Thread: Of Sliding Bevels, Dovetail markers & messy sheds...

About a month ago, I started a major clean-up of my shed, & hadn’t got far when I had to decide what to do with a pile of small brass scraps that I couldn’t bring myself to throw out, & started thinking of ways to use some of them up. I’ve always been easy to distract, so before long I had decided to make some sliding bevels.

SBs are not tools most of use every day, you can buy them (new or old) at quite reasonable prices, & even a cheapie can usually do the job, so you may well ask, “whatsapoint?” Well, one point is that the typical sliding bevels in circulation are made with carpentry in mind more than cabinetmaking. Stanley did, indeed make a smaller SB, but it’s as rare as feathered frogs in this country, so quite a while ago, I made myself a small version: SB sizes.jpg

I reckon I use it much more often than the ‘full-size’ Stanley it’s modelled after. So, a few small sliding bevels would be just the ticket to use some brass scraps.

I picked up the Stanley a very long time ago, for a few dollars. (The blade stamp indicates it was made between 1898 & 1903, according to this site, so it had a long life even before I got it). SB2.jpg

However, the rosewood stock doesn’t match the Bull Oak woodwork of my other squares, so I thought I’d make a new one that does. (Yeah, I know, I need to get out more!)…

A SB can be as simple as a plain wooden stock with a blade & a screw for the pivot-pin/lock, however, a bit of brass not only tarts it up, it serves some vital functions. The ‘trim strips’ under the locking lever & adjuster nut obviously protect the wood from wear & damage, but what about those bits at the bottom? Typically, as on this Stanley #25, there are two strips of brass which are through-riveted together. SB1.jpg

Now Mr. Stanley rarely added anything he didn’t consider necessary, so why go to the bother of using rivets here, when the strips under the pivot pin are simply glued in place? It eventually dawned on me that these strips are not there purely for decoration. Because the blade-slot in the stock runs perilously close to the base, there isn’t much wood left holding it together& it would be quite easy to split the stock apart if you did something silly. Riveting two brass plates over this part holds it together & minimises the chance of splitting.

I think making a SB would be a good introduction to toolmaking. You need no special gear, and all it takes is a few cents’ worth of wood & brass (so there’s little to lose if it goes wrong!). For these bevels, I used various thicknesses of brass scraps, 1/8” (3.2mm) for the tapped bit, and 1/16” and 1mm thick pieces for trim strips & blades, depending on the actual size of the SB.
On the Stanley, the ‘pivot pin’, is a loose screw retained by a hex nut on the side opposite the locking lever. SB3.jpg

It’s not a great system, things loosen over time and if you use the tool a lot, you’ll find yourself fiddling with the nut & locking lever to keep it locking in the correct position (I keep meaning to put a drop of Loctite on it). There is a reason for this seemingly clumsy arrangement, which I didn’t appreciate until I’d made a couple of these tools, & I’ll get to that later…..

I have boxes of wood scraps suitable for stocks, so it took me about a minute to dig out enough little bits for a small batch of SBs. I always think batching will speed things up, but I’m not sure it does, especially when you do it in dribs & drabs between several other jobs running concurrently! Just about any medium to dense wood will do the job, but my preference is for dense, fine-grained woods that will take a nice finish – I like my tools to be primarily functional, but I also strive to make them look decent. The stocks obviously need to be square & straight before you mark out & cut the blade slot, but no need to get too fussy at this stage, because you will be filing & sanding the brass strips flush later, which will take care of putting a fine surface on the wood. The bottom of the blade slot is usually cut at a 45 degree angle, to accommodate the angle on the end of the blade & provides a ‘stop’ when you close it up for storage.

One challenge is cutting a neat slot for the blade. This can be done either with a hand saw that makes a kerf of the right width, or a (very) thin kerf tablesaw blade, or a slitting saw if you happen to have such a thing. On this lot, I used all three methods. I have a very thin tablesaw blade that cuts a kerf very close to 1/16th of an inch, & nicely matches the 1/16th brass I used for some of the blades, a 1mm slitting saw for the small stocks where I used 1mm thick blades, and a handsaw to cut the slot for the 30 thou spring steel blades. Using a slitting saw to cut wood leaves a neat kerf, but requires great care. There is no set on these saws, & they will grab the wood at the slightest chance with the risk of damaging the workpiece (or far worse, your fingers!) I got out the slitting jig I made for saw backs, made up a simple sliding fence for it, clamped the blank stock to that, and cut the slots in my stocks without drama.

