Co-axial centre finder, how do i use it.

[geoff5269]

I recently bought one of these when I saw a special offer price and looked forward to trying it. but I couldn't see how it would work when trying to centre in a hole, I could make it work for a outside diameter. I realised that the lever where you insert the feelers is loose but could not tighten it. surely this should have some resistance like the lever on a DTI. can anyone help.
For anyone thinking of getting one check you have enough clearance between the work and the chuck, 6" is the very minimum and then you can only use the short feelers.
Thanks Geoff

[Jasonb]

You use it in the same way as you would on the OD, once the feeler is in the hole you can move it against friction so that the feeler then runs against the inside of the hole.

The dome head nut should hold the joint firm but not solid so you can easily adjust position.

[crueby]

Agree with Jason's comments - the tip can run on the inside edge of a hole. The nut on the arm just needs to hold it firm enough so it does not slip by itself, but let you shift it one side or the other so you can span wider cylinders. Very handy tool if it will fit on your mill. I have the taller column on my Sherline, so it just fits. Its also useful on the lathe, hold it from the tailstock to indicate on parts in the chuck.

[jadge]

My co-axial centre finder has a small knob on the back that in one position spring loads the pointer inwards for OD and in the other position spring loads the pointer outwards for ID. All I need to do is move the knob to change from ID to OD. There are no nuts to adjust?

Andrew

[Art K]

I've got one that I bought at the names show from little machine shop. Then proceeded to not use it till I needed to indicate a hole at work. I use it fairly often now that I've gotten over the idea of turning the spindle on with an indicator in it. Mine has no means of changing from ID to OD but does have 6 tips, 3 bent and 3 straight. You do need a lot of room even with the short one.
Art

[Dave Otto]

Typically you you use the curved tips for OD work and the straight tips for ID.

Dave

[crueby]

I've got one that I bought at the names show from little machine shop. Then proceeded to not use it till I needed to indicate a hole at work. I use it fairly often now that I've gotten over the idea of turning the spindle on with an indicator in it. Mine has no means of changing from ID to OD but does have 6 tips, 3 bent and 3 straight. You do need a lot of room even with the short one.
Art

Nice thing about a small mill, can spin it by hand easily!

[Art K]

Yes I turn the spindle by hand to get it a semblance of centered. Then turn on the spindle and just move the dials on X&Y till the needle stops moving and its centered.
Art

[jadge]

Yes I turn the spindle by hand to get it a semblance of centered. Then turn on the spindle and just move the dials on X&Y till the needle stops moving and its centered.

Same here, with the spindle at about 120rpm.

Andrew

[PJPickard]

On the B'port style mills that I use them on I just put the machine into neutral and spin by hand.

[geoff5269]

Thanks for all your replies, very helpful
 I now see that the tightening screw has a stripped thread and that's why it wouldn't grip. Its a very well made item spoilt by this small defect. I shall try replacing it with something stronger.
Geoff

[retailer]

The first time I used mine I didn't realise that the top plastic spacer was a 'transport' spacer and needed to be removed, had a lot of trouble before it finally dawned on me to remove it. I turn by hand and do the X axis first then Y axis.

[Art K]

I use mine at work on the 660 rpm pulley, that way I don't have to change the speed and it is well within the 800 rpm max.
Art

[bob in nebraska]

I too bought a coaxial indicatot from Little Machine Shop.  At first I thought it was defective, but soon realized that it is very sensitive to any error in the collet or chuck. My R8 collet in the mill, or MT3 collet in the lathe headstock, give good results. The center as found with the coaxial agrees ith the center found with a wiggler or conventional indicator such as a "last word" or DTI in an Indicol. But when I hold the coaxial in a drill chuck or imported ER collet adapter there is serious centering error. The indicator must be CO-AXIAL with the axis of the machine!

Well let me qualify that. If you mount the indicator in a high quality four jaw chuck, and offsett it deliberately, it will still indicate a true center. So long as the indicator axis is "exactly" parallel to the machine axis, and not so far displaced that the coaxial indicator has insufficient range of motion, it will be a true center.

I had many happy hours trying out different combinations of instruments and chucking methods, kept careful notes,  and when done had a much better idea of the relative accuracy of my collets and chucks. I now trust my coaxial becsuse I understand its limitations.

Note that the simple wiggler is a very good way to center. It is completely insensitive to chuck error.

Finally, note also that the markings on the coaxial are relative, due to the varying length of the sensing arm.They are not .001 inch or .01 mm except perhaps for one of the sensing arms.

[ShopShoe]

I've been following this thread.

One thing I found with my similar indicator is that the mounting shank was 10mm. I had to get a 10mm R-8 collet to make it more easy to set up in my mill. My closest inch collets were not suitable.

Did anyone else have this issue?

--ShopShoe