Measure a stubby diameter next to a large face

RJT · Jul 21, 2020

Can't get a regular set of mics on this diameter. Calipers are fine for rough turning, but grinding this diameter .5900 - .5902 " after heat treat , I will need a way to get a mic on it preferably while between centers. Large diameter 2.283, diameter to measure is only .196 long. Is there an off the shelf micrometer that can do it?

Milland · Jul 21, 2020

Something like this might do it: https://www.mscdirect.com/product/details/06233670 , but I'd want a higher level of precision if you're trying to control within two tenths.

Would a high-accuracy test indicator (at least .00005 reading) on a pivoting frame with a contact roll underneath the tip work for you? You'd have to control approach (ideally on a linear slide), and set the reading with X-class gauge pins for high/low tolerances. Frequent rechecks would be needed to insure good readings.

Other than that, contact Marposs or one of the other in-process gauging companies. In Process Measurement and Positioning on External Cylindrical Grinder | Marposs

But now you're talking some bucks...

Mike1974 · Jul 21, 2020

Milland said:
Something like this might do it: https://www.mscdirect.com/product/details/06233670 , but I'd want a higher level of precision if you're trying to control within two tenths.

Would a high-accuracy test indicator (at least .00005 reading) on a pivoting frame with a contact roll underneath the tip work for you? You'd have to control approach (ideally on a linear slide), and set the reading with X-class gauge pins for high/low tolerances. Frequent rechecks would be needed to insure good readings.

Other than that, contact Marposs or one of the other in-process gauging companies. In Process Measurement and Positioning on External Cylindrical Grinder | Marposs

But now you're talking some bucks...

I first thought blade mics, but a 1" would probably not reach (.800 side roughly), unless you were willing to modify it?

That said, not sure I would trust much of anything other than an indicator, or digital/laser (ish) something to hold +/-.0001" :eek:

michiganbuck · Jul 21, 2020

Surface grind a go /no go gauge.
Part and gauge need be at given test temperature. .

A .500 nose machine center might allow a micrometer to get in..My old German indicator micrometer could measure that

AJ H · Jul 21, 2020

Disc Micrometer?

Milland · Jul 21, 2020

AJ H said:
Disc Micrometer?

That could fit, but OP is trying to control to a couple tenths - I'd not trust a disk mike measuring just one side with that level of accuracy.

BobM3 · Jul 21, 2020

Make the stubby diameter long enough to measure in machine. Final operation would remove the extra length.

RJT · Jul 21, 2020

30 pcs so Marposs is out. A custom made gage that holds an indicator that we can make in house looks like my best option. Part is heat treated so removing extra long tail not a good option.

AJ H · Jul 21, 2020

Milland said:
That could fit, but OP is trying to control to a couple tenths - I'd not trust a disk mike measuring just one side with that level of accuracy.

I agree, but that's what he asked for, and I see it happen a lot. That's something of a rub for me is how freely people talk about holding tenths. Yet use traditional mic's and shop floor grade CMMs in unperfect climates. If they hit tolerances in that situation it's on accident. Confusion between accuracy and resolution is the problem. However it's the age old "how does your customer measure it?" probably with the same crap, and the cycle continues. I realize there's a lot of high end equipment in the world but I'm convinced most job shops function this way.

Gordon B. Clarke · Jul 21, 2020

RJT said:
Can't get a regular set of mics on this diameter. Calipers are fine for rough turning, but grinding this diameter .5900 - .5902 " after heat treat , I will need a way to get a mic on it preferably while between centers. Large diameter 2.283, diameter to measure is only .196 long. Is there an off the shelf micrometer that can do it?
View attachment 294559

Maybe, just maybe, 2 jo-blocks (2 x 1"?). One against the anvil of a very good (as in accurate) micrometer and the other against the micrometer spindle? When you take a part out of the machine measure again and see if you still get the same result. If yes then maybe good to go?

AARONT · Jul 21, 2020

Gordon B. Clarke said:
Maybe, just maybe, 2 jo-blocks (2 x 1"?). One against the anvil of a very good (as in accurate) micrometer and the other against the micrometer spindle? When you take a part out of the machine measure again and see if you still get the same result. If yes then maybe good to go?

This was my thought. The other option, like Buck said would be a go no/go gage.

RJT · Jul 21, 2020

I would really like to measure to know where I am within the tolerance rather than a go no go. The jo block option is a possibility I'll try. May be a bit clumsy and require 2 sets of hands.

jariou · Jul 21, 2020

A temporary go-no go gauge could be made up with gauge blocks and an accessory kit like this Mitutoyo Square Gage Block Accessories (Inch) - Series 516 - 516-612 - Penn Tool Co., Inc.

This one is for square blocks, so perhaps not ideal for the situation here. But those kits are quite useful. I got one here, made by Vis I think, for $150 maybe a year ago. I find so many uses for those for tricky measurements.

Jacques

Machinist_max · Jul 21, 2020

MITUTOYO SERIES 343 CALIPER TYPE MICROMETER.
Caliper Type Micrometers - Series 343,143

Gordon B. Clarke · Jul 21, 2020

RJT said:
I would really like to measure to know where I am within the tolerance rather than a go no go. The jo block option is a possibility I'll try. May be a bit clumsy and require 2 sets of hands.

I was going to add to my post that 2 sets of hands would make things easier but you might just be very dexterous

As an afterthought I'm wondering why the tolerance is only 0.0002"? I'm also wondering if the original dimensions were metric and someone played safe (and expensive) transforming to inches. Both diameters are "weird" inch dimensions.

OD 58mm +0 -? and small diameter 15mm +0 -? seems more logical.

Gordon B. Clarke · Jul 21, 2020

Machinist_max said:
MITUTOYO SERIES 343 CALIPER TYPE MICROMETER.
Caliper Type Micrometers - Series 343,143

That would work except it isn't accurate enough for a 0.0002" tolerance.

The accuracy given in the link is ±.00025in.

Milland · Jul 21, 2020

Gordon B. Clarke said:
That would work except it isn't accurate enough for a 0.0002" tolerance.

The accuracy given in the link is ±.00025in.

Yeah, you can't count on a cantilever design like that to work to the accuracy needed. The only way it could possibly work is to constantly check it against reference gage blocks and confirm repeatable discrete readings within no less than .0001", and even there you'd be fighting changes in parallelism of the faces.

eKretz · Jul 21, 2020

I've used these before for similar stuff:

https://www.starrett.com/metrology/product-detail/224AARLZ

Not sure if they have a tenths reading version though.

Tony Quiring · Jul 21, 2020

Calipers...

Most have the inside ano outside jaws yes?

Good quality calipers held on part using outside jaws with a Mic measuring the inside jaws.

The caliper telegraphs the measurement.

The caliper needs to be checked to insure it works this way, simple test on similar sized stock that the Mic can be used on.

Sent from my SAMSUNG-SM-G930A using Tapatalk

sfriedberg · Jul 21, 2020

Shallow bore gage? Most of them read ODs just as well as IDs, can be trivially set from a gage block stack, and have a dial indicator of whatever precision you want to pay for.

Measure a stubby diameter next to a large face

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