An utter lack of standards..micrometer, that is.

MrChurchill109 · Jun 6, 2008

In my purchases of lots of machine tools over the years I've managed to acquire a set of very nice micrometers up to about 4 inches or so. Being very old (most old B&S with the occasional Starrett) and long out of their original boxes none of them came with either the setting tools or standards.

Now the setting tools are no big deal - but how to make standards? I could simply use the next micrometer down to each to make a standard for the next (0-1" to make a 1" standard for the 1-2" mike, 1-2" to make a 2" and so forth) but seems to me there I could easily end up with stacking tolerances and lose some accuracy by the end of the process (not that I'm terribly concerned about these old guys having .00001 repeatability).

Yes, gauge blocks would be the way to go - but I don;t have the cash for them right now.

SO - talk to me folks - anyone got a good idea here?

moonlight machine · Jun 6, 2008

watch e bay for some gauge blocks, if your not in a hurry you can get a set pretty cheap

The real Leigh · Jun 6, 2008

Micrometer standards are called "setting rods" or calibration rods or similar terms. They're 1/4" diameter x the nominal length. You'll find them with flat or radiused ends, the latter being on the radius of the sphere with the nominal diameter.

McMaster-Carr www.mcmaster.com shows them on catalog page 2214 for around $20 each, from 1" to 14" in 1-inch increments.

- Leigh

hesstool · Jun 7, 2008

Leigh has the best suggestion so far. I've seen Starrett setting rods sell from $18 to $25 new in the range you need.

The real best thing would be a master micrometer calibration set, but that would set you back at least $800 for a 1-6" range.

If you want a quality set of gage blocks, by all means hold out for a nice set of Webbers. If you don't mind buying Chinese, Rutland has an 81 piece set on sale now for $49 . :vomit:

jim rozen · Jun 7, 2008

I have a lack of standards of the one inch-ish range. However in a
box of stuff I aquired at one time, there was a carbide block with flat faces
and nice radiussed corners.

That has become my standard for 1-2 inch micrometers, it isn't an even inch,
it's 1.3something.

Jim

Greg Menke · Jun 7, 2008

I would immediately go buy a small & cheap set of gage blocks, maybe a 9 or 30 piece set- with the understanding that they're probably not really flat, the cert is almost certainly worthless and they are probably only good to a tenth. Then test all your measuring tools against them, you may find a few surprises. Its worth making a few different length stacks to test your tools at different measurements. It'll also reveal how accurate your feel is for setting the tools.

Meantime start searching around for a good set, or go for the pricey micrometer calibration set as said.

I don't think theres much point in getting a big set of the cheapo blocks, if you need a big set then get good ones.

Greg

jim rozen · Jun 7, 2008

As mentioned, micrometers are not just supposed to be checked at the extremes of
their travel. It's also important to check the linearity of the tool. One way is to
check many points over the screw length, and also many points over one turn of the
screw.

Jim

PeteM · Jun 7, 2008

I've made a micrometer standard with radiused and hardened ends cut from 6" drill rod (to complete a set) but it took an hour and you still need a precise reference. The hard part is sneaking up on the dimension by lapping the ends -- though you can always mark the rod if it is a bit under or over. I did this to match up the appearance on an otherwise complete 1-12" set -- but wouldn't do it again.

As noted above, Ebay is your friend. You should be able to buy a complete set of mic standards for under $40 or so, and a partial set of gage blocks for under $20 or so. You don't need a complete set -- just a fair sampling of blocks to get you in range.

The micrometer standards, incidentally, will turn out easier to use. Also, be sure to carefully wipe the anvil ends on your micrometer -- it's easy to have several tenths of oxidized oil etc. there.

beege · Jun 7, 2008

Balls (like ball bearing balls) are made to pretty tight tolerances. They are also good for double-checking the parallel-ness of the faces, when you measure in different places. If you need to get them calibrated, it's short money. Send them to a calibration house and get them certified to a few millionths of an inch

hesstool · Jun 8, 2008

beege said:
parallel-ness of the faces

Sorry Beege, I'm going to have to call you on this one. I think parallelism would be more appropriate.

I probably would've let this slide, but since I recently heard an engineer instruct me to keep the "ovularity" of a bore to a minimum, I'm a little hyper-sensitive.

tdmidget · Jun 8, 2008

hesstool I'm with you. Precision is our business. Our words should be as precise as our work. Uh-Oh. I just realized that maybe their words ARE as precise as their work. Scary, huh?

beege · Jun 8, 2008

I guess I've listened to too many Bush sound clips. It was a long say yesterday, and I wasn't thinking clearly.

Also thought of parallelicity, but that sounded just.... wrong. I know parallelism, but it wasn't in my head at the moment.

Damien W · Jun 10, 2008

beege said:
I guess I've listened to too many Bush sound clips. It was a long say yesterday, and I wasn't thinking clearly.

Also thought of parallelicity, but that sounded just.... wrong. I know parallelism, but it wasn't in my head at the moment.

It's lucky that you didn't think of "ovularity" either. It has connotations of ovulation and I don't think hesstool had that in mind. Maybe concentricity or cylindricity or even ovalarity?

Tdmidgit I wish more would adopt your views on accurate description. I get the impression that it is a national characteristic to generalise.

So, for accuracy's sake you need to extend your vocabulary to include adjectives like a smidgen shorter or longer (as the case may be). Of course "gnat's whisker" may be substituted for smidgen if they are more numerous and familiar in your locality. When descriptions favour fractional language then a poofteenth might come into play.

jim rozen · Jun 10, 2008

I think optical flats are used to check the parallelism
(ovularity????

) of micrometer faces. Basically
you look at the fringes under a monochromatic light source.

Jim

The real Leigh · Jun 10, 2008

jim rozen said:
I think optical flats are used to check the parallelism
(ovularity???? ) of micrometer faces. Basically you look at the fringes under a monochromatic light source.

Hi Jim,

That's correct.

Mitutoyo makes (made?) a micrometer calibration kit that contained a set of gage blocks and an optical flat. I can't seem to find it on the web at the moment, although there's one on evilpay item 250252639323. It's up for another 5 days.

Looks like this.

- Leigh

hesstool · Jun 10, 2008

Damien W said:
It's lucky that you didn't think of "ovularity" either. It has connotations of ovulation and I don't think hesstool had that in mind. Maybe concentricity or cylindricity or even ovalarity?

I did have that in mind. That particular engineer was really asking for Cylindricity but the word Ovularity spewed out of his mouth. He honestly thought nothing was wrong with word Ovularity to describe an out of round condition in a bore. :rolleyes5:

Being the wise arse that I am, I told him to take his part to the first female machinist he finds and maybe she could do it for him.

The real Leigh · Jun 10, 2008

hesstool said:
That particular engineer was really asking for Cylindricity but the word Ovularity spewed out of his mouth.

I believe he was seeking "ovality" in vain.

- Leigh

hesstool · Jun 10, 2008

The real Leigh said:
I believe he was seeking "ovality" in vain.

Not doubt. But I still won't let him off the hook for saying it.

jim rozen · Jun 11, 2008

Maybe his wive was ovulating at the time....

Jim

Damien W · Jun 11, 2008

Jim got that one wrong too.

It's one wife or two or more wives if you live in Utah.

I heard more than once on a recent TV news item one or more Yanks say compensory or something like it. Is that meant to be an adjective form of "compensation"? The trouble is learned gurus in english grammar and language will start to say that it is in common usage and then try to legitimise it.

An utter lack of standards..micrometer, that is.

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