How would you do this?

[moonmanParticipant @moonman]

Hi chaps,

I am building a PCP air rifle, something I’ve wanted to do for a while.

The main breech block requires a flat bottomed blind hole for the hammer to slide in to open the valve. The dimensions are 12mm wide by 115mm deep.

I have an idea on how I would achieve this, I’m thinking I drill it out to 11.8mm or so. I then tackle the flat bottom with a flat bottom drill and then ream it out to 12mm.

But is there a better way? I’d love to bore it but I just don’t think it’s possible over that dimension. Any imperfections in the channel will impact the hammer which will in turn cause inconsistency upon firing the rifle.

How would you tackle it?

I only have a 7×14 mini lathe so bonus points for answers that suit that machine.

[Grindstone CowboyParticipant @grindstonecowboy]

A D-bit after drilling to something fairly close to the finished size?

Rob

[Michael GilliganParticipant @michaelgilligan61133]

I know next to nothing about the construction of  PCPs but I would look at making a through-hole and then plugging it.

MichaelG.

.

Edit: __ for others who might be equally naive, this page has some exploded [!] diagrams:

https://brocock.co.uk/user-manuals/#rifle-diagrams

… in refreshingly-excellent detail *****

[Author]

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