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Device for cutting very fine screw threads

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Michael Gilligan18/01/2023 18:27:41
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A sublimely ambiguous title for a patent !

… But coming from Hilger & Watts we can be reasonably sure that the threads would be both ‘very fine’ and ‘very fine’

Enjoy: **LINK**

https://worldwide.espacenet.com/patent/search?q=pn%3DUS2717401A

MichaelG.

old mart20/01/2023 20:42:01
4655 forum posts
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Difficult to understand, but it looks to me that differential threads are involved to get the super fine pitches.

Michael Gilligan20/01/2023 20:54:51
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Posted by old mart on 20/01/2023 20:42:01:

Difficult to understand […]

.

Yes, I’m sure it all made perfect sense to them … whilst they were dictating to some innocent typist surprise

MichaelG.

old mart20/01/2023 21:11:29
4655 forum posts
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To get 100tpi,you only need 20 and 25 tpi threads working against each other.

Michael Gilligan20/01/2023 21:26:58
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23121 forum posts
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Yes but … did you notice the number in the opening lines

MichaelG.

old mart20/01/2023 21:35:17
4655 forum posts
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No, you have lost me there. Perhaps it would have been better to read "a device for cutting very fine pitch screw threads".

Edited By old mart on 20/01/2023 21:37:18

Michael Gilligan20/01/2023 21:39:12
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[ deleted … wrong image ]

Edited By Michael Gilligan on 20/01/2023 21:46:03

Michael Gilligan20/01/2023 21:45:09
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23121 forum posts
1360 photos
Posted by old mart on 20/01/2023 21:35:17:

No, you have lost me there.

.

4e208fba-7ea0-4f6e-9531-3602be3bef82.jpeg

duncan webster20/01/2023 23:20:08
5307 forum posts
83 photos

15000 turns per inch isn't a thread it's a surface finish. My starting point for plain turning is 0.004" per rev feed, historical because that's the slowest I could set up on my first lathe. This is 250 turns per rev.

Edited By duncan webster on 20/01/2023 23:20:32

Martin Connelly21/01/2023 00:35:39
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2549 forum posts
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I have not read the patent beyond what is in the image above but I think the idea is to produce a movement 1/15000" per revolution of a knob or shaft which is equivalent to a very fine pitch screw but is not a physical very fine pitch screw. Easily achieved with differential pitches.

Martin C

Ady121/01/2023 01:34:14
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6137 forum posts
893 photos

So its a gearbox?

for slow speed

Roger Hart21/01/2023 08:32:43
157 forum posts
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This reminded me of a Sci Am article - Vol 232 no 4 April 1975 in their Amateur Scientist section. Described a grating ruling engine built by Brian Manning for ruling interferometer gratings.

The screw pitch problem was addressed by a fine pitch screw of sane tpi driven by a small motor/gearbox with a feedback system controlled by a small interferometer looking at the exact number of wavelengths moved at each step. Used a photomultiplier and a homebrew discharge lamp.

All mounted in a big cast iron box to control temperature etc. This chap even evaporation coated in aluminium his own glass plates and made the diamond cutting tool to make the grooves.

Michael Gilligan21/01/2023 08:50:01
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Posted by Martin Connelly on 21/01/2023 00:35:39:

I have not read the patent beyond what is in the image above but I think the idea is to produce a movement 1/15000" per revolution of a knob or shaft which is equivalent to a very fine pitch screw but is not a physical very fine pitch screw. Easily achieved with differential pitches.

Martin C

.

Then [assuming you are interested] I suggest you do read the patent.

MichaelG.

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