Gauge Blocks

[Neil WyattModerator @neilwyatt]

Various sources suggest that sets should include pads, one for oiling for storage, and one for celaning off teh oil prior to use.

It's interesting that rubbing on a stone followed by a check on an optical flat is the approved way of reconditioning burred blocks!

Neil

[Rik ShawParticipant @rikshaw]

Two slips wrung together WITHOUT oil give this result:

Wrung together with oil give this result:

The difference is there as can be seen – with oil we get +.00025" approx. I repeated this five times and got similar results each time.

Rik

[Michael GilliganParticipant @michaelgilligan61133]

Trouble is, Rik … the Dial Test Indicator is not really a suitable tool for checking the thickness of Slips; so I'm not sure what your results actually demonstrate.

MichaelG.

Edited By Michael Gilligan on 01/11/2014 14:23:27

[Phil H 1Participant @philh1]

Posted by Bodgit Fixit and Run on 01/11/2014 12:29:27:

I was always taught that they should not be oiled but used dry. The holding force is due to the very fine finish which is why wringing works. Oil will give a false reading and if I remember correctly from my apprenticeship a thin film of oil can take the equivalent of 40 tons per square inch to squeeze out. They will hold together with oil because of the viscous effect and tackiness of the oil but won't give a true reading.

Totally agree with this. My teacher at school, lecturers at college (practical ), lecturers at college (theoretical ), apprentice instructors, chaps from the toolroom and guys from the inspection departments at work all said the same i.e., wring them dry. Interesting if they were all wrong.

PhilH

[Mark CParticipant @markc]

Andrew,

Did you know there are (and have been for a while, just not often mentioned) analogue output inductive sensors? They are more robust than LVDT's although they don't have the same resolution (as an aside, the resolution you mention is probably the sensor you used rather than the LVDT as they have infinite resolution only limited by the signal to noise ratio in the system/amplifier etc). They also do not have the same stroke range (measuring distance) as some long stroke LVDT sensors and they require a metallic target. 

Mark

Edited By Mark C on 01/11/2014 15:03:33

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Phil H 1 on 01/11/2014 14:52:35:

… Totally agree with this. My teacher at school, lecturers at college (practical ), lecturers at college (theoretical ), apprentice instructors, chaps from the toolroom and guys from the inspection departments at work all said the same i.e., wring them dry. Interesting if they were all wrong.

.

Not for the first time on this forum: I think we have more than one interpretation of apparently "obvious" descriptive terms [in this instance, those terms are "dry" and "oil film"].

Careful reading of Appendix B in the NIST document [referenced above] should clarify the matter.

… it's only a couple of pages; unless you follow all the references

MichaelG

[michael coleParticipant @michaelcole91146]

Yes, what may appear to be dry to us, would indeed have a very thin oil film.

Mike C

[Rik ShawParticipant @rikshaw]

Michael – If this method of measuring is good enough for the inspection department at Cincinnati Milacron machine tools then its good enough for me!

As for what the results demonstrate, I would have thought that was perfectly obvious.

Rik

[Gordon WParticipant @gordonw]

I was taught that gauge blocks wrung together by air pressure, always believed that. No doubt someone will know better.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Rik Shaw on 01/11/2014 15:31:36:

As for what the results demonstrate, I would have thought that was perfectly obvious.

Rik

.

Rik,

Based on your pictures, I presume that you have measured the thickness of your applied oil film.

With the greatest respect: I can see no evidence that you have measured the thickness of the slips.

Please … before replying, read Appendix B of the NIST document, and note my point about the differing interpetations of apparently simple terms.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Gordon W on 01/11/2014 15:33:47:

I was taught that gauge blocks wrung together by air pressure, always believed that. No doubt someone will know better.

.

Gordon,

At the risk of labouring this discussion …

NIST knows better, and has kindly given us Appendix B of the document referenced above.

MichaelG.

