Curious as to who supplied movements to Golay.

John Matthews

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Sep 22, 2015
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Ethan - from what I have read and the photographs I have seen, I believe the finish of the McCabe is machine spotting, using a spotting engine.

I am happy to be corrected by a marine chronometer expert, but I would not be surprised if the finish of your karrusel was achieved in the same manner. I think the finish would be described as machine spotting. What I don't know is whether these so called 'spotting engines' continues to use a stone stylus at the end of the C19th beginning of the C20th. gmorse or SKennedy may well be able to clarify.

John
 

gmorse

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Hi John,
...may well be able to clarify
In your post #45, in the 1878 HJ article, it refers to the tip of the spotting arbor being made of bone and applied with either powdered charcoal in oil, or better still, diamantine. This would seem to me to have a gentler action than Water of Ayr stone, although this is very soft, and bone would probably keep its shape better than the stone. I suppose a boxwood tip would produce a similar result, or perhaps an up-market version could use ivory, (elephant or walrus); no CITES back then!

I think Ethan's McCabe was done on a straight line engine.

Regards,

Graham
 

John Matthews

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Ethan's Neill karrusel on the left, McCabe on the right (not vertical, so lines of circles do not appear orthogonal) ...

1663951984246.png


John
 

Ethan Lipsig

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Graham, you replied " I think Ethan's McCabe was done on a straight line engine." Sadly, the McCabe isn't mine. I presume you would also think that a straight-line engine was used to make the similar decoration on my Neil PL Bonniksen karrusel and Dr. Jon's Breyer in the immediately preceding postings.
 

gmorse

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Hi Ethan,

It's possible, but much clearer close-ups of the Neil are needed to confirm or otherwise. Looking at the McCabe now, and Jon's Breyer, they may have been done on a spotting engine, since the pattern looks more like rows of circles.

Regards,

Graham
 

gmorse

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Hi Ethan,

Thanks for these, I think they prove me wrong, in that the patterns do appear to have been made by very accurate registration on a spotting engine. The precise degree of overlap of the circles leads to the illusion that they're square; it's a very nice piece of work.

Regards,

Graham
 

John Matthews

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So the conclusion is that all these examples are either hand or machine spotting. While this confirms my suspicion I am still do not know whether Water of Ayr stone was used in spotting engines throughout the time of their use.

John
 

gmorse

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Hi John,

I would have thought that Water of Ayr or Tam O' Shanter stone would be rather soft and subject to wear, which would tend to reduce the accuracy of the impressions made as it wore down. It would be rather hard to test this now, because as far as I know it hasn't been quarried for many years and supplies of old stocks only turn up very occasionally; anyone who still has some would probably rather keep it for their own use!

Regards,

Graham
 

SKennedy

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Jan 5, 2017
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I've not really much to add to what's been said. You could do that pattern on an ornamental lathe - or indeed a rose engine that has a drilling attachment - using the cross slide ratchet for horizontal movements between circles with the work held on an eccentric chuck that is adjusted for vertical movements of known distance between rows. The work itself would not rotate.
I think to get that pattern the tool would have to be slightly concave or perhaps even tubular so as to create a circular outline. I've not tried it (yet!) but if/when I do, as a starting point, I think I'd use a soft steel tube and charge the end with oilstone paste. If the tube wears during the process it would make no difference to the pattern.
 

GordonM

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Feb 15, 2020
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There is a drawing and description of a spotting tool in Britten's Handbook.
I have what I believe is part of one which looks to be intended to fit on a Lancashire mandrel. Not sure how the indexing would be done. The spring loaded spindle has a tiny hollow cylinder of horn at the tip, to be used with an abrasive - possibly coarse red stuff (iron oxide) or Water of Ayr stone dust.
The finish is very shallow, even a light polishing would almost remove it. I have seen a Barraud pocket chronometer where the spotting is hardly visible.

Angus
 
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