Gauge block care and useage

On Sat, 11 Mar 2006 01:01:24 -0800, "Harold and Susan Vordos" wrote: SNIP A BUNCH

Hey Harold,

If Robin takes you up on your offer, I'd like a peek at it too, Thank You.

snipped-for-privacy@ciaccess.com

TIA

Take care.

Brian Lawson, Bothwell, Ontario.

On Sat, 11 Mar 2006 01:01:24 -0800, with neither quill nor qualm, "Harold and Susan Vordos" quickly quoth:

That sounds like an interesting upload for the Dropbox, Harold.

-- As a curmudgeon, I grok that in its entirety. --LJ

My inquiring mind want's to know....

In general, what sort of temperature differentials are acceptable when working to those tolerances on measurements of a few inches or so with common metals?

ie, do you have to worry much about the body temperature of your hands affecting parts or instruments.,

Jeff

I'm Calling BULLSHIT !!!!

Care to expand a little on the statement?

Perhaps with a quote of exactly WHAT you are calling bullshit upon.

Cheers Trevor Jones

On what???

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Hmmm...reading this thread has me wondering...

My uncle was a machinist at an aircraft factory during WWII. As a kid growing up after the war, I spent a lot of time in his shop learning things at the age of 6 or 7 that most don't learn until their collage years. One of my tasks in his shop was the care and storage of gauge blocks. The following is what my uncle taught me along with some questions about the techniques:

Gauge Block Cleaner/Preservative: Use Sewing Machine Oil. Do not substitute.

Question: Out of all the lubricants available, even 50+ years ago, why sewing machine oil? HAZMAT info says sewing machine oil is pure "mineral oil". My observations are that medical grade "mineral oil" for internal consumption purchased at a pharmacy does not evaporate. Sewing machine oil does. Are they different?

Cleaner/Preservative Remover:

200 proof Industrial Ethyl Alcohol. Do not substitute. Keep container tightly closed.

Question: Why not Methyl Hydrate or Isopropyl (rubbing alcohol)? They are solvents also. These would be much less hassle to get.

Tools: Camel Hair artist's brush Surgical grade cotton batten. Roll of 3" wide surgical gauze Saucer from kitchen.

Preparation for Use:

- Pour ethyl alcohol into clean saucer from kitchen

- Place gauge block into alcohol

- Use camel hair brush to thoroughly clean off oil from gauge block

- Place gauge block on strip of clean surgical gauze to dry at room temperature for at least two hours before use.

Preparation for Storage:

- Tear off a 1 inch cube of cotten batten

- Apply 10 drops of sewing machine oil to cotten batten

- Rub gauge block gently but thoroughly with oil soaked cotten batten until it glistens with oil. Replace cotten batten if it shows any signs of dirt.

- Place oily gauge block into storage case.

Any comments on the above? I've been doing it this way for years. My gauge blocks I've inherited from my uncle seem to be in good shape and and have no problems with wringing. Are gauge blocks now made from different materials than they were 60+ years ago that now require different cleaning/preserving techniques? Or, are all these fancy spray cans of cleaners and preservatives just a manifestation of our modern society?

The spray cans really represent an easy way to get a product that is packaged to do exactly what is intended. I figure that what works, works, and your method seems to be working for you.

Gauge blocks ARE available in different materials these days. Ceramic and carbide are out there as well as plain old steel. The new materials are a bit less heat affected and not subject to corrosion, but are more expensive, too.

Cheers Trevor Jones

Of course, the crazy thing is that steel may often be the best choice... because the most common materials used are steels, gauge blocks that have similar coefficients of thermal expansion (is. steel) reduce the need to take measurements at a specific temperature.

Mark Rand RTFM

The .0001" work I used to do was done in a shop with no temperature controls, but keep in mind that the work was very small, so the temperature differential was less of a concern than it would be on larger items. Good sense is a part of success-----allowing for expansion when necessary, or cooling parts and instruments to an acceptable level.

On larger items, temperature can be a serious factor. Case in point: I ran an order of spacers, quantity of 630, for the main landing gear on a C-130. The spacer was about 6-3/4" diameter as I recall. I still have one somewhere in storage, but don't have a clue where it is. It was made from

7075-T6 aluminum tubing, and had a 1" corner radius that went into a 7 degree taper. The part was turned on a lathe with a hydraulic duplicator. There was a straight portion of the spacer that was held to +/1 .001", about an inch long. For finishing cuts, the properly roughed parts were introduced to soft jaws that were warm from heat from the headstock, so the parts expanded as they were machined, in spite of a small supply of coolant being applied. In order to end up with a straight turn, the template was dialed in with a slight angle, about a half thou as I recall, so the finish machined part was straight. The angled template compensated for the ever growing part. It goes without saying that the timing in running the parts was critical----otherwise the expansion wasn't in lock step with the template setting.