[Phil H 1Participant @philh1]

Yep read appendix B. Im still happy with the term dry as described by my teachers!! Appendix B appears to be talking about a surface that most definitely looks and feels dry in practice.

PhilH

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Phil H 1 on 01/11/2014 16:04:49:

Yep read appendix B. Im still happy with the term dry as described by my teachers!! Appendix B appears to be talking about a surface that most definitely looks and feels dry in practice.

.

Exactly my point

Perhaps we could put it to bed now.

MichaelG.

[Rik ShawParticipant @rikshaw]

Michael – I tried to put it to bed but it's not completely exhausted.

"With the greatest respect: I can see no evidence that you have measured the thickness of the slips."

The object of the photographic exercise was to demonstrate the thickness of the oil film using the DTI as a comparator. The thickness of the two slips is merely an irrelevance as the same two slips were used for the checks.

"Please … before replying, read Appendix B of the NIST document…………"

Why?

Rik

[jason udallParticipant @jasonudall57142]

An article I read from the 40’s indicated that slips wrung and stayed wrung if placed in a vacuum. …
..so it was not understood why ( blocks wring) then and I guess the airpressure thing was killed off ..
Me..my guess would be more to do with either micro surface texture ..nano structure like gecko’s feet.. or something to do with “quantum” effects maybe free electron migration….mmm . wonder if glass ( or other insulating material) slips would wring?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Rik Shaw on 01/11/2014 17:48:59:

Michael –

"Please … before replying, read Appendix B of the NIST document…………"

Why?

Rik

.

Because it will describe what is meant, in the context of slip gauges, by an oil film.

[the thickness of your applied oil layer is, by comparision, like the cheese in a sandwich … or whatever alternative takes your fancy]

MichaelG.

Edited By Michael Gilligan on 01/11/2014 18:45:58

[jason udallParticipant @jasonudall57142]

THIN Oil films on water are often in the order of wavelength of light..maybe 100nm.

Thats 0.1 micron…well within the range of ” precision” of slips. .(??)
About 4 micro inches…
How smooth are slips?

[Michael GilliganParticipant @michaelgilligan61133]

Jason,

According to Wikipedia:

The minimum conditions for wringability are a surface finish of 1 microinch (0.025 µm) AA or better, and a flatness of at least 5 µin (0.13 µm).

^MichaelG.

Edited By Michael Gilligan on 01/11/2014 18:57:52

[Rik ShawParticipant @rikshaw]

Michael – I think that my photos show that your "cheese" exists, I am having difficulty in understanding the point you are trying to make.

Rik

[jason udallParticipant @jasonudall57142]

So oil films are potentially of the same thickness as the upper limit on the surface finish of the slips..

And Rik.
I understand your test setup indicated the difference in indicated height between “dry” and oil filmed slips. ..
And if I read the photo right about half a 0.0005″ division.. or about 250 micro inch.
..saw no cheese
…

[Michael GilliganParticipant @michaelgilligan61133]

Rik,

My point is that there appears to be widespread confusion in this thread.

Andrew made the entirely valid point that there is an "oil film" on each surface of a "wiped-clean" slip, and that the nominal thickness of the slip is reckoned to include one of these.

I don't think that either of us has suggested applying a thick layer oil … it simply needs to be recognised that the film exists.

MichaelG.

[jason udallParticipant @jasonudall57142]

So a degreased slip would read low..ok by asmall amount but low…
Fascinating

[Phil H 1Participant @philh1]

Forgive me for laughing and I know that I contributed to this thread but Jack only asked what they are for. Bet he regrets asking.

PhilH

[Michael GilliganParticipant @michaelgilligan61133]

Just in case any Brit. is concerned by the use of NIST as the Authority … here is a page from our own National Physical Laboratory.

MichaelG.

.

P.S. … good point, PhilH.

[Rik ShawParticipant @rikshaw]

And to the OP Jack Foreman 1:

"Can someone please explain what Gauge Blocks are?
And what are they used for?"

What do you think of it so far?

Rik

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