Thread: Elephants foot !

Hi Guys,

I made an Elephants foot for my Mercer dial gauge yesterday !
Does any one know what the correct thread is for the stem ?

I took the original one out and it screws nicely into my M3 thread gauge, but the one I made won't screw into the gauge stem.
I was going to phone Mercer, but its Saturday and they are closed. I've not found anything on line either.

Hi John.

Try UNF 4-48. My similarly threaded Starrett contact points fit my imperial Mercer and Baty indicators.

Bob.

Edit : Clarification added. Thank you Michael.

4-48 is the thread for imperial dial gauges but metric dial gauges according to the long island indicator guys are M2.5.

Michael

Hi Guys,

Thank you for that information !

Particularly the difference between imperial and metric gauges.

Oddly enough the postman has just delivered a padded bag containing a 2.5 mm die.
I now need to figure out how to set up the lathe to single point 4-48.

That's tiny. I had to go look up the thread dimensions of a 4-48 to see the sizing. I'd like to see some pics of your setup when you do it.

Simon

Hi Guys,

You want pictures...
Well all right then !

16-09-2018-001.JPG 16-09-2018-002.JPG
This is the Elephants foot that I made, that doesn't fit. The thread is M3. Its also a 60 degree thread angle.
I've been told that the 4-48 is a 55 degree thread angle. I need to confirm that because I don't have any 55 degree threading inserts.


16-09-2018-007.JPG 16-09-2018-011.JPG 16-09-2018-012.JPG
Simon: This is a piece of 10 mm diameter drill rod/silver steel, 02 grade. I've run out of the 8 mm that I used for the other one.
These pictures were taken whilst turning the bit that is to be threaded, down to 2.90 mm. I need to check that size.

I'll post more pictures when I've made it and it fits of course.

Hi John,

The thread angle for UNF should be 60 degrees - https://britishfasteners.com/threads/unf.html

While you are set up for some diminutive thread cutting maybe consider making an adapter that allows interchangeability of metric and imperial contact points. I made one.

Bob.

Hi Bob, Chris, Guys,

Bob: Thanks for that link. I hadn't looked for the info at the time I made (post 6). I had suspected that I was given bad info about thread
angles. That table nicely gives all the information needed ! I've made a copy of it.

Chris: Yes I will post some pictures when I finish making it. I promise

Is there an easier way to do this ? ie instead of a screw use a hollow tube to fit the elephants foot over the existing tip then secure it somehow. Dont know how feasible that'd be, just a suggestion.

Hi Guys,

Actually I've taken the cowards way out just in case... I've just ordered a 4-48 UNF die.

Originally Posted by BaronJ

Hi Guys,

Actually I've taken the cowards way out just in case... I've just ordered a 4-48 UNF die.

No you didn't.......but I did.
https://www.ebay.com.au/itm/22Pcs-St...QAAOSwfbpblex8

cheers, shed

Hi Guys,

That nice Mr postman has just popped a padded bag through my letterbox ! I now have a nice new presto 4.48 UNF 3/4" inch round split die.
My backup plan

Shed: You will have to let us know what you think of those fittings. They are very tempting

Originally Posted by BaronJ

Shed: You will have to let us know what you think of those fittings. They are very tempting

Actually I bought them from aliexpress, https://www.aliexpress.com/wholesale...ator+point+set not long before the gov put the GST on our imported toys, actually I emptied the piggy bank and stocked up on lots of goodies

They look ok screw in ok and seem to work fine, for under 10 bucks delivered how could I complain.

Strange that the metric size is not available otherwise I would have a set of those also.

cheers, shed

Hi Guys,

As promised !

18-09-2018-3.JPG 18-09-2018-2.JPG 18-09-2018-4.JPG
The setup. Using the new toolpost.
The second picture is setting the threading insert.
Third picture is taking a scratch cut to set cutting depth,

18-09-2018-7.JPG 18-09-2018-6.JPG 18-09-2018-5.JPG 18-09-2018-9.JPG
The result ! It doesn't screw in all the way because the thread doesn't quite make it all the way to the head. I really ought to have under cut the thread a few thou.


18-09-2018-8.JPG
I made a new back whilst I was at it. You all saw the "Wax Chuck" thread, well I stuck the brass disc back on the chuck and faced it. You can see the mark at the centre. Where I guesstimated the tool hight. But I was careful not to let it get hot this time.

Hey BaronJ,

Good job, well done.
What sort of rpm did you have to run to use a carbide tool to cut a thread on a tiny diameter ?

I've recently been amazed at how sharp some carbide bits can be and that they can cut nice finishes running at the relatively slow speeds that my little old 9" Hercus is capable of - top speed 720rpm. A carbide thread cutting bit is on the list called "try this on day" .......

Bill