Insize Coacial Indicator used in Vertex Boring head

Just for fun: I mounted the Insize Coacial Indicator not in a 10mm collet directly in spindle as usual, but mounted the Boring Head 1st, then the Coacial indicator in the boring head itself intended to be as one MT4 swop in spidle rather than two operations.

1-Mount MT4 Boring head in spindle.
2-Make 2mm sleeve and mount 10mm Coacial INdicator in 12mm bore Vertex Boring Head.
3-I never switch on or run the mill motor, just use my hands to turn.
4-I now adjust the boring head outwards for this case to make the indicator read and tention in the larger hole clamped in vice(Just for inllustration.
5-I now chose X & Y axis and turmn table till both are zeroed, it was quick and easy to my surprise, locked table recheck.
6-The spindle is not positioned over the centre of the hole.

7-Now normally the Coaxcial Indicator mounted in the spoindle move only Up & Down as it convert the out of centerness to usefull display on indicator.

8-Now in this case the Coaxcial Indicater is off centre itself, and apart from the legit Up & Down movements as expected, it also moves hoizontall as one would not have expected, but this movement does not effect its function.

I found this interesting regarding the operation of the Coaxial Indicator design and as it is uneffected by other movements other than those surfaces the design relies on.

See both pictures:

I have one at the museum and used it the other day for a similar boring job. I always try to get the axis of the bore lined up with the spindle by eye before selecting a suitable probe. The nylon ring is probably for storage, I'm in two minds whether to leave if off altogether. If your spindle speed can be reduced to under 150rpm, then under power is the best way to get the X and Y axes to the null point. A lot depends on the finish in the bore as a rough one will make the needle jump about badly and make accuracy difficult. You should not use the boring head to hold the coaxial indicator, it should be in a collet running true to the spindle.

In agreement with OM can't see the point of using headroom especially if you do not have much!

I was trying to illustrate that the offset movement of the Coaxcial Indicator when fitted to the boring head as oppose to a collet does not effect its working due to how it works and dependant surfaces, which I found interesting, and in my opinion its still moving around an arc from the spindle centre, similarly as if you not having a coaxcial indicator and using a boring bar/ insert tip to centre the thing either in a bore or around another circular feature visible after the bore was woreout and out of round and you want to bore it out but keep the original geometry of the mesching of the gears making a sleeve. So in this case a Coaxcial indicater would not be usefull, a case like I might be facing if my plan-A in restoring a bansaw & gearbox does not work, so basicly I am just thinking about all of this in all directions and thanks for all other opinions. So its just a theoretical thing, not to say you must do it this way.

Edited By Chris Mate on 30/08/2023 06:02:29