Machinability of Drill-Rod

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Stub Mandrel on 27/09/2012 21:14:01:

> Reuleaux … as mentioned, and linked, in my post.

You don't seriously expect me to re-read the entire thread before replying

Neil

No … but I would recommend you look at the second link in my post, above [just edited]; especially the bit about the Wankel engine.

MichaelG.

[Sub MandrelParticipant @submandrel]

Hi Michael,

I skipped the maths, but interesting to see the theory about how a lobate broach can be used to make a square hole.

I used to have a MKII RX7; if people think silent electric cars are spooky they ought to try being in a wankel-engined car when the over-rev warning goes off. Bicycle clip time!

Neil(Why does "fixed centrode" make me think of Stanley Unwin?)

Edited By Stub Mandrel on 28/09/2012 20:56:22

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Stub Mandrel on 28/09/2012 20:54:09:

Hi Michael,

I used to have a MKII RX7; if people think silent electric cars are spooky they ought to try being in a wankel-engined car when the over-rev warning goes off. Bicycle clip time!

Neil

I always fancied one of those Mazdas ! … Somewhere in my archives I think I still have an article from "Cars & Car Conversions", where they tuned-up the early saloon, simply by fitting a free-flowing exhaust system. If I find it, I will let you have a copy.

MichaelG.

[David LittlewoodParticipant @davidlittlewood51847]

On the subject of constant-width sections, it is worth noting that a 90 degree V-block will not always detect this deviation from roundness. For example, a 7-sided constant width section will show zero deviation in a 90 degree block as measured vertically above the V. (If you doubt this, those in the UK can try it with a 50p piece.) A similar false pass will apparently be recorded by shapes with 9, 15 or 17 undulations, though I haven't tried this.

There is in fact a British Standard setting out in great detail the tests required to establish roundness (BS 3730, 1987, if you are interested). You may need to use several V-blocks of different included angle to establish true roundness, though a block of 72 degrees will work for all symmetries up to and including 18.

There is an infinite family of constant-width shapes, of which the symmetrical examples are only special cases.

David

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