Typical grinding tolerance was usually .0002", which we accomplished in the shop with no particular care aside from general shop methods. Temperature swings in precision grinding are generally not very wide, due to almost all operations being run under flood cooling. The huge volume of coolant in the machines tends to keep the temperature stable.

As for the ring gauges with the .000020" tolerance, the parts were inspected for size at the machine by a second (unbiased) party, then were required to sit in the gauge lab for 24 hours before being certified. Temperature and humidity are both important. The gauge lab was kept at 68 F as I recall, but I have no clue of the acceptable level of humidity.

Bear in mind that our normal work did not require holding such tight tolerances. The set of ring gauges was an anomaly, due to an immediate need that could not be met commercially. The rings were sized on a standard, manual, Sunnen hone. The hone is more than capable, but it requires skillful application.

Harold

Steel moves at about .000006 ( six millionths) per degree per inch length. On a ten inch ring or rod a ten degree change will move it 100x .000006 or .0006.

A 30 degree change will move it .0018 inch.

The trick is to run enough coolant so the part does not heat up and wait for the part to assume room temp. before you make the finish cut. If your measuring tools are kept in the same temp. conditions as the part, they will pretty much compensate for a variation in temp from the standard temp of 68 degrees F.

John

I have a master set of gauge blocks that only get held with cotton gloves. The acid oils from your hands will eventually cause stains on the blocks.

At least uf you see fingerprints on the blocks you can find out who done it.

John

No doubt. My email is screwed up at the moment. Anyone know how to get the tool bar back up on IE?

Still wondering how I missed that , but at least someone caught it.

I've asked hal and this is the most he'll tell.

I did a flat six crank shaft once for fun to .00003" and the inspection guy was flustered like his own tools where off. I got a good laugh watching from a distance.

FWIW, I was taught to apply "nose oil" to gage blocks before wringing. Just rub a finger down your nose and smear a film on the blocks. I was also told once that when clean blocks are wrung together the two blocks actually share electrons which causes them to stick so well. Not sure about that. Randy Replogle

Your "preparation for use" corresponds to a machinist explaining the proper use of gage blocks to me in an aviation environment. He was using acetone versus alcohol though, and then making sure not to touch the mating surfaces afterward because the oil from the skin affects final size.

Based on an incident that happened several years ago, I've avoided drugstore "mineral oil" for any sort of technical application.

We had a manifold with several high pressure transducers mounted on it. We were gathering data for temperature compensation tables. We would apply a specific pressure with a deadweight tester then vary the temperature of the transducers in a thermal chamber while logging and plotting the outputs. We were using "mineral oil" as the working fluid.

I got a call at 9pm from the project leader. He said all the transducers had died at -30 degrees C. As we were far behind on this project and it was a make-or-break project for the company, I came in immediately.

It didn't take me long to find that there wasn't anything wrong with the transducers, but that at

-30 degrees C, the mineral oil had changed consistency to something more like a cross between slush and Vaseline. Rinsing and refilling the system with Mobil1 5W10 (the best thing I could find nearby at that time of night) fixed the problem.

So what's in mineral oil? Water? I don't know. I just don't like the stuff any more.

Blocks should be wrung perfectly dry. If they won't, there's a problem with one of them, maybe both. Anything applied to blocks will change the overall size, albeit only a few millionths. That defeats the purpose of gage blocks, particularly if a stack is developed with several small blocks.

The idea of a miniscule film changing size appreciably was driven home for me when the QC department had requested a dial indicator that was mounted on a steel pin, which, in turn, would be inserted in a bore and spun as a concentricity check against another surface. It goes without saying that the fit, in order to work properly, had to be barely a slip, nothing more. Diameter was about 1" (this was back in the early 60's, so my memory has faded) and maybe 3" long. The only way to judge size for this particular job was to fit the bore to the existing pin. I was shocked when I was attempting to mate the parts while they were still wet from honing and they wouldn't go, although they seemed to want to. With the parts washed in solvent and air dried, they fit perfectly, but so much as finger prints prevented the fit. Very sobering.

Harold

That is good to know. I'll have to experiment to see how well acetone removes the sewing machine oil that I use. Thanks for the tip.

Ok here it is from my Metrology book from Mitutoyo.

"The clean>