The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)

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awemawson:
OK I'm getting fed up playing with possible O ring shapes and locations, time to have an overview think.

The original idea was to drill a very long thin hole from the outside of the adaptor, and bung it's open end with a sealed grub screw thus joining the two oil ports. I'd rejected this not liking the idea of drilling that long hole with a drill that would potentially wander all over the place.

Why not do a test ?

The feature on the adaptor that needs this 6 mm diameter hole approximately 110 mm deep is only 11.7 mm wide so not a lot of wiggle room hence my concerns. I happened to have an 'unknown specification' bit of 12 mm plate, so I shaped it to the same radius as the periphery of the adaptor so as to be a true test of starting a hole on a curve, then drilled two 6 mm holes where the two oil ports are that need joining. I don't know what the plate is, but it spoilt my new M42 bandsaw blade and I reverted to the angle grinder.

Setting it up carefully with the two holes perpendicular to a set square in the vice of the Bridgeport, I then found the centre of the plate in the Y direction using my 'ball bearing edge finder'. Setting the DRO to a Y=0 datum I then chucked up a piece of ground 6 mm bar just touching the front edge of the plate, and used it by eye to find the X location of the two previously drilled 'dummy oil ports'

Then loading a 10 mm slot drill in a collet I milled a flat on the curve of the plate as a starting point, which I then centre drilled. Moment of truth now. Chucking a standard length 6 mm drill, and with much oil and pecking for swarf clearance I took it to full depth. This was still not in danger of penetrating the oil ports. Now the REAL moment of truth, in goes the long series 6 mm drill, and this is going to have to break through into both those holes. Drills tend to grab when they break though, and I know from previous use that these particular drills are quite fragile so gently does it Andrew !

First hole reached and broken through without drama, however going deeper on towards the next oil port swarf was being pushed sideways out of the previous oil port and making alarming noises and grabbing. (The long series drill, and the depth of the plate meant that I couldn't quite totally withdraw the drill for swarf clearance without removing the drill from the chuck, which I did a few times)

OK eventually the drill passed through the second oil port and I went a few mm further just to give a good edge to the hole.

Breaking down the set up and inspecting what I've done actually showed that the drill has NOT wandered significantly and probably this will be the method that I use in the final adaptor.

(Here I was just risking breaking a relatively cheap drill and a bit of scrap plate - it will be a different matter with the actual adaptor!)

modeng200023:
:clap:

tom osselton:
Well done I just watched a video on deep hole drilling last night.

RussellT:
Hi Andrew

Do you think a close fitting plug in the holes would reduce the risk of breaking the drill?

Russell

awemawson:
That's a good idea Russell so long as I can stop it rotating when the drill touches it, and also recover the bits after drilling.

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