The horizontal plates are suspended below the level of the main plates. They hold the two balance bearings, and the upper plate also holds the escapement. The plates are sawed from 1/8" brass using Deltacad templates, as before.

It's important that the holes drilled in these plates are correctly placed. The correct placement for the holes is indicated on the Deltacad template with small dots. To ensure that the holes are drilled correctly, I use a sequence of tools.

First, I have modified a small Phillips head screwdriver to form a awl. This is made by sharpening a four-sided point on its tip, using a grinder. Basically, the tip becomes a 4-sided hand drill. This is used to make a small dimple in the dot on the plate. Using a loupe, it can be made in the exact dot. If it's off a little, the dimple can be moved a little by pressing sideways and turning the awl.

Once the small dimple is made with the screwdriver tool, it is enlarged again with a special center punch. This punch is a small, hardened punch made from 1/8" drill rod. It fits closely into a knurled nob which holds the punch exactly vertical against the work. I put the point of the center punch into the dimple made by the screwdriver tool by feel, then it is given a small tap to increase the dimple.

Finally, the dimple is enlarged a little more with an 1/8" spotting drill, which is a little drill with a very small web between the flutes. No hole is made with this drill, just a dimple. A wise toolmaker friend says that the resulting dimple should be not much larger than the web in point of the drill you intend to use to drill the hole, or the bit will pull offside when you drill the hole.

To be sure that the holes in the separate plates are in line with each other, the holes are not drilled all at once. It's a good idea to drill one pair of holes, put a pin through them and then drill more holes. If you drill all the holes in all the plates, the holes will not be in exact line with each other -- no matter how carefully you laid them out -- because drills tend to drift.

I often draw "reference circles" around holes which are a bit larger than the hole to be drilled. At the same time, I will drill holes smaller than the finished size. If the drilled hole appears out-of-center with the reference circle, it can be "moved over" with a round file, then reamed to the final size with a reamer.

The edges of the plates were worked with the 1" belt sander, as described before. Also, I used files, draw-filing until the surfaces were even and smooth.

The final finish to edges was made with fine rubberized abrasive (Cratex) points mounted in a Dremel tool. The Dremel tool is mounted in a Dremel router table, which holds the abrasive bit exactly vertical. The bit can also be run at a fairly high speed, which makes a very good fine-line finish on the edges.

With the baseplate and upper horizontal plate pinned together, I also drilled a small hole through both plates at the place where the escape wheel arbor will later be planted. This reference hole will make it easier to locate and install the escape wheel arbor at a later time.

Todays' links:

Modified screwdriver awl tip
Center punch
Awl, center punch and spotting drill
Base and top horizontal plates
Horizontal plates
Plates pinned together
Dremel router table
Polishing plate edges
Horizontal plates, Deltacad download
Horizontal plates, DXF file download