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

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Henning:
Not having worked on a CNC machine since the days you had to code everything on the machine I’m probably totally out of tune, but would it be possible to mock up something like a lathe steady rest for the tool? Would probably need some creative programming to ensure no crashes perhaps Anyways, quite enjoying the saga, and all the detours. Keep up the great work

awemawson:
Nice idea Henning, but on a CNC lathe the bedways are not accessible to put things like steady rests on sadly. Hopefully a stubby boring bar will triumph.

Today I decided to tackle the setting up to drill those rather long oil galleries. The ports to join are on either face of the adaptor and need to be aligned precisely vertically. I reasoned that by inserting a 6 mm bar into each port I could somehow rotate the adaptor while mounted on an angle plate until they were aligned, then worry about lateral positioning.

(I need to drill 6 mm galleries through a land that is only 9.8 mm wide for practically the fully length of a long series drill)

It rapidly became obvious that having the adaptor held on the angle plate with a central bolt wasn't going to work. Adjustment in small increments was by rotation of the adaptor, BUT the centre of rotation kept changing as the bolt was a very loose fit.

What I needed was a close fitting pivot to rotate the adaptor on in a more controlled manner. (I'd considered a vertically mounted rotary table but one of the ports would have been obscured by the table).

Hunting through the scrap box, to my delight I found an old tractor hitch pin that was absolutely precisely the right diameter and it also was centrally drilled for a grease way which would aid drilling and tapping to put studs in the ends. Ah yes - BUT it's as hard as a witches titty. I did cut the bruised end off with an angle grinder but facing it on the lathe with carbide tooling was hard work and tapping it with HSS taps would court disaster. OK shove it in the forge and soften it ! Well common sense prevailed - it is full of grease in the central hole so it'll smoke the place out, and the fire will mar the currently acceptable finish.

Don't be a cheap skate I said to myself as I cut 100 mm off the end of my rapidly reducing stock of 50 mm round EN8. I turned it to a close fit for the bore of the adaptor (43.450 mm) and drilled and tapped both ends M12 having parted it of at 57 mm long to let it clamp in the 60 mm deep adaptor bore.

This pivot piece then bolted onto the face of the angle plate allowing smooth rotation with the centre of rotation staying put, unlike previously.

Next stage - do the adjustment, but I've been called away for the present.

awemawson:
Now having the proper pivot, rotating the adaptor into alignment was far easier.

I had to modify the angle plate to allow the 6 mm bar into the lower hydraulic port, but that was just a quick trim with a carbide burr in the die grinder.

So having the two ports hopefully 'dead nuts' in alignment vertically, I picked up the edge of the flange with my 22 mm bearing edge finder, popped over (11 + 4.9) mm and set the X zero and was ready for drilling.

First up, a 6 mm end mill to start the hole as starting a drill on a curve would be impossible. Then when down about 20 mm, with copious amounts of lubrication and chip withdrawal I swapped over to a jobber length HSS Cobalt drill and gently took it to full depth. I continued to use the collet as it gave much more headroom than a chuck.

Then for the 'Long Series' as this is a deep hole. I only have HSS not HSS Cobalt - initially it went fine but then DISASTER my worse fears - the drill broke.

So I have 50 mm of 6 mm HSS drill broken off with it's tip about 60 mm from the surface - stuck firmly and not going anywhere :bang:

Fortunately it looks that there is enough clear hole to give me an accurate start for an EDM electrode if I can find some 6 mm thin wall brass tube, and it's already mounted on the angle plate in the correct attitude.

. . . .oh joy . . .

awemawson:
Well I found some 5 mm copper electrode tube - there won't be much of a 6 mm drill when it swallows a 5 mm electrode!

Daren't leave it alone so it may be a late supper.

awemawson:
I gave up last night, it was just taking toooo long. I had to remove the electrode tube as the machine has a habit of lowering it's head when the hydraulic pump isn't powered with the result that thin tubes get bent. This had the consequence today when I refitted it that it wasn't quite revolving true, but only a fraction. This messes up the servo feedback system as it keeps feeding and withdrawing as the electrode lightly brushes the wall of the existing hole. In the end I inhibited rotation, which I'd initially enabled due to the rather uneven broken drill end. But we were well past the drill at this stage and in virgin metal.

I'd decided to finish the hole with EDM rather than drilling, as the surface of an EDM'd part has been subjected to intense heat at a microscopic level, and with this alloy steel could well cause hardening that would break another drill.

When it finally broke through into the lower port I breathed a large sigh of relief, as not only was this particular disaster overcome, but the holes actually lined up :clap:

Next job was to re-mount it on the milling machine, drill the upper port slightly deeper (5 mm) to intersect the long hole and then re-mount it to open up the top of the long galley to 6.8 mm and tap M8 to receive a grub screw to blank it off.

I went very gingerly and used an HSS Cobalt drill. Started the tap in the mill to guarantee verticallity and finished it by hand.

So after a lot of faffing about that is one of the two oil galleries created. I have ordered up HSS cobalt 6 mm long series drills for the next one, and also some 6 mm thin wall brass tube in case I have another disaster!

(I might tidy that rather ragged tapped hole up with an end mill)

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