Help me remember dial bore gauge basics

GregSY · Jul 28, 2020

30 years ago, I worked in a shop and used these gauges all the time...but I've forgotten some details.

As I recall, you would used a setting gage of a given diameter to first establish the baseline of the dial gauge. Then, you'd use the gauge to measure the bore, etc.

Is that right? In other words, without the setting gage, the dial bore gauge is not that useful?

What range is considered acceptable when selecting a setting gage? In other words, if I want to measure a 2.100" bore, is there any issue with using a 2.090" gage as the starting point?

I'm looking at buying this gauge but also want to know if I need to buy setting gages etc.

https://www.amazon.com/Mitutoyo-511...ds=511-753&qid=1595971320&s=industrial&sr=1-2

eKretz · Jul 28, 2020

Using a standard ring type of gage is the quickest and easiest way to set them, but they can be set with a micrometer or gage blocks also. It's just a lot more fiddly and more of a pain in the butt - you have to spend some time making sure you have found the low point repeatably.

Sunnen I think made a setting fixture with a mic head on board for quickly setting different sizes. I have bore gages from 1/16" or so up to 12"+ and I usually use a micrometer for setting unless I have something that is super tight on tolerance. Then gage blocks or add the cost of a ring gage to the job.

As far as size range goes, my Starretts are settable in a sort of infinite range by sliding the housing containing the dial indicator up and down the extension shaft then clamping it, so I just set the gage at the desired size in the center of the indicator travel where it's at zero right in the middle. Not sure if the Mitutoyo is the same.

gappmast · Jul 28, 2020

Only use a ring gauge to set a dial bore gauge if the ring gauge is the size you want to measure. Using a wrong size ring gauge and then using a offset for you part size is not an accurate way to set a dial bore gauge. If you don't have the correct ring gauge your best method is a micrometer. Dial bore gauges are a comarator and if you use them as a comparator they are a fine tool.

eKretz · Jul 28, 2020

gappmast said:
Only use a ring gauge to set a dial bore gauge if the ring gauge is the size you want to measure. If you use a ring gauge that is of a different size and try to offset your size is likely to be off. Dial bore gauge indicators are only accurate to one graduation per revolution at best so tolerances can stack up against you. If you don't have the correct ring gauge use a micrometer. Dial bore gauges are a comarator and if you use them as a comparator they are a fine tool.

Yes, absolutely. Target size should always be your zero. Comparator type gages should always be used that way.

GregSY · Jul 28, 2020

So help me understand how you would use it to measure an ID...let's say a bearing bore of 2.100".... and compare it to then the shaft journal OD...let's say 2.097".

How would you use a micrometer to establish the setting of the dial bore gauge? I'm starting to recall that these gauges use a fixed pin and an opposing pin that actuates the dial indicator...so maybe that is how?

Which brings me to my next question...the gauges I used to use had a three-lobe design, spaced 120 degrees apart, and could measure deep down a cylinder. Is that a different type than the Mitutoyo I showed?

eKretz · Jul 28, 2020

Yes, in that type of bore gage the measuring contacts are diametrically opposed, one is fixed and the other actuates the dial indicator. The other spring loaded contact points are only to centralize the gage in a bore. There are other types made, some do use three points.

I normally rest the dial bore gage in the position I will use it, (almost always horizontal on a bench) then hold the micrometer as though I'm measuring a part with the mic set to the reference size. Manipulation of the mic follows until I'm sure I have the low point repeatably indicated on the dial, then I roughly set the indicator housing to get it close and check again. Next I note how far off it is from the zero and shift the indicator slightly to bring it in the final amount. Final check to make sure everything is good and if necessary rotate the bezel a slight amount for last tenth or two adjustment.

bryan_machine · Jul 28, 2020

Pete Stanton's youtube channel has a video of it. It's no different from what is said above except that he focuses on using gage blocks with a gage block holder kit. (Those gage block holder sets can cost more than the gage blocks, but in my experience are worth it.)
Setup A Dial Bore Gauge And Bore - YouTube

In my shop a special rule applies - any project requiring a bore gage will manifest this after about 9pm, and never require a setting ring already at hand.

3 lobe bore gages presumably require setting rings.

At least the mitutoyos I have cover ranges speced for the gage - as in "from 0.x" to 0.y" sort of thing. Typically can be set for any value in that range you want.

gappmast · Jul 28, 2020

GregSY said:
So help me understand how you would use it to measure an ID...let's say a bearing bore of 2.100".... and compare it to then the shaft journal OD...let's say 2.097".

How would you use a micrometer to establish the setting of the dial bore gauge? I'm starting to recall that these gauges use a fixed pin and an opposing pin that actuates the dial indicator...so maybe that is how?

Which brings me to my next question...the gauges I used to use had a three-lobe design, spaced 120 degrees apart, and could measure deep down a cylinder. Is that a different type than the Mitutoyo I showed?

