Old rule divisions twelfs etc

[Howard LewisParticipant @howardlewis46836]

Jason,

As a rule, I use a digital Callliper, or a Micrometer!

[david bennett 8Participant @davidbennett8]

Posted by Howard Lewis on 02/10/2021 13:17:29:

Jason,

As a rule, I use a digital Callliper, or a Micrometer!

I assume that was tongue-in -cheek. Very good -but could you use a rule (of the measuring type) to measure that 0.001" ?

dave8

Edited By david bennett 8 on 03/10/2021 06:07:50

[Howard LewisParticipant @howardlewis46836]

Dave B

I couldn't, but my turning instructor once put his knarled thumb and worn rule against my job and told me that I had "About 0.010" to take off. The depth mic told me 0.008", so he probably could have!

My Milling instructor told us always to check a steel rule. It was easy to be accurate with the small subdivisions, but get bit wrong by losing sight of the inches!

Howard

[BazyleParticipant @bazyle]

Anyone remember the film Saturday Night and Sunday Morning (1960). The lead character was a lathe operator on piece work and said that he didn't measure the parts because he could get to size without and it would slow him down.
I wonder when that job (bicycle axles) went CNC. It was a bit odd that it wasn't an Automatic but may have been poetic licence by the scriptwriter to establish his devil-may-care attitude but based on some research of real machinists comments.

[david bennett 8Participant @davidbennett8]

Howard, your instructor had good eyes.Thats about the maximum resolution of a good steel rule (without using a microscope )

dave8

Edited By david bennett 8 on 04/10/2021 00:45:15

[Nigel Graham 2Participant @nigelgraham2]

Bazyle –

I remember that fim scene. The character (played by Albert Finney?) was operating a capstan-lathe and looking beyond the notion of dramatic licence, it's quite possible his real-life version would have had the lathe set up for him, and taken the setter sufficiently on trust not to need measure the piece-parts himself.

The inspector would have measured the first two or three off and maybe odd ones at intervals, and once happy, let the turner carry on until the long-awaited clocking-off time broke the monotony.

Automatic or semi-automatic lathes, controlled by cams profiled for the work, had been around though, and for decades before 1960. One photo I have seen appears to show the cams as strips screwed to a perforated drum on the outer end of the headstock, but I don't know how their motion was transmitted to the saddle, etc.

+++

As for losing sight of the inches as Howard warns, I manage to lose sight of whole inches, not just mere one-hundredths of them!

[SillyOldDufferModerator @sillyoldduffer]

Posted by Bazyle on 03/10/2021 17:57:30:

Anyone remember the film Saturday Night and Sunday Morning (1960). The lead character was a lathe operator on piece work and said that he didn't measure the parts because he could get to size without and it would slow him down.
I wonder when that job (bicycle axles) went CNC. It was a bit odd that it wasn't an Automatic but may have been poetic licence by the scriptwriter to establish his devil-may-care attitude but based on some research of real machinists comments.

I think that very possible. The film script was developed from his own novel by author Alan Sillitoe, who in 1942 started work aged 14 in a Raleigh Bicycle Factory.

Dave

[david bennett 8Participant @davidbennett8]

Howard,your instructor was probaby sub-dividing the line on the rule by eye. If you know the thickness, it's not too hard to make an estimate. My Rabone lines are about 16 thou, a B andS vernier line is about half that, but thats too fine for a practical rule. The point is that this makes the rule imprecise (after all, your instructors excellent estimate was 20% out! )

dave8

 

 

 

 

 

 

Edited By david bennett 8 on 04/10/2021 21:58:24

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