The next job is attaching the brass trim strips. There are plenty of cheap SBs around with the locking mechanism sticking up above the stock, but there are rare occasions when you need to sit the stock flat against a surface, so it’s worthwhile taking the extra little bit of trouble to get the locking mechanism out of the way, imo. I sawed out the recess for each piece, tidying up the sawn face with a file & a scraper so that the brass was a close fit.

Now, about the locking system. When I made my first SB, I thought I’d be clever and instead of using a loose screw & ‘locknut’ like the Stanley’s, I glued a thicker piece of brass on one side and tapped a thread directly into that. SB4.jpg

This way, the side remained flat, & I didn’t need a second scoop-out to accommodate the nut. But I’d failed to grasp the reason for the ‘loose’ pin. It is desirable to have the locking lever-nut tighten within the edges of the stock, otherwise it will get in the way when you use the tool as intended. I thought I would be able to adjust the locking point by screwing the pivot pin back & forth a bit. I was quite annoyed when I discovered that no matter how much I turned the screw in or out, the locking nut always tightened in the same place. After thinking long & hard, the penny finally dropped. ‘Of course’, you say, ‘the thread helix will always enter the surface at the same point of the clock, you dope’. Turning the screw does not alter this, so it won’t change where the nut tightens, one jot. The solution is to file/sand a little off the bottom of the nut so the thread of the nut starts at a different point. Once I realised this, it wasn’t too difficult to adjust my locking levers to tighten where I wanted them to, by filing/sanding a bit off them. With the ‘loose’ pin method as on the Stanley, you use the nut opposite the locking lever to move the position of the screw without rotating it, which does change the point at which the thread helix enters the surface. It’s six of one & half a dozen of the other, I suppose, making a flush, fixed nut is a bit neater, imo, & slightly easier, but the extra work of fitting the loose screw makes final adjustment easier. You decide which suits you better.

With the brass pieces glued in place (with Araldite), rivets were added through the bottom strips & peened into small counter-sinks (for rivet stock, I used some 2mm brass rod from McJings, which peened very nicely). Then the peened heads can be filed & sanded flush. Here are the various stages of the process. Stanley used 2 rivets, but I used 4 for extra insurance: SB5.jpg

The finger groove in the larger stock was done on a makeshift router table with a coving bit & a couple of clamps on the fence to act as stops & keep the groove even on both sides. In common with all the Casuarinas I’ve met, Bull-oak is highly susceptible to friction-burns, & despite being careful, I got scorch marks at both ends of my grooves. These were removed with a scratch stock (in retrospect, I should’ve used it for the whole job & left the screamin’ demon in the cupboard! ). SB6.jpg

Preparing the blades is straightforward. I hacksawed out the rough shape from the brass bar (or used a 1mm cutoff wheel in an angle-grinder for the steel), then straightened them up with files & paper. I drilled a hole at each end for the slot, & joined them either with a jewellers’ saw or the cutoff wheel . Unless you only ever use one side of your blade, it’s important to get the edges parallel, & that may take a bit of fiddling with files & paper. I got mine to within <0.04mm (~0. 0015”) maximum deviation without too much trouble, & you could probably do better if you are the obsessive type, but that is quite close enough for 99.9% of woodworking.
The lever nuts were cut out of bits of 3/16” bar (or 1/8” for the smallest gauges), with a jewellers saw, cleaned up with files & sandpaper & polished: SB7.jpg

So, with locking levers adjusted & a bit of spit & polish, this lot is good to go: SB8.jpg

The woods, L to R, are: Bull oak (Allocasuarina leuhmanii), Hairy oak (Allocasuarina inophloia), Hairy oak again, Bull oak, Western Rosewwood (Acacia rhodoxylon), & HO again.

But there's more....