In your case I would set the dial bore gauge with your micrometer so zero on the bore gauge is the shaft size, 2.097". Now when you measure the bearing bore with the bore gauge you will be showing .003" on the pluse side of zero, which will be your clearance.

For you second question the gauge you have will be able to measure down a cylinder as deep as the shaft on the gauge is long.

Robert R · Jul 28, 2020

GregSY said:
I'm looking at buying this gauge but also want to know if I need to buy setting gages etc.

https://www.amazon.com/Mitutoyo-511...ds=511-753&qid=1595971320&s=industrial&sr=1-2 View attachment 295179

There is a accessory, part number 515-121, for the Mitutoyo height master that is designed for easy setting of a bore gauge It consists of a spacer block that clamps to the base of the height master and rests on the granite plate and a extension block that clamps to one of the moving gauge blocks. The bore gauge probe and fixed anvil are placed between the extension and spacer blocks for setting.

The height masters appear on E-Bay in the $300 range. The accessory kit is in the $75 range. These were very expensive items at one time. The demand is no longer there. They are a much less expensive alternative to a set of setting rings.

There are several versions of the accessory block available to match the different versions of the height master. You will need to check the online catalog/user manual for the height master to get the correct block.

RJT · Jul 29, 2020

I've used gage blocks , micrometers and rings in the past. Several years ago we invested in Sunnen system (setting fixtures and gages) and I would never go back. Setting system is quick and accurate, you will use the bore gages much more often because it's much more convenient. But like any good tooling, its expensive in the short term, but you forget about how expensive it is after several years of use with no problems.

Mike1974 · Jul 29, 2020

These are great for the price and the range

https://www.mscdirect.com/product/details/92828045

Use some known/calibrated gage blocks and you are good to go. Works similar to using a mic or gage blocks, you have to fuss with them a bit to get the low point as kretz said. But I found with a little practice it wasn't much more trouble than using a ring gage. My personal opinion these are fine down to a few tenths, once you have confidence in yourself setting the bore gage correctly by sweeping to and fro and side to side.

GregSY · Jul 31, 2020

Thanks all.

My gauge arrived yesterday but I haven't had time to play with it yet.

What I do wonder is...no matter how I 'zero' the gauge, it seems the ambient temp and (maybe) humidity would also play a role when tenths are at stake. My shop is not outdoors but it also isn't a finely controlled environment.

gappmast · Jul 31, 2020

Temperature will play a role on the gauge and the parts your measuring. Ideally you should let you measuring equipment and parts soak at 68-70 degrees for 24 hours before measuring.

GregSY · Jul 31, 2020

I looked at the Mitutoyo 515-311 on Ebay, they are $1000 at the least.

There is a 515-310 that can be bought for around $300. It is the 'non-staggered' version.

But I gotta admit, both look like lunar space modules and their function is not apparent to me!

EmGo · Jul 31, 2020

RJT said:
I've used gage blocks , micrometers and rings in the past. Several years ago we invested in Sunnen system (setting fixtures and gages) and I would never go back.

The setting gauge is great, also the Sunnen bore gauges use a lever arm instead of a telescoping piston, so they wear less and are more accurate in use.

This is one product from Sunnen that really is better.

Mike1974 · Jul 31, 2020

GregSY said:
I looked at the Mitutoyo 515-311 on Ebay, they are $1000 at the least.

There is a 515-310 that can be bought for around $300. It is the 'non-staggered' version.

But I gotta admit, both look like lunar space modules and their function is not apparent to me!

Also known as a cadillac gage. You set the bottom step on a .400 gage block IIRC, then zero out the dial, then crank up to whatever reading you want, then use an indicator to compare the step to your part. They are stepped in such a way that you can measure either on top or bottom, so you could check say from one surface to the underside of a flange or similar.

edit: Yes, temp and humidity will affect your measurements. If your gage and part are the same temp you should be able to mathematically figure the "true" size at 68-70deg.

Robert R · Jul 31, 2020

GregSY said:
I looked at the Mitutoyo 515-311 on Ebay, they are $1000 at the least.

There is a 515-310 that can be bought for around $300. It is the 'non-staggered' version.

But I gotta admit, both look like lunar space modules and their function is not apparent to me!

Shopping on E-bay does take some patience. My 515-311 was purchased for $300 including shipping. Take a look at the online instruction manual to see how the height master is used and how it is set up to zero the bore gauge.

eKretz · Jul 31, 2020

The temperature change issue is one reason it's nice to have a quick and easy way to reference your gage. If you're holding low tenths tolerance you should be doing that frequently anyway. And yeah, the Sunnen setup is pretty darn good.

Matt_Maguire · Jul 31, 2020

GregSY said:
So help me understand how you would use it to measure an ID...let's say a bearing bore of 2.100".... and compare it to then the shaft journal OD...let's say 2.097".

How would you use a micrometer to establish the setting of the dial bore gauge? I'm starting