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

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awemawson:
It was at this stage that I dug out my 'soft jaw clamping fixture' that I had bought for similar service on the Traub lathe, only to find it was dinky compared to what was needed. I had been sure that it would work, but the difference between a 10" and a 6" chuck is rather a lot !

So what to do :scratch: I could make something up for this one size, but this is going to be an ongoing requirement as jaws are changed in the future. Better to bite the bullet and get the right thing. A bit of ringing around for best price set the dealers into a flutter, as behind the scene it turns out that they were ringing each other to see who had stock. Rotagrip won the day, and then minutes after I placed the order Cromwell Tools rang me back to say that their supplier had just sold their last one, and they were now on 8 weeks delivery. Yes says I, I just bought it :lol:

Excellent next day delivery, so the clamp ring arrived this morning by Adrian with ParcelForce.

Now the theory is that you adjust the ring to such a size that the hydraulic chuck jaws bear down on it via pegs that go into the counter bores for the jaw mounting screws and it ends up clamped with a bit of 'meat' for you to bore out with a boring bar. It's actually quite a job juggling it, holding it in place, and operating the 'chuck close' button that is a fair distance away from the chuck.

It was at this stage I found that as these were new jaws and still fairly long, the clamping ring at its extreme would not clamp :bang:

A bit of head scratching showed that as the clamp pegs are 18.5 mm and the chuck jaw counterbores are 25 mm, the slack was the problem. Quick solution, turn up some collars to slip over the pegs and sure enough we now have the correct travel to clamp, but we also have a pile of bits to hold in place at once while pressing that button, arm outstretched. Flying to my aid came some rare earth magnets, that not only held the collars on, but nicely held the clamp ring against the chuck jaws :clap:

awemawson:
So at long last boring could commence :thumbup:

I'd turned up a plug gauge on the manual lathe with 24.5 and 25 mm diameters, as this boring was going to have to be done the old fashioned way - cut - measure - cut again. (The boring bar hasn't been measured and put in the tool offset table yet!)

So, cut a bit, measure, cut again measure with the bore gauge, get a finish depth of cut a whip it off. I used the jog facility and MPG rather than a program as the tool disk gets rather close to the chuck jaws as I wanted to minimise tool overhang.

. . . so what should have taken a couple of hours took a couple of days !

awemawson:
Some of you may recall that I went to great efforts to mount a Renishaw MP12 probe, only to find that it's optics looked in the wrong direction being intended for a milling machine not a lathe.

I did an experiment with transmission through glass that proved that the IR wavelength used would pass, so ordered some prisms off eBay that have been on a slow boat from China, hoping to turn the beam through 90 degrees.

Well the boat has docked at last and would actually appear to have come from Malaysia. I had ordered four prisms, knowing that two would when joined cover the width of the optical window in the probe, and the others could be spares. Just as well, as two of them were chipped. Frankly unlikely to affect the passage of the IR much, just unsightly.

So experimenting with the two chipped ones - not worth sending them back at the price they were(n't) - I super-glued them together with the smallest drop that I could decant, then fixed them temporarily to the MP12 with a tiny dab of hot melt glue that will be easy to remove without damage to the probe.

Lo and behold - they WORK :clap: Now I just need to devise a more robust method of retaining them on the MP12 probe that looks less crude than the experimental set up - but definitely a success :thumbup:

nrml:
A sung fitting 3D printed sleeve to go around the probe with a suitable mounting point for the prisms would do the trick.

AdeV:

--- Quote from: awemawson on June 11, 2019, 06:48:38 AM ---Lo and behold - they WORK :clap: Now I just need to devise a more robust method of retaining them on the MP12 probe that looks less crude than the experimental set up - but definitely a success :thumbup:

--- End quote ---

Something vacuum formed, perhaps? :D

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