently dropped was a bonus well worth paying extra for.
A lot of woodworkers feel that making a dovetailed plane is just too difficult a job to even attempt, and that the skills required have to be honed and developed over many long years - with more than a few dovetailed failures along the way. It's probably true to say that that's what some of the infill plane makers would have you believe as well! After all, they would much prefer for you to buy a dovetailed hand plane from them rather than attempt to make one yourself. And, to be honest, the planes they make and sell will generally be of a much higher standard than the first one or two that you make....but this is not a hard and fast rule. With care, you could make a dovetailed hand plane which is every bit as good - if not better - than one you can buy from a specialized maker.
Some people feel that there's a lot of mystery surrounding metal dovetails and how to make them. The truth of the matter though is that basically anyone who can make a dovetail in wood can also make one in steel, bronze or brass. In fact in some ways it's easier in metal than it is in wood - it just takes a bit longer because the material is harder. This actually helps, rather than hinders, you because it takes a little more effort and time to mess it up. When things are going slowly you have more time to check the work as you go - or at least in theory you do. Even if you do file away a bit too much from one dovetail you can usually "coax" the metal around it to fill it in again. Try doing that with a wooden dovetail!
It's often the "double locking" part that stumps most people. After all how do you get the dovetails together in the first place if they're dovetailed in both directions? The simple answer is that you assemble one dovetail, then lock the other dovetail down afterwards by peening the metal over. Until this is done the dovetails are free to slide and interlock whenever you want them to - just as wooden dovetails are.
I always try to advise people to start out their infill plane making by knocking together a small plane. Why a small plane though rather than, say, a full sized smoother? The answer is simple. It's easier and more encouraging, I feel, to get some early successes on the board, rather than invest a lot of time and effort on a larger plane. The basic skills required are the same on both planes, but a smaller plane is quicker to make and has less dovetails to cut and peen. It's not difficult for even a beginner to make the dovetailed shell of a small metal plane in a day - or even just a morning. Another bonus is that, because you use a lot less material on a small plane rather than a larger plane, it's much cheaper to make.
While it could be argued that a first-timer should practice dovetailing on a few pieces of scrap metal I feel that you might just as well try to make a small plane. That way instead of having dovetailed scrap metal kicking around the workshop afterwards you have something a little more useful. If things don't quite work out the way you hoped they would then you'll appreciate that you learned on a smaller plane rather than a larger, and materially more expensive, one.
Not that failure is a bad thing necessarilly. On the contrary, there's an awful lot that you can learn from a failure. The problem is that when things aren't quite working out, many people tend to put the project aside and not work on it again. Even worse, they throw it away. This is not a good thing. Even if you do happen to create a "dovetail monstrosity" there's a good chance that it can be fixed up and made into a serviceable plane at a later stage, when your plane making skills are a lot more finely tuned.
Because we're making a small plane there is really only one or two "special" things we need in particular. The first is a set of machinists' needle files. Don't worry about the larger set with only 5 or 6 files in it - they do have their use, but just not for now. Look for the small set with about 14 or 15 different files in it. They don't need to be an expensive set, but they do need to do the job. I'd have to say that, to me, needle files are the one exception to the rule that you should buy the best tools possible. Instead, what I do is buy a set of cheap needle files, test them out on a variety of metals to make sure they're up to the job, and then go back to the store and buy several more packets of the same brand and batch of files. Why? Because needle files are more like sandpaper than they are like other tools. There's simply no need to buy a $100 set of needle files when 5 sets at $4 each will do exactly the same job. To my mind the only reason to buy expensive quality needle files is if you're making jewelry, where the finish of the cut is much more important. In plane making the finish isn't an issue as you're hammering the heck out of the metal joint anyway.
The second specialty tool we need is an automobile points file (or two or three). These are just small, thin files used to clean up the electrical points on the cars distributor or on spark plugs. After a bit of modification these are great for working on very small plane mouths. Unlike your needle files, try to get a good brand wherever possible, as even the good brands are fairly cheap.
Now for the modifications.... With the points file you'll notice that it has teeth on both its faces. Use a grindstone or a belt sander and carefully grind one of the faces clean and free of teeth. This gives you a safe edge and ensures that you won't accidently mar any surface that you don't want to. This is especially important for ultra fine mouths such as the ones on miter and shoulder planes.
In your packet of needle files you'll find many different shapes, some of which are much more useful than others. One of the most useful shapes is called a "barrette", and you should really check out the packet to make sure it has one before buying the set. The barrette is basically a "squashed down" 3-sided file, but with 2 of the sides clean and free of teeth. To make this file even more useful for making small dovetailed planes you can, once again, grind the back of the file so that the end is thinner and easier to get into tight corners. Grind carefully and be careful not to draw the temper of the file though, and also be equally careful as you use the file, as the thin edge is very brittle. When the file is thus modified though it's more like a paring knife (almost) than a file, and great for getting nice sharp corners.
Once your files have been modified, mark out your dovetails just as you would do if you were using timber. It doesn't matter if you're using steel or brass or bronze for your first plane. You could even use aluminum if you wanted to. Just make sure that the metal is about 1/8" or so thick as any thicker on a such a small plane is unnecessary.
First, score a depth mark of the required thickness, but be sure to allow about 1/16" extra in both the sole and the sides as you'll need this extra material to peen down and lock in your dovetails. You can add a bit more if you want, but no less - not for a first up plane anyway. Sure, more material will mean a bit more cleaning up at the end but, in the scheme of things, it's not too bad - especially on a small plane.
The angle of the dovetails is not that important - whatever ratio you have for your dovetail gauge will do. If the dovetails are too sharp an angle though it makes it a little more difficult to fill in the corners.
If you're unsure about cutting a mouth in a one-piece sole, or you want a plane with a lower bed angle such as a miter, then you can cut your sole plate in two and use one of the tails on the sides of the plane to "cover up" the ends of the mouth. Don't forget to make allowances for the bed angle as the dovetail here may have to be wider than the others on your plane. Experiment a little to get a look that you're comfortable with.
Once you've marked your dovetails, clamp each piece up in a metalworking vice and remove the waste material with a hacksaw, by drilling or just filling it away. One quick way to remove the waste is by slotting it with a hacksaw to just above the depth line, then using a rough bastard file to remove the leftover waste material. Don't worry at this stage about following the profiles of the dovetails, as it's better to file these to shape rather than cut them. Also, be careful not to go over any of the lines, and make sure that you are cutting the waste, rather than the pins and tails.
I should add that most times I will stack both sides of the plane together in a vice and remove the waste simultaneously. I also cut the plane's profile beforehand, but file the dovetails to size individually, one side at a time.
Once most of the waste material has gone you can now start to "refine" your dovetails. Go slowly and keep checking all the time. Ideally you want the fit to be as accurate as you can make it, but don't panic if it's a little loose - once you start peening it'll soon lock up tight on you. File each pin and tail one at a time and use the previous ones as a guide to help locate the next.
Once all of the dovetails are cut and filed to a nice fit you can now file the secondary bevels on the sides of the plane only that will lock all three of the plates together. This is where you really need your modified burette file handy as the corners of the tails need to be nice and as sharp looking as possible.
On the issue of the secondary bevels it should be said that you don't really need to have deep bevels at all. Just enough to make the assembly "tight". In fact if you can taper them from a wide bevel at the outside edge to an almost non existent bevel at the corners then filling them in is much easier. You don't need to push the metal into the corners as much. Having said that, the secondary bevels on the dovetails in the photographs are constant all the way, but they don't need to be.
NEXT: Peening dovetails
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