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M&W Straight-Edge Set

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Clive Brown 122/04/2019 16:52:40
234 forum posts
7 photos

I have an ancient boxed set of Moore & Wright Toolmakers Straight-edges. M&W part no. 315. Four steel straight-edges from about 2" to 5" in length and also a length of what looks like a piece of black glass about 5" x 1" x 0.25".

Does anyone know the purpose of this "glass"?

Clive

JohnF22/04/2019 16:55:46
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824 forum posts
92 photos

Probably an "optical flat" used as a reference for the straight edges

John

Might have an old M & W catalogue somewhere will try and find it to see if the product is in it

Lambton22/04/2019 17:14:34
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674 forum posts
2 photos

Clive,

I have a 1965 M&W catalogue that refers to : part No 315TP as Black Glass test piece only 30/- each. (£1.50 )

I hope this is of help.

Eric

Michael Gilligan22/04/2019 17:15:52
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13306 forum posts
578 photos
Posted by JohnF on 22/04/2019 16:55:46:

Probably an "optical flat" used as a reference for the straight edges

John

.

That's an interesting thought, John [and I can offer nothing better at present] ... but it seems rather unlikely: All the 'Optical Flats' that I have used have been transparent, so that you can see the fringes.

MichaelG.

Michael Gilligan22/04/2019 17:22:23
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13306 forum posts
578 photos
Posted by Lambton on 22/04/2019 17:14:34:

Clive,

I have a 1965 M&W catalogue that refers to : part No 315TP as Black Glass test piece only 30/- each. (£1.50 )

I hope this is of help.

Eric

.

Mmm ... I wonder what nature of test was intended

MichaelG.

Plasma22/04/2019 19:33:08
298 forum posts
40 photos

I suggest the same as when using the straight edge to check a machined surface, but the glass is as near perfect as possible I.e. stable at variable temperatures etc. Black glass so its opaque when holding it up to the light. ?

Rod Renshaw22/04/2019 19:43:10
42 forum posts

I have a set, and a M and W catalogue which lists and describes these.

The test piece is a piece of plate glass and the test is to lightly press a straight edge against the glass and hold both up the light to see if any light comes through.

I read somewhere that a gap of one tenth thou inch will shown as a coloured light (I can't remember what colour!) and a larger gap will show as white light, assuming the background light is white.

My set seem to be very good when I try this test, probably because they were well made originally and I don't use them much. I suppose a professional toolmaker using them repeatedly would need to test to be sure his set were not wearing.

Rod

Nicholas Farr22/04/2019 19:59:47
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1883 forum posts
919 photos

Hi, this says it all.

straight edges001.jpg

Regards Nick.

P.S. I have the 6" one, which cost 11/9 = 58.75p in todays money.

Edited By Nicholas Farr on 22/04/2019 20:14:25

Clive Brown 122/04/2019 20:08:56
234 forum posts
7 photos

Thanks for all the comments. Another minor mystery solved. My piece of glass isn't marked "test-piece" as the catalogue illustration seems to suggest.

Clive

Clive Foster22/04/2019 21:13:52
1750 forum posts
56 photos

Clive

Its the case that is marked test piece not the glass itself. Pretty sure my personal set just has the naked glass but at least one of the guys at work had the glass in a separate case which, I think, was so marked.

Hafta say that I use mine so little that I haven't actually seen them for around 3 or 4 years! Box got moved around during a tidy up.

Clive

Michael Gilligan22/04/2019 21:58:36
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13306 forum posts
578 photos
Posted by Plasma on 22/04/2019 19:33:08:

I suggest the same as when using the straight edge to check a machined surface, but the glass is as near perfect as possible I.e. stable at variable temperatures etc. Black glass so its opaque when holding it up to the light. ?

.

That makes sense yes

... and Nick's image confirms it.

MichaelG.

Edited By Michael Gilligan on 22/04/2019 22:01:23

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