Precision division plates

Not cross purposes really. The precision indexing between the two halves is a given and that all make sense, what I am unclear about is how they locate the (bobbing up and down) lower half of the coupling to the same or better level of accuracy.

Maybe the bottom half of the coupling is solidly mounted to the base and it is the table (with what ever is on it) that is lifted to allow rotation.

Ian P

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That ^^^ was always my assumption

... but I may be wrong.

MichaelG.

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Assumption vindicated:

http://www.lightglassoptics.com/7-Ultradex-Rotary-Table-Model-B_p_862.html

Edited By Michael Gilligan on 10/03/2019 00:34:03

Hi All

An online calculator to generate a a Hirth coupling. I remember seeing this link a while back a bit of searching and I found it, It is still there! quite well executed too.

Hirth coupling Calculator.

Regards
John

Edited By John McNamara on 10/03/2019 03:50:11

Newbould indexers use a Hirth coupling and they are supremely repeatable.

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That's a thing of beauty, John ...Thanks for the link.

MichaelG.

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A little searching found this on RJ Newbould's site: **LINK**

http://www.newbould.com/stainlessindexer.htm

Nice device !!

MichaelG.

Update:

RJ Newbould made some very interesting contributions to the Pactical Machinist forum: **LINK**

https://www.practicalmachinist.com/vb/general-archive/ot-mother-invention-159279/

Sadly, culminating with this thread:**LINK**

https://www.practicalmachinist.com/vb/shop-management-and-owner-issues/fyi-my-exit-328594/

MichaelG.

Indeed; it happens to us all eventually, but still a great shame. His posts were always a pleasure to read, informative, helpful and polite.

Andrew

I just found in MEW #52 an article about making a "face geared indexing table". It uses a Hirth coupling. It was cut not using any bevel so only the outer edge makes contact.

In #54 Scribe a line there is further discussion about setting the correct angle to cut teeth that mesh properly.

.

Just for info.

Trying to follow-up on the RJ Newbould references

[see also: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=109149&p=2

I drew a blank on the Smithsonian pages. ...

So, I wrote to them asking about the 'Basic Mechanisms' collection. and received to following reply from Jennifer Gloede, Outreach & Collections Specialist, National Numismatic Collection

[quote]

Thank you for your email. Many objects in the engineering collection can be found here:

http://americanhistory.si.edu/collections/subjects/engineering-building-and-architecture

The Newbould devices are not yet online but should be available later this year when more of the museum's collection is published online.

[/quote]

MichaelG.

Edited By Michael Gilligan on 18/03/2019 15:30:30

Err, in which case it wasn't a Hirth coupling but simply a radial spline. By definition a Hirth coupling uses tapered teeth that mate over the full length. The scribe a Line in #54 describes the mathematics to make a Hirth coupling.

Andrew

Re-reading 'Scribe a Line' in MEW #54, I noticed mention of Voith

... Their portfolio is impressive: **LINK**

http://voith.com/corp-en/hirth-couplings/hirth-rings.html

MichaelG.