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Making-A-Taper-Gauge

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awemawson:
I've decided that to make progress on the A2-6 to A2-5 adaptor for the Beaver TC20 lathe I need to make a male taper plug gauge to fit the recess in the existing chuck, so that I can test the taper that I create in the adaptor 'as I go'

The plan of attack is to make a taper gauge slightly 'longer in the taper' (really fatter as it's a disk) than the finished article. Then once the existing chuck is removed carefully measure how much fatter it is, and reduce the disk thickness on the surface grinder to 'dead nuts on'.

So I needed a 15 mm or so blank about 110 mm in diameter. Irritatingly I already had a 12 mm thick one that had been destined to be a gear wheel, but 3 mm too thin. The next (and only!) thick plate that I had left was a section of very rough and rusty 20 mm 'road plate', the sort of thing they put over holes to allow traffic still to run.

So major clean up with wire brushes and grinders, followed by marking out, and slicing close to size on the band saw.

That's as far as I can go today as we have three of the grand children and their parent's for the first 'post lockdown' outside meal round the fire pit.

But next step is to turn it circular on the manual lathe, approximate the taper again on the lathe, then mount it between centres on the J&S 1300 EUIR cylindrical grinder and try and remember how to set precise angles on it's swivelling table. (I've not used this beast for literally several years, but I steamed it up last night and it was smooth as silk !)

More to follow - obviously !

nrml:
Is the final finish on the back plate going to be ground or left as a turned finish?

awemawson:
Not sure yet - if the turned finish is 'OK' then I'll press on with other things, but if I need to cover my tracks I'll grind it !

(I'm hoping to be able to grind both the male and female tapers though. (I have enough internal grinding spindles for the J&S 1300 to sink a battleship !

awemawson:
Main task today was to clean up that 'almost circle' by first tickling both sides on the surface grinder before turning it actually circular on the manual lathe. but . . Slow start this morning for several reasons:

- Late arising due to exhaustion from three grandchildren yesterday

- Had to fit the replacement extraction vacuum motor for the big disk sander - replacement arrived yesterday (Bank Holiday so don't knock Hermes !)

- Searched high and low for my box of slip stones to no avail - they've disappeared !

Although the surface grinder magnetic chuck is nicely ground flat and true, I like to gently pass a fine slip stone over it before use to ensure no burrs have been raised since last use - humph, need to order some more !

So pressing on I decided to let the spindle warm up to equilibrium (as you always should with precision grinding) while I checked hydraulic feeds and coolant flow.

. . .  no coolant flow ! - it uses a 'weir style' coolant settling system which is excellent for letting the very fine particles settle out of suspension, but it does (by design) have a very large surface area. This needless to say results in evaporation over time of the water content of the soluble oil coolant. In the end I had to add 6 gallons before the pump head once more was under the surface and delivering coolant.

. . . so no actual grinding yet, hopefully this afternoon but now other duties call.

awemawson:
I eventually got back into the workshop and managed the first rough grinding of one side of the source plate to give me a flat surface when I mount it on the milling machine to bore the central hole for mounting between centres and subsequent turning operations.

Finish isn't fantastic with a bit of herringboning but I was taking it off at 2 thou a pass - final pass 1 thou, total removed 10 thou

Video still  uploading but it will be here :

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