December 9, 2023

Tapping the 160

In order to gain more reliability I decided to add a perry pump (VP-30) to the O.S 1.60 FX in the red Laser. I thought tapping a hole inthe backplate would be easy but the way this bugger is cast I was at a loss about how to proceed. The cast-metal backplate is so thin that it would not be possible to tap it in the normal manner, plus the supports and the tunnel in the backplate, which serves no apparent purpose other than to puzzle me, left me little options. 

So here’s what I did:

I drilled the hole all the way through, enlarging it to 7mm and then tapped it to 8mm (Veeeery carefully!). Then I cut an 8mm bolt, drilled it and tapped that to 3mm to fit a pressure tap. Then I screwed the whole assembly into the 8mm hole. Note that I did not tap it to 8mm all the way in, so that the 8mm screw can be tightened properly and will not screw itself out. A lot of luck ensured that I tapped as fas as the screw was long so that the fit is flush with the backplate tunnel. I turned out very sweet!

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