Storing micrometers and calipers

Avsfan135 · Mar 8, 2011

Ok here's a stupid question

I was told not to store calipers and 0-1 micrometers closed all the way and to leave them open a little.

I never thought anything of it I was just learning and naturally just trusted the guys that told me that.

So I pass this information on to the new guy I'm trying to train. He just got his new tools. However, he didn't just listen he wants to know why?

Well I don't know exactly so I looked for some info on it and couldn't find anything.

What are your thoughts? Do you keep tools open closed does it matter??

Thanks guys

RC99 · Mar 8, 2011

I can think of two reasons.... Firstly, when then are closed they are stressing a frame somewhat..

Secondly before micrometers had carbide faces they were hardened steel... When you bring two pieces of very flat steel together they will cold weld together over time... Just like gauge blocks will if wrung together for days...

Whether carbide cold welds I will leave that up to the more knowledgable here..

Clive603 · Mar 8, 2011

I was told that storing them closed promotes corrosion between the faces and, if the faces are dirty, contamination can glue them together. Followed immediately by "If I catch you putting mikes and calipers away without cleaning the faces I shall fetch you such a clip round the lug'ole." Also advised to put apiece of anti rust paper in the box and change it every year. Another one I've heard was that storing mikes closed tends to squeeze out the lubrication film from the screw. Open and, presumably unstressed, lets the film re-form.

My guess is there is no real hard info about this. More a case of doing what seems right and avoiding any possibly conceivable pitfalls whether real or not. Also in keeping with general practice like releasing the tension on a hacksaw frame when you put it away.

Usually a simple general rule is easier than 'undreds of exactly right specific ones even when the general rule isn't quite necessary. Six hundred and umpty eight billion lawyers and bureaucrats may disagree.

Clive

tailstock · Mar 8, 2011

When I bought a new set of mics a note in the box said not to leave them with the anvils tight to each other, more chance of stress and its hard on the thimble.

Avsfan135 · Mar 8, 2011

Clive603 said:
a case of doing what seems right and avoiding any possibly conceivable pitfalls whether real or not.

That's how I feel!

Thanks guys I'll pass this along to him

The real Leigh · Mar 8, 2011

Leave them open

It's not only "tightly" closed that poses a problem.

If they're "almost" closed, capillary action can bring moisture in between the faces that leads to corrosion.

Leave them open by a visible amount, like .05" or so, and you won't have a problem.

- Leigh

Forrest Addy · Mar 8, 2011

Storing precision tools and measureing equipment aint rocket science.

Persnickety ways of storing measureing tools really doesn't matter except to purists and folks who like to buffalo noobs. It's probably not a good idea to close an 0-1 so it stresses the frame but otherwise store them where it's clean and dry.

If the mike(s) have to be stored or ignored for a period of time they should be coated with a good preservative oil (most any will do so long as it's not WD40) and stored in an enclosed place. If there is any concern about humidity, place a charged bag of dessicant with the mikes or any other precision equipment for that matter.

Come to think of it a shrewd fellow should have an annual event where he dismantles, cleans, adjusts, and calibrates his measuring equipment. I generally devote the week between Christmas and New Years for that. Not much happening anyway and it is a good time for annual reflection of past events and future plans. Simple, careful, non-strenuous work is a good setting for that sort of thing.

Mark Rand · Mar 9, 2011

Forrest Addy said:
Come to think of it a shrewd fellow should have an annual event where he dismantles, cleans, adjusts, and calibrates his measuring equipment. I generally devote the week between Christmas and New Years for that. Not much happening anyway and it is a good time for annual reflection of past events and future plans. Simple, careful, non-strenuous work is a good setting for that sort of thing.

Although it could be a bit of a game for some folks to get their shop up to a nice steady 68°F for the calibration work at that time of year :crazy:

Regards
Mark

ietech · Mar 9, 2011

heat

Forrest Addy said:
Storing precision tools and measureing equipment aint rocket science.

