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

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awemawson:
Tom, that's just a bit of code I knocked up to try it. In real life action you could probe a few times and take an average of your readings if you wished, but this was just to prove to my own satisfaction that I understood the @720 and @371 functions - their description in the Siemens documents is not exactly flowing with detail!

It doesn't help either that the two probes are numbered 0 & 1 in one function (@371) and 1 & 2 in another (@720) - nothing like having a bit of consistency :clap:

awemawson:
So at long last I'm in a position to try and make a VDI40 dedicated mounting for my Renishaw MP12 probe.

Apart from the time to do it the hold up has been deciding how to make the actual VDI40 spigot that has the rack teeth that engage with the locking mechanism. I know from when I 3D printed some blanking plugs that the 'phasing' of the teeth is quite critical.

Having worked out a way, an odd shaped VDI tool that looked like it could be a 'doner' cropped up on ebay which I won for the princely sum of £4. I had expected to have to soften it by annealing before I could work on it, but it turns out it is a custom made item using a commercial 'soft blank' where the VDI40 bit is hard, but the rest is still soft(ish). Well that saved digging out the annealing furnace :thumbup:

So today I found a bit of time to make a start. The blank is far too long so how to lop a bit off - looking at it I reckoned probably at least two parting tool tips were it done on the lathe, so I used the Band saw with a bit of ingenuity in the clamping - went quite well and wasn't all that slow considering it's 85 mm in diameter.

We need a spigot of 44 mm o/d 16 mm long with a projection of 25 mm 4.5 mm long, all bored out to 20 mm for a depth of 36 mm. Renishaw helpfully give an un-dimensioned drawing but I have an SK40 shank to copy - so that's OK

awemawson:
So reaching for my collet set up on the Colchester Master I was surprised to find they don't go as large as 40 mm :bang: OK it looks like a 4 jaw chuck job to get decent concentricity. In point of fact concentricity isn't at all critical as the probe has four screws to adjust it's position - but if you are doing it, it's nice to do it right !

I thought as the three jaw was already mounted I'd pop it in it and see how perpendicular the band saw cut was. Answer: amazingly good :clap: And even MORE amazing just spinning it by hand the shank LOOKED pretty concentric (I'd wrapped it in brass shim to protect it from the jaws). Putting a DTI on and revolving by hand it was SPOT ON :ddb:

So I continued with it in the three jaw and rough turned the two diameters oversize by 2 mm and drilled the 20 mm bore undersize at 18 mm. I'll let it all cool down before the finish machining while I feed the pigs.

awemawson:
So, Pigs fed, part cooled in lathe - time to finish the job.

The two outer diameters were taken down to size, and the bore bored out to 20 mm . Then I mounted it in the milling machine and drilled and tapped the two 8 mm cross threads for the retaining grub screws.

The way it works, is that there are four tiny allen grub screws on the probe body that bear on the smaller outer diameter of the adaptor, and by tweaking them concentricity can (hopefully) be achieved. Then the two 8 mm pointed grub screws in the body of the adaptor bear on a conical washer loosely retained on the rear on the probe body. These screws and conical washers tightly hold the probe body in contact with the adaptor yet allow adjustment.

So that's one more 'round tuit' put to bed :ddb:

Brent Crude:
:beer: Good work, fella!!

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