I did indeed consider modifying an existing tool, and even put aside for it something from my come-in-handy stock, that appears to be some special tool modified from perhaps a boring-head shank or slitting-saw arbor.
In the event I found a way to complete the immediate task, ending 34 aluminium rods to length; but I still want the depth-stop, and all the above advice has led to me considering my intended design more carefully.
It led too, to examining my two Baty dial test indicators more carefully, to find they both have two probe tips, one hemispherical, the other only slightly convex. I found ARC Euro sell tip sets to fit indicators with standard 4-40 UNF threads: I had not known of that standard. Happily, very careful measuring revealed the two Baty ones are so made.
In extremis a 6BA male thread would probably fit the socket – the diameter and pitches are very close, and the main difference is in the thread angle.
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After I finished facing the 34-off rods to length and drilling their ends for tapping, I looked at the lathe to gain some idea how to mount the DTI on centre-height. The best way seems an angle-plate that would temporarily replace the QCTP, to put the indicator's fixing lug below the top-slide surface.
So this is one enquiry that went further that I had thought it would!
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A note on that batch work.
I knew from the outset that drilling the rod ends to depth on the lathe would be very slow, laborious and tedious; and physically awkward and uncomfortable with a conventional tailstock.
So I broke the work into sections thus:
Lathe:
1) Face one end of each sawn blank.
2) Set a depth-stop on the lathe, and face all the second ends.
3) Spot-drill all ends, but drill one to about half-depth (so about 1/2" ).
Bench-drill:
4) Put a 3-jaw chuck on a Myford-accessory nose-piece fitted to a base-plate – I made this a couple of years ago, complete with table-register, to use on the jig-borer. Mount this assembly on the bench-drill, using the drilled rod for alignment, and standard T-slot clamps on the base-plate .
5) Drill all 68 ends to depth, taking advantage of the Meddings machine's speed, sensitive quill and comfortable operating access.
6) Lightly countersink all.
They are now ready for tapping, using a tapping-head on the Progress 2G bench-drill on its low speed. I have already set a Record drill-vice for this but the 3-jaw chuck will be better.
An aluminium-foil pie dish with a central hole makes a reasonable shield to stop most of the chips from falling down the chuck.
Edited By Nigel Graham 2 on 29/05/2023 23:50:12