Persnickety ways of storing measureing tools really doesn't matter except to purists and folks who like to buffalo noobs. It's probably not a good idea to close an 0-1 so it stresses the frame but otherwise store them where it's clean and dry.

If the mike(s) have to be stored or ignored for a period of time they should be coated with a good preservative oil (most any will do so long as it's not WD40) and stored in an enclosed place. If there is any concern about humidity, place a charged bag of dessicant with the mikes or any other precision equipment for that matter.

Come to think of it a shrewd fellow should have an annual event where he dismantles, cleans, adjusts, and calibrates his measuring equipment. I generally devote the week between Christmas and New Years for that. Not much happening anyway and it is a good time for annual reflection of past events and future plans. Simple, careful, non-strenuous work is a good setting for that sort of thing.

Not really Persnickety -- If you consider thermal expansion and contraction amongst several other things mentioned in previous posts it takes little time or effort to follow the direction provided with your measuring instruments -- really it's easy.

Expansion and contraction is ALWAYS a comsideration with most anything, especially precision tools.

Metal weakens and stresses if it is under load during the expansion contraction process. 110 deg what happens to a 0-1" mic or any mic or caliper tightly closed at this temp especially if you closed it tight early last morning at 60 deg.

I might be way off but I don't think so --- hey tighten 'em up what the heck does the manufacturer know anyway. :cheers:

Forrest Addy · Mar 10, 2011

Cleaning and tuning up precision tools is a nice comfy job to do in front of the TV. It's a little awkward for height gages and other large stuff but a lap and a small table in a warm room make a pretty good work station for mikes and indicators. A bottle of lighter thinner, a squirt bottle of household cleaner, Q tips, tooth picks, a tooth brush, little screwdrivers, pliers, tweezers, wipes, 3-in-1 oil, a muffin pan for parts, and other stuff all fit on a plastic cafeteria trey. Needless to say anything shedding crumbs, grease, or salt is verboten.

The actual physical measurement part has to be undertaken with a little more care. You don't really HAVE to have 68 degree environment. Any constant temperature in a non-condensing environment will do provided the appropiate corrections are made to account for instruments having non-ferrous parts. I do that stuff at the kitchen table usually wearing white cotton gloves to limit heat migration from my hot little hands.

adammil1 · Mar 11, 2011

I thought the answer to this one was simple and what others have mentioned. I was always told it is due to differences in thermal expansion of different materials. If you tighten the things down all the way at one temperature, put them away and the temperature changes you could have troubles.

Is this not the real answer? At least that is what I have been told by several machinists who have taught me over the years. In fact I can't say for sure but 6-7yrs back when I toured Starrett I believe they told me the same there too.

Bruce Nelson · Mar 11, 2011

It's simple. If you leave the mike faces in contact, humidity can wick itself between the spindle and anvil faces, and cause corrosion on these faces. Particularly if left over a number of years.

The same principle applies with gage blocks. You should never store them wrung together, they should be disassembled and stored separately in their box.

Test question: What principle allows the wringing together of gage blocks?

(a) Magnetism (b) Vacuum (c) Perfectly flat surfaces (d) None of the above (e) Ask Gordon B. Clarke

Lord Byron

doug8cat · Mar 12, 2011

I do believe Gordon has found a singularity

I keep all of precision metrology equipment in a cabinet with "golden rod". A golden rod can be purchased at any gun shop or sporting goods store. You simply plug it in place it in the closed cabinet and it will emitt a low level of heat thus keeping the humdity to a bare minimum. Since I introduced its use in my metrology cabinet I have had no problem with humity what so ever. Mind you the cabinet must almost air tight, as these devices cannot remove large ammounts of water. As to the temp they produce I'm not sure, come to think of it I gonna place a thermometer in their right now.

Excuse me.

P.S. As far as keping mics open it was drilled into my thick skull years ago by several people. It is one of those simple things you just do.

Bruce Nelson · Mar 12, 2011

I wanted to make a snide, clever comment; but the possibility of future regrets said no.

Lambert · Mar 12, 2011

Bruce Nelson said:
Test question: What principle allows the wringing together of gage blocks?

