Engine Turning or 'Spotting' the 4 Bore Locks.

Even a small and perhaps relatively straight forward job like spotting the detachable locks becomes a bigger task when we move up to the 4 bore. This is work that requires a keen eye combined with patience. In normal circumstances, Jason will be sitting at a pillar drill with the lock components in a jig, he will carefully bounce the lapping paste on the lock plates whilst indexing the jig to move to the next spot. Getting the perfect alignment of spots is not an easy task I assure you, a small run off in direction becomes very noticeable and when that happens it is a polish off and start again situation.

With the size of the 4g lock plates being too large for the pillar drill, the next stop is the Bridgeport Miller where the lock plate is set up with the scaled up size 'spotting stick'. Lining up and indexing the head on the digital read out is the method on this larger machine, the digital read out takes over from the eye. Bigger locks, bigger machine and more time on the job.

The pair of 4 bore guns have extra locks to each gun, a total of four pairs of locks which will take Jason about 60 hours of careful work to get perfectly finished.

The spinning stylus covered with lapping paste creates the polished circles. These are overlapped to create the desired finish effect.

The 4g Lock alongside a 12g Lock

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Comments

1 comment

L

Larryon November 04, 2025

Larry on August 4, 2015 at 5:34 pm

That is a really great order you have. I’m looking forward to seeing photos from the client of the game he has taken with this gun… presumably something along the lines of dove! And, as always, the jeweling (as we call it in the states) on that lock is impeccable.