Gage blocks on the cheap...

[TomG]

(03-28-2018, 10:43 PM)randyc Wrote: So now that the subject has come up, I'm curious about how the rest of you maintain your gauge blocks.  Any comments ?

Because I don't use them often, I clean and lube mine every time I use them. I keep a dab of light grease in the corner of the set and reapply it whenever I use a block. A rag with a bit of solvent and a swipe on the wrist works well to clean them before use.

Tom

[Vinny]

(03-28-2018, 10:43 PM)randyc Wrote: So now that the subject has come up, I'm curious about how the rest of you maintain your gauge blocks.  Any comments ?

Me? mine are in the wooden case in a drawer. Dry. The humidity in this place rarely rises above 16% and they've never developed any spots, for lack of a better word). Mine are also way older than 3 years. I've had them for probably 2 years, maybe longer, and they were probably old then. When I checked them they were within 0.001", my mic doesn't go below that and neither do my eyes! If I need to machine something closer than 0.001", I have a surface grinder for that, and still I doubt I'd get anything much closer than 0.001"!!

One thing I recall from the days when I worked making gages (grinding threads), is temperature control. All measurements were taken in a 68 degree F room (man that felt good in the summer!) and the blocks were handled as little as necessary to prevent the heat from the inspector's hands from changing the measurements.

So what was the temperature in the room when you guys made your measurements?

[randyc]

(03-28-2018, 11:19 PM)f350ca Wrote: Just how many baby's have to be squeezed to fill that bottle Randy?

Well, it's just a teeny little bottle    and doesn't have to be re-filled often.

The deviation on my chart was in millionths of an inch.  Since my capability for measurement is only .0001 up to four inches, I concluded that my gauge blocks didn't reflect the same deviations on the test data sheet by measuring the largest +/- deviations recorded on the test data sheet to see if the direction of my measurement was higher or lower, regardless of the actual measurement.

(ncidentally, the numbers on Greg's sheet are W-A-Y better than what I recall seeing on mine - I can't remember more than a half-dozen blocks with numbers in the single digits.  I'm looking at mine now and the wooden container is marked "Grade B" perhaps Greg has a higher quality set ?  (I do recall that mine was not expensive - I'm thinking less than $70, or slightly less than $1 USD per block.)

When I googled grade B gauge blocks it seems that they no longer exist, the definition was changed in 1975.  I found a couple of references to problems with cal labs because of the "grade B" markings.  A reasonable error suggested for grade B blocks was +/- 50 millionths.  My set wouldn't meet that requirement, although it wouldn't be too far off.

As an example of comparing to the test data sheet, if the TDS indicated a negative deviation of 18 millionths and my tenths micrometer indicated a positive deviation, that would be suspicious.  Although I couldn't measure 18 millionths, I could determine whether the deviation was positive or negative for many (most?) two-digit numbers.

I tried to take a good photo of this example using a .1003 gauge block.  The parallax error makes it more difficult to see  what I mean but the vernier reading is obviously less than .0004 and just slightly greater than .0003.  If the test data sheet calls this -18 millionths, I would call it a bogus number.

   

When the measured deviation trend is the opposite of the data sheet in significant samples, measured with two micrometers, then it's suspicious.  I also found several blocks that the data sheet indicated deviated by almost 75, a magnitude that I could sort-of-measure with my micrometers.  (I used both an old Mitutoyo and a new Chinese copy which has proven accurate so far.)

This is not to say that I was at any time tempted to toss the set in the garbage, LOL.  If I can't accurately measure the error, then they are more than accurate enough for me.

I've read  about the vaseline treatment before - seems like a good idea since it wouldn't rub off as readily as oil when the blocks rattle around in their container.

I live 1/2 mile from the ocean and humidity is high.  After seeing that little blotch on my .8000 gauge block I decided to keep the gauge block set and the angle block set indoors from now on.  Reading this thread prompted me to bring the blocks inside for cleaning/lubing - had I not done that, no telling what they would have looked like the next time that I actually needed one !

[4gsr]

Got lucky recently. Found a new Starrett 81 piece rectangular set of gage blocks with certs, where each gage block was checked for size and flatness. They were certified to the old Starrett A1 specification. They were calibrated in 2003. They have never been used! Still have the petroleum jelly coating on them. No scratches either! I'm afraid to use them. I gave less than $100 for them, too, from a local pawn shop.
I have two other sets of square gage blocks I use as my shop blocks. One of the sets was from a dumpster dive at one of my past jobs. I missed getting the accessory set that went with the square gage block set. Now enough for the bragging.

I have successfully recondition gage blocks removing rust and some scratches. My method uses two abrasive stones, one a new fine grit Norton indian stone such as a 1/4" x 1 x 4" lg. Second stone is a broken piece of a 1/2" square norton hard arkansas "white" stone. Use the indian stone to stone off any rust large burrs and such. Use a little honing oil or as Starrett mention, a little kerosene. Use light pressure to remove rust or burrs. It don't take much rubbing. When it get's where the stone feels like it stops cutting, stop. Clean the surface of the gage block. Next, take the hard Arkansas stone, rub it against the indian stone to make it flat against the indian stone. Now, stone the gage against the Arkansas stone, again light pressure. You'll feel when it stops cutting. Rub the Arkansas stone against the indian stone to clean and repeat rubbing the gage block. Two, three times doing this will restore the some of the mirror finish on a gage block. Won't be factory perfect or stick together when you wring blocks together, but will be close. Like others said coat the with oil or petroleum jelly for storage. I do not recommend using any general purpose grease. It can leave permanent stains from long term storage.

Ken

[randyc]

Ken, first of all NICE score on the Starretts !  Also thanks for the detailed description for cleaning up gauge blocks.

Ken or any other knowledgeable person, I have a question:

Suppose one cleaned the surface where rust is starting to form just enough to make the face smooth again but not completely removing signs of corrosion.  If the block is kept well protected with vaseline or other protective film, would that prevent any further rust or not ?

This isn't a rhetorical question, by the way, it is what I did with the gauge block in my set that showed beginnings of rust.  Thanks for any advice.

[4gsr]

(03-30-2018, 03:34 PM)randyc Wrote: Ken, first of all NICE score on the Starretts !  Also thanks for the detailed description for cleaning up gauge blocks.

Ken or any other knowledgeable person, I have a question:

Suppose one cleaned the surface where rust is starting to form just enough to make the face smooth again but not completely removing signs of corrosion.  If the block is kept well protected with vaseline or other protective film, would that prevent any further rust or not ?

This isn't a rhetorical question, by the way, it is what I did with the gauge block in my set that showed beginnings of rust.  Thanks for any advice.

Randy,

Can't guarantee it won't come back. It'll always be stained where the rust was located.  Keeping the block coated with vaseline or oil or other protective film should keep rust from coming back.  Have to remember, rust does remove a layer of atoms or so off the surface.  Nothing you can do about replacing it.  To remove the stain from rust, it has to be sent to a lab and the surface re-lapped, which will change the size considerably.  Maybe by couple thousandths or so.  By the time you do all of that, your better off buying a new gage block. 

Please don't use Evapo Rust or any other home brew solution to remove rust on gage blocks. 

Ken

[randyc]

I used a green dish-scrubbing pad dipped in mineral spirits and rubbed the block with it until a white tee-shirt didn't pick up any color when wiping the block vigorously.  Yes, you're right, the stain is still there and always will be but I'm hoping it doesn't spread.

I was very fortunate because:

(1)  The rust spot was on only one of the eighty-one blocks
(2)  The rust spot was on one of the edges, not on either of the gauge surfaces

Many thanks, Ken, I appreciate your comments !