The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
awemawson:
I did have a 'heart in the mouth' experience this morning :bugeye:
I decided to set the spindle running at low revs - 100 rpm just for a first visual check - and it was immediately obvious that something wasn't right. There was a distinct eccentricity of the outer nose where the A2-5 taper will be turned.
Now a few microns of run out at this stage is no issue as the next stage is to use the lathe to turn the next taper, but NOT something that I can see with the naked eye!
Running a feeler gauge around the interface between the spindle nose and the adaptor flange revealed an uneven gap. All 6 M12 bolts good and tight so what's happening. I thought perhaps the 'drive peg' hole wasn't deep enough and it was bottoming.
Unbolting the problem was fairly quickly found - the 6 retaining bolts were very marginally too long and had bottomed in the tapped holes in the spindle, and weren't actually pulling the flange tight onto the spindle :bang:
It was a matter of a few minutes to replace the bolts with shorter ones, and phew - all now looks fine :clap:
A big manual lathe tidy up now and I need to work out how to program the Beaver to give me the 7.125 degree taper in a progressive manner so that again I can creep up on a snug fit and yet be able to see what's happening. (The tool turret gets in the way of visual checks)
awemawson:
OK Colchester Master 2500 returned to normality after a rigorous clean up and replacement of 3 jaw chuck.
And while this was happening I powered the Crocell pot up so that I could preserve the Taper Test Gauge. After all it took ages to make, might as well look after it, although frankly it's unlikely that I'll use it again.
mattinker:
If you preserve it it shouldn't be needed again except now I've jinxed it by saying that! Sorry!!! Cheers!!
awemawson:
This mornings task - sort out where the O ring seats had been compromised by through drilling the 8.5 mm holes for tapping the A2-5 mounting flange.
First I had to return the O rings seats to their design depth of 2 mm - this had been made shallower by adjusting the taper to fit the gauge. Manual mill, hydraulic ports located by dropping a 6 mm drill into them - 1/2" end mill inserted into collet and depth adjusted accordingly.
Then I turned up some 8.5 mm rod with the tolerance on the fat size, cut a pair of 6 mm long 'pills' to act as inserts, popped them in with Loctite 601 high strength retainer and adjusted their depth with screws coming in from the A2-6 side.
The insert very slightly impinges on the recess for the O ring but I don't think that it is of any consequence (famous last words!)
Can't do much more until the 601 has cured - probably just as well as I have duties with cottage guests arriving.
awemawson:
The 601 has had a couple of hours to go off - it's supposedly OK after 25 minutes. So I've put O rings on the adaptor and re-fitted it to the spindle - I want to check what sort of squash they take up - I'll leave them over night and examine them tomorrow.
Meanwhile I needed to work out what tool to use to be able to 'get at' the A2-5 taper to machine it. It's well inside the protected zone being 'behind the chuck' so to avoid mucking about with the settings for the 'machining envelope' I'd got hold of a humongous through coolant boring bar with a 32 mm shank. Mounting it up I proved that I could reach all aspects of the taper so next thing to check is the through coolant.
The bar is hollow with a small passageway for coolant. The holder accommodates this and also external coolant through a pipe mounted in a ball socket that can be locked in any position by tightening a countersunk cap head screw that bears on the ball. To redirect the flow down the hollow all I have done is to rotate the ball so that the hole for the pipe is at 90 degrees to where it should be to block the port, it's not 100% but adequate for what I'm doing.
The bar is really sticking out too far but I need it's length to to maintain visibility and I don't want to cut it down as that is the only way of reducing it's projection. (Shorter bar = less chatter but it's pretty solid!)
So two thing left to do, both of which I'm nervous of:
A/ programming the taper so that I can advance it in nibbles for test fits
B/ Drilling those long linking holes to couple the hydraulic ports
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