Myford Super 7b lead screw end float

[egaParticipant @ega]

Posted by Michael Gilligan on 17/12/2019 22:51:54:

The quest for a clear reference for Hemingway’s assertion continues …

I can, however, quote this verbatim from page 26 of the fifth edition of ‘Testing Machine Tools’

[quote]
.

(2) Axial slip.

We have to distinguish between axial (or end) play and axial slip of a spindle. End play means the indispensable freedom of a spindle moving in the axial direction to prevent it from seizing by heating. This end play, specially on high – speed machines, should be within the specified limits and uniform running.

Axial slip (axial sliding motion) is defined as the axial spindle movements which may repeat positively with each revolution as a consequence of manufacturing errors. It is only this axial sliding movement that is to be tested, and the specified tolerances apply only to this movement. To measure axial slip correctly, the spindle must be forced in one direction by an applied axial thrust to ensure that the end play remains the same throughout the test.

[/quote]

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Please note Dr. Schlesinger’s careful distinction

MichaelG.

Thank you. This seems to explain the Hemingway reference to "oscillation". The phenomenon is perhaps similar to the motion induced by a swash plate.

Edited By ega on 17/12/2019 23:10:46

[HopperParticipant @hopper]

Methinks applying Schlesinger limits for the manufacture of new high-precision industrial machines to a 50-year-old low-cost home hobby machines is overthinking things a bit.

Edited By Hopper on 18/12/2019 05:24:11

[Michael GilliganParticipant @michaelgilligan61133]

For a ‘benchmark’

The permitted maximum periodic axial slip for the main spindle of this Harrison lathe was 0.0004”

See test G4 **LINK**

https://www.harrisonlathes.com/pdfs/harrisonaccuracychart.pdf

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 18/12/2019 00:03:53:

Methinks applying Schlesinger limits for the manufacture of new high-precision industrial machines to a 50-year-old low-cost home hobby machines is ludicrous.

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…. and particularly ludicrous is; implying that a kit for improving the leadscrew slip on a Myford can be constructed to the accuracy of a Harrison spindle.

I would like to see the detailed instructions !!

MichaelG.

[Tony Pratt 1Participant @tonypratt1]

Posted by Michael Gilligan on 18/12/2019 00:10:13:

For a ‘benchmark’

The permitted maximum periodic axial slip for the main spindle of this Harrison lathe was 0.0004”

See test G4 **LINK**

https://www.harrisonlathes.com/pdfs/harrisonaccuracychart.pdf

MichaelG.

Reading that test report I get the feeling that somebody actually tested the lathe rather than printed off 1000's of identical reports to be sent out to unsuspecting customers.

Tony

[DiogenesIIParticipant @diogenesii]

..maybe the most careful assembly and close tolerances are to be found in the structure of Hemingway's opening paragraph

[John HaineParticipant @johnhaine32865]

Posted by Brian Oldford on 17/12/2019 21:16:49:

Posted by John Haine on 17/12/2019 13:13:08:

But just to note that Hemingway charge £27 for £10 worth of thrust bearings and some bits of steel and bronze. There's no need to replace the existing bush so you don't need the bronze; and the end caps to position and shield the thrust bearings can be made from a scrap of 1 inch steel bar that may well be in your scrap box.

For intellectual completeness could you provide a bearing part No?

I gave a link further up the thread – I can't remember what diameter the LS needs so can't give the part number.

[NilochParticipant @niloch]

Thank you to all respondents but especially to ega and Nick Hughes for their germane contributions of 16/12 and 17/12 respectively.

[Author]

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