johnsmachines

The 1779 model naval cannon is complete, finished!

Photos of finished project in next blog.

The last task was to make the bolts, hinge and keys which hold the barrel to the carriage.

These small items took 2 days to make, demonstrating that the size of parts has no relation to the the time taken to make, except in an inverse relationship.  ie. the smaller the part, the harder and longer it takes to, make it.

The bolts which hold the barrel trunnion to the carriage have small rectangular holes which hold a key.  The holes are 2.4mm wide and 3.6mm high.  That is smaller than my smallest file.  My smallest endmill is 2.38mm diameter, so that determined the size of the rectangular holes.

I drilled the holes with the endmill, then elongated the round hole to a rectangle by filing.

The problem was that my smallest file was a square file 3x3mm.

Solution!  I ground the teeth off two surfaces of the file, leaving 2 faces 2.4mm apart, and 2 cutting faces 3mm apart.  (using a surface grinder).

Finished rectangular hole on right.  FIling in progress on LHS.  The head of the bolt was silver soldered to the shaft.  Second soldering effort worked.

Then I had to make the keys. These are truly minute!

So I cheated.  I CNC’d the shape on the end of a piece of brass rod, then parted off the keys in the lathe.

Parting the first key.

That key is 9mm long and 6mm high.  It still needed some filing, which I accomplished in this tiny toolmakers’ Starrett vice.  That file is 3x3mm.