(a) Magnetism (b) Vacuum (c) Perfectly flat surfaces (d) None of the above (e) Ask Gordon B. Clarke

Lord Byron

None of the above if we`re being fussy....

The principle at work is Van der Waals force , also kown als the force holding molecules together in a material.
The very flat surfaces of gageblocks enable enough molecules of the 2 blocks to get close enough together to notice Van der Waals force between 2 separate objects.

Bruce Nelson · Mar 12, 2011

Lambert scores 100. I quote from the article by Dave Friedel, General Manager of Starrett's Webber Gage Division:

"The sources of the forces holding gage blocks together are thought to come from:

1.)Air pressure from the surrounding environment as the air is squeezed out when the blocks are slid together.

2.)Surface tension from oil that remains on the gage blocks or water vapor from the air acts as a glue to hold them together.

3.)When two very flat surfaces are brought into such close contact with each other, this allows an interchange of electrons between the atoms of the separate blocks, which creates an attractive molecular force. (This force will remain even in a vacuum or if no oil or water is present on the blocks.)

The last two sources are thought to be the most significant."

Note that this has nothing to do with magnetism. Apparently this would work if the gage blocks were made of glass or ceramic.

The real Leigh · Mar 12, 2011

Lambert said:
The very flat surfaces of gageblocks enable enough molecules of the 2 blocks to get close enough together to notice Van der Waals force between 2 separate objects.

Interesting idea, except...

The faces of gage blocks don't come together. They're separated by a film of lubricant. It is the effect of that fluidic interface that provides most of the binding force between two gage blocks.

Quoting from "Appendix B Wringing Films" of The Gage Block Handbook (NIST), beginning on page 138:
"2. There is some metal-metal contact between the blocks, although too small for a significant metallic bond to form. Wrung gauge blocks show an electrical resistance of about 0.003Ω [B3] that corresponds to an area of contact of 10-5 cm2."

"4. The fluid between blocks seems to provide much of the cohesive force. No matter how a block is cleaned, there will be some small amount of adsorbed water vapor. The normal wringing procedure, of course, adds minute amounts of grease which allows a more consistent wringing force."

Bruce Nelson said:
Apparently this would work if the gage blocks were made of glass or ceramic.

Gage blocks are available in ceramic from all major manufacturers.

- Leigh

The Gage Block Handbook can be downloaded from http://www.nist.gov/calibrations/upload/mono180.pdf

gorrilla · Mar 14, 2011

Bruce Nelson said:
I wanted to make a snide, clever comment; but the possibility of future regrets said no.

I have no idea what you were going to say, but that "possibility of future regrets" is what some folks call "wisdom".

gorrilla · Mar 14, 2011

The real Leigh said:
Interesting idea, except...

The faces of gage blocks don't come together. They're separated by a film of lubricant. It is the effect of that fluidic interface that provides most of the binding force between two gage blocks.

Quoting from "Appendix B Wringing Films" of The Gage Block Handbook (NIST), beginning on page 138:
"2. There is some metal-metal contact between the blocks, although too small for a significant metallic bond to form. Wrung gauge blocks show an electrical resistance of about 0.003Ω [B3] that corresponds to an area of contact of 10-5 cm2."

"4. The fluid between blocks seems to provide much of the cohesive force. No matter how a block is cleaned, there will be some small amount of adsorbed water vapor. The normal wringing procedure, of course, adds minute amounts of grease which allows a more consistent wringing force."

Gage blocks are available in ceramic from all major manufacturers.

- Leigh

The Gage Block Handbook can be downloaded from http://www.nist.gov/calibrations/upload/mono180.pdf

Something that's always fascinated me (I know, I'm easily amused), is the idea that two pieces of similar metal could be polished so well as to induce a "molecular bond" between them. Any thoughts?

Bruce Nelson · Mar 14, 2011

Let it go, Gordon.

Storing micrometers and calipers

Cast Iron

Diamond

Titanium

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Cast Iron

Diamond

Diamond

Diamond

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Titanium

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Titanium

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Hot Rolled

Stainless

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