Fowler Bore gauge

I have a similar bore gage...Fowler, but not the extended nor is it digital...many of the same issues, however...couldn't beat the price with a really big stick, tho and it is accurate, which is what really matters.

As to the setting gages, I suppose that if you have a job or three that you are continually setting up for, I'd get ring gages for those sizes, otherwise, I've always used just a standard outside micrometer. It's always been accurate enough for any job I've ever done.

Mike

I'd agree pretty much with Mike regards setting any dial bore. If you are working to reasonable tolerance, half thou or more, you can set the gage with fair precision with a calibrated micrometer, but if you're working close, couple tenths or less, even with gage blocks it's hard to hit the setting dead nuts. I've set many a gage that way, then followed up with a ring, only to find I'm off a tenth or two. If you do work for anyone outside your own shop, and size matters, I'd suggest rings.

Harold

"oldjag" wrote in news: snipped-for-privacy@h54g2000cwb.googlegroups.com:

You set it with a gage block setting tool.

-- Anthony

You can't 'idiot proof' anything....every time you try, they just make better idiots.

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Is that a bit like this one:

I assume this means the bore gauge must be checked against a standard with each different extention bar tip, ie before every measurement of a different size range. I'll have to find a setting tool and some gauge blocks.

More to the point is that it has to be set for EACH hole size. As far as I know, there are no bore gages that let you swap out the anvils and be at the last size of that anvil.

Mike

Several folks have mentioned ways to set a bore gage. In the automotive world we use a setting fixture that uses a 'tenths' mike built into a fixture. See the following Sunnen site, the 2 upper items are setting gages with a bore gage being set.

You can't see small , even , changes on a digital gage . I have many ENCO and some i made some extensions on ...

But if you can get your DTI in the hole , its FAR more accurate and easier to read !

------ Cut the end off an expensive $110 Mitutoyo 0-1" Mike and use it as : setting rings / ht gage / and anything a mike wont fit in . I have 42 ENCO 1-2-3 blocks . Ill cal them , cal the mike , use mike as HT gage and read the bore gage to 50 millionths and then zero the bore gage .... I know , I know , there are store bought stuf for this .... But its cute to see the .00005 readings !! Impressive ..

w/ DTI ya get a very small range of accuracy . If i needed repeatability and better reading , id use DTI , if it were not needed , then a std bore gage analog indicator is OK . Ya gotta move it 4 ways !! Check it by up/down many times as ya force it R , then repeat with force to the left , see if the friction is forcing it to stay off center ..

DTI is 7 grams pressure ....less problems here .

oldjag wrote:

Sir, you did not state which model you have. If it is one with THREE contacts (anvils) , it will require a ring-gage to accurately calibrate it.

If, however, it is one with an fixed anvil directly opposed to the moving gage-point, as I suspect yours is, from reading your original post, then it can be accurately and reliably set with only a micrometer.

These can be quite accurate and reliable with proper setting and careful reading..

Flash

Have you had the pleasure of having such a setting verified by a second source? Even using gage blocks, it's not uncommon to miss the setting. We're not talking about a huge amount here, usually only a tenth or two, but that was often the tolerance at hand.

I agree, you can be accurately set by the method you suggest, but not reliably. All to often, when I was running precision grinders, we used to set our dial bore gages with gage blocks, only to have the inspection department reject parts. They had the luxury of rings of needed sizes. We finally resorted to having inspection do the setting. It's just too hard to hit dead center by other methods.

Maybe the entire grinding department was staffed by a bunch of morons. Don't think so, though. They (we) were more or less the "cream of the crop" from a shop of over 100 employees. Very few were selected for the grinding department, and those that did the grinding didn't rotate to other departments.

Harold

And do those use a setting standard to ensure that a specific measurement is arrived at, or do they just reference the relative movement of the hone?

Cheers Trevor Jones

Harold, I worked as Tool & Gage/Calibration Supv (with a lot of tother junk thrown in because no one else was goofy enough to accept it all) for thirteen years at large multi-naitonal company's home plant, here. (So much for credentials whatever they are worth).

You are right, in reference to grinding - it needs to be good. All bore gages there were 3-pt, set to calibrated ring-gages. +/- .0001"

For boring, and the other =/- .0005" and up stuff, we set all the dial bore gages on calibrated and certified mics. Where ID was under 5" and tol was +/- from .0002-.0005, we used a setting gage with a large (4" O.D. ) scale - just a glorified mic, actually, but GOOD.

Each setting was "verified" by one of the other tool-crib attendants before issue of instrument.

On several CNC cells where certain parts were made nearly full-time, we had Federal Air-gages. Just about couldn't argue with them ever.

Still, if you want it right without going the air-gage route, it requires a three-point gage and set by ring.

Of course, there IS a plug-gage. Is that possible/economical for your set-up? Only if you are doing many of the same thing, probably?

Flash

I agree on all points, including the Federal air gages. Just wanted to emphasize that setting by micrometer or gage blocks has its drawbacks and should not be considered the last word under certain circumstances.

We used one of the Federal air gages for a specific product, the bearing housings for the stable platform of the missile. We ground them by the hundreds. The Federal air gages can discern miniscule differences easily. I'd often find a bore out of tolerance by a few millionths, and inspection didn't buy them unless they were within limits +.0002"/-.0000"), @ 1.6250". It was interesting to learn to take out .000020" and do it routinely and reliably. . Remember, this was back before CNC-----it was all done manually---on an old Heald 271 internal.

Harold

The setting fixture is checked against the appropriate mike standard for the inch part of the measurement, then the setting mike is turned out to set the .0000 portion. The bore gage is used frequently to check honing progress. And good practice says to check against the setting fixture occasionally during the honing job.

Alex

The setting fixture is checked against the appropriate mike standard for the inch part of the measurement, then the setting mike is turned out to set the .0000 portion. The bore gage is used frequently to check honing progress. And good practice says to check against the setting fixture occasionally during the honing job.

Alex