Gauge Blocks

I'm just glad that I don't have a set of gauge block and have to spend half the day deciding what rag to wipe them down with each time I use them.

No wonder we get so little posted in the Work in Progress section of the forum

J

Oh dear, I've got two sets, imperial and metric; but that's not the reason I don't generally post in the Work in Progress thread.

Andrew

If anyone has a technique for completely removing the layer of oil from metals I would be pleased to hear it. I have tried to remove the last mono-molecular layer when I worked on food and pharmaceutical packaging, but without success.

Any tips, the nearest we have come is washing in toluene followed by ultrasonics , using water borne and solvent borne methods. Unfortunately the water miscible systems involve wetting agents which themselves leave behind a film.

Jerry

All very interesting comments.

When working in the Met lab the slip gauges were used to check and calibrate Go & No go gauges for production purposes. Now what we are talking about here is a temperature controlled room where both the slips and the gauge being checked were placed in a ultrasonic vapor degreaser filled with freon 13 and then wiped clean with a disposable cloth. now if there was any oil left on either component after that it was so insignificant to even guess.

After use they were wiped with an oily rag to remove any human skin acid and placed back in the box for storage.

I agree with Andrew about his thoughts on Nitrogen getting between the blocks without an oil film but wring two of these blocks together and try pulling them apart, With master blocks you will not succeed.

Also optical flats which are used to check the blocks do not have any oil film on them and you have to ware special gloves to handle them. they are made of special optical glass or quarts crystal. place them on the surface being checked and switch on the sodium light and you will see black rings where there is any ware.

But to get to the point the amount of oil on the surface would be so insignificant it is really not worth talking about. Now don't forget temperature plays a big part and I dought if you will ever use or see gauge blocks outside a Met room.

Larry

Edited By Larry Coleman 1 on 09/01/2015 09:54:40

At the risk of collectively losing the will to live, IIRC the Van Der Waals forces can be sufficient to provide significant cohesive forces between (sufficiently) smooth parallel faces. In the extreme it is possible to join surfaces of similar material without the need for adhesives. The force is inversely proportional to the cube of the distance and obviously also proportional to the area. The "weak" VdW forces are more long range than the direct interatomic forces holding the atoms together.

Microscopically, the surfaces of even the finest pair of gauge blocks will be fairly rough but with enough surfaces in close proximity to generate some degree of VdW pressure. There is clearly some gap size at which they begin to come into effect and it looks as if the very fine end of the gauge block quality range (master blocks?) may be in that zone. The effective gap will be a function of the surface roughness and the residual crap (oil etc) left on the surfaces. Of course, if the surfaces are not almost perfectly clean, there will be surface tension and other effects resisting the wringing movement as a result of oil and contaminants.

Sitting in my armchair with my flak jacket on...

Oh No! Not van de Waals forces! There has been much correspondence amongst physicist disputing the existence of these. Perhaps we should all back-off until we have read the latest research papers, Then we might be able to take a view.

For the uninitiated these forces have been in dispute for at least forty years.

Jerry

You'd better write to all the schools and universities around the world to let them know then, as it's been taught for many decades - and continues to be. When in Rome...

Merry

I bow to your greater knowledge.

Jerry

I bow to your greater knowledge.

Jerry

> van de Waals force

Eye Level?

Lets tryagain

In summary.

Even in the 1920's this was being debated.

The practical " result" was how much does the oilfilm effect size..

From the table above table

Sixteen 1/8" slips were compared to one 2" slip

Parrafin error -0.00001918

Vasleine error -0.00001914

Lubricating oil error -0.00001906

No film.. error -0.00001887

It was noted with no film noticeably less wring was observed..

..

Source npl circa 1922

Now it looks like the stack might be low relative to the 2" slip..

And we have a var of 0.00000010...inch..( 1 x10^-7 ) (0.1 micro inch) from oils one to another...

That ought to be good enough for model makers at this scale

Now since the practice was to wring the blocks to the surface plate..we have one layer in the case of two slip and sixteen in the case of the stack... But if the manufacture of the slip includes thickness allowance for the oil film...oh hell who cares!...

The physics of what is the origin of the wring force intrigue s me but it appears to one way or another matter little to use. 

Personally I would get the slip as dry as possible for use and re oil before storage.

Edited By jason udall on 09/01/2015 16:59:10

Edited By jason udall on 09/01/2015 17:05:08

Jason

I think we must accept we do not live in a perfect world. Don't forget the atmospheric humidity and as minute as it is it would condense on the surfaces. In the Metrology room the operator wears gloves and at times we donned the mouth mask made of cotton like a brain surgeon to prevent fogging up the surfaces. Now we really were splitting the atom in my opinion.

Now I think that none of us will ever use this type of equipment in model making and I have only seen a gold yard stick once in my life. I wonder if they still exist. It is interesting to wonder if engineering today is still advancing or has our diligence for perfection been lost...

It is exciting to talk to you guys and as a dinosaur of engineering development I have forgotten more than I have learned in the last ten years but I am still learning. I still wonder around the university labs here and build scientific equipment as a volunteer. And some of the Ph.D.'s look at me funny when I say, well lets build a device for that experiment. I built an X ray machine for them but the perils of being able to run it destroyed that unit. Government licenses & WH&S became to expensive.

Take a good look at the three D printer what is it? In fact its a 3D pantograph in reverse. In stead of removing the unwanted material and leaving the target reproduction. We only place the wanted material on the table.

I might start a new thread. Forgotten engineering techniques, Because it is our obligation to pass them on.

Theres a few topics to throw around.

Larry

.... ho hum back to back to 'KISS' mod. eng..  I bow to your greater knowledge...

George

Edited By mechman48 on 10/01/2015 10:20:34

Well, they certainly existed 50 years ago when I studied physics at university although it has only recently become possible to measure them. Of course the theory has been disputed. That's science. If we accept everything as true we don't progress.

Try telling the geckos that the forces don't exist and they'll all fall off the glass of their vivariums!

Russell.