Device for cutting very fine screw threads

[Michael GilliganParticipant @michaelgilligan61133]

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.

[Michael GilliganParticipant @michaelgilligan61133]

[old martParticipant @oldmart]

Difficult to understand, but it looks to me that differential threads are involved to get the super fine pitches.

[Michael GilliganParticipant @michaelgilligan61133]

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

MichaelG.

[old martParticipant @oldmart]

To get 100tpi,you only need 20 and 25 tpi threads working against each other.

[Michael GilliganParticipant @michaelgilligan61133]

Yes but … did you notice the number in the opening lines

MichaelG.

[old martParticipant @oldmart]

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 GilliganParticipant @michaelgilligan61133]

[ deleted … wrong image ]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by old mart on 20/01/2023 21:35:17:

No, you have lost me there.

.

[duncan webster 1Participant @duncanwebster1]

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 ConnellyParticipant @martinconnelly55370]

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

[Ady1Participant @ady1]

So its a gearbox?

for slow speed

[Roger HartParticipant @rogerhart88496]

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 GilliganParticipant @michaelgilligan61133]

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.

[Author]

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