Source for DTI indicator tips with 6BA thread?

[Dave Sawdon 1Participant @davesawdon1]

I need an elephant’s foot for a Mercer indicator but it seems to have a 6BA thread. Any suggestions for stockists?

[Nick HughesParticipant @nickhughes97026]

Hi,

I think you’ll find that it’s a #4 UNF 0.112″ OD 48 TPI thread.

Discussed quite a bit here:-

https://www.britbike.com/forums/ubbthreads.php/ubb/printthread/Board/4/main/63771/type/thread

Scroll to the end for their final conclusion.

 

[Nick HughesParticipant @nickhughes97026]

Left it too late to edit and add this supplier:-

https://www.machine-dro.co.uk/products/mitutoyo-imperial-steel-contact-point-thread-4-48-unf-length-0-375-radius-0-25-101188?_pos=1&_sid=5eba0ecf7&_ss=r

 

[Dave Sawdon 1Participant @davesawdon1]

You may be right, the thread pitch and diameter are so close that it’s difficult to be certain, but the thread angles are sufficiently far apart that there should be jamming on a longer thread. A 6BA nut fits perfectly on an existing indicator point, and a 6BA machine screw goes to the bottom of the hole in the indicator (about 12mm) without any sign of jamming …. so I suspect that it really is a 6BA thread. The thread length on a “point” is quite short so a 4-48 would probably fit, but I’d prefer to get the right one to avoid any risk of jamming or wobble.

[peak4Participant @peak4]

Pretty sure 6BA was a standard thread; the three Mercer gauges I just checked all appear to be 6BA, Baty were different, but it’s too cold out there to dig out a microscope.

Threads on DTI’s

Bill

 

[Speedy Builder5Participant @speedybuilder5]

What is an “elephant’s foot”.  I have a dial gauge “point” which is 1″ diameter with a 0.106″ dia stud.  Never used it, will never need it.  It came from a dial gauge on a stand that was used for measuring paper and carbon paper thickness.  Free to a good home if you donate to a “worthwhile UK charity price of postage.

Bob

[Peter Cook 6Participant @petercook6]

Must fess-up, when I needed one, I simply made one from a bit of scrap with a short length of suitably threaded rod Loctited in. Took about 5 minutes on the lathe and works fine. Probably not accurate enough for a toolroom, but more than adequate for my needs.

[Dave Sawdon 1Participant @davesawdon1]

peak4: my Mercer 1/10th and Baty 5/10 DTIs have the same thread – fairly certain it’s 6BA now.

SB5: a DTI elephant’s foot is just an accurately ground flat disk with an appropriate thread. I need one 8-10mm diameter and 6BA, so thanks for the kind offer but the size and thread are both wrong.

PK6: yes, you’ve made me feel guilty. I hadn’t fancied having to cut a 6BA thread on an 8mm piece of bar and hadn’t  thought of using studding into a tapped disc. I think that, for repeatability, I’d want the disc to have a shoulder that could seat on the face of the DTI “shaft”. I guess I’d turn a tapped cylinder to simulate the DTI in the lathe chuck, screw the foot onto it so the shoulder seats, and then turn the base of the foot – I’d prefer to grind the foot, but I can’t think how to do that … Maybe it’s simpler to “adjust” a 4-48 thread!

[Charles LamontParticipant @charleslamont71117]

I am still using the one I made, oh what, maybe 50 years ago?

[Nick HughesParticipant @nickhughes97026]

How about trying the #4-48 and if it’s not quite right, chase the thread with a 6BA die?

[Dave Sawdon 1Participant @davesawdon1]

Yes, I tried ordering some 4-48 points from Amazon – they sent points with M2.5 threads so I’ve returned them. Damned annoying!

 

[Charles LamontParticipant @charleslamont71117]

6BA fits my Mercer and Baty indicators.

[Howard LewisParticipant @howardlewis46836]

Baty and Mercer, being UK makers of measuring equipment, would expect them to use BA threads on older instruments.

Howard

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