I began to get requests for dovetail markers after I made this one in brass and Tasmanian Blackwood infill:
This is a little joke .. a play on itself since it was a dovetailed dovetail marker.
So I came up with what I thought was a easier to build, cheaper but still desirable alternative … an all-brass marker.
Below
I shall demonstrate how I make these brass dovetail markers. They
appear to be a very simple construction (and they are), but they are
also very time consuming to make ... too time consuming at this stage
to make more than the ones I have already promised to make (they
have, in fact, all been completed).
How much time? Well I
would estimate about 2 hours a piece. I have not put a clock on it,
so it could even be longer. Why so long? Because they are more
complicated that one realizes. In effect, one is shaping in 3D ...
All angles must be precisely correct. But … adjust one angle
slightly, and others need then to be corrected as well.
I
need to develop a more time-efficient way to do this ... templates???
Here we go ..
Step 1 - I am using a length of 32mm (1
17/64") wide and 3mm (1/8") thick brass angle. Here I mark
off widths with a saddle square. I am aiming for a final width of
about 3/4", and to get this I will lose about 1/8" in
"adjustments. 
Step
2 - Mark off the dovetails. These are in ratios of 1:5, 1:6, 1:7, and
1:8 
My
dovetail saw ! 
Step
3 - cut the sections square. 
Step
4 - Remove most of the waste with the hacksaw. 
Step
5 - Remove the remaining waste at the disk sander. 
Step
6 - Now fine tune with sandpaper and files. 
Measure
the angles constantly.
Once the shape is true, I clean up all
surfaces by lapping on 240 grit sandpaper, then use a fine deburring
wheel. The latter leaves a smooth, very finely matte finish.
The
next step is to bevel all outer edges with a file, and the final step
is to stamp the ratio on the top of the gauge.
Here are some
images ... 
Where
is the complication? Well, as I noted earlier, this guage is 3D. It
is not simple L-shaped. The front "dovetail" is angled,
plus the rear section is a 90 degree square. Of these angles, the 90
degree square is actually the more important one (your cuts across
the board will determine whether all mates accurately). The angled
front must transition smoothly into the rear square. To do this I
have continued the dovetail angle into the square, so it creates an
chamfer all the way up and around the sides.
You may see this
more clearly here: 
Now
if I have to re-shape a dovetail angle and, say, it moves inward by
.5 degree, it will move the square inward by 1mm. Similarly, if the
rear square is off by 1 degree at the rear side, squaring it means
having to re-file the dovetail to which it connects. Get this wrong
and back you go again! It is just amazing how quickly a piece that
starts off at 22 mm wide ends up at 19mm (3/4"), that is, will
lose a 1/8" in width. The problem is that it can do this so
quickly that it is easy to drop below 3/4", and I will reject
all those gauges as too small.
The job would be so much
easier if the initial machining process created the perfect angles
straight off. Easy enough on a milling machine, but I only have the
tools you see above.
Simple bugger, isn't it!
Regards
from Perth
Derek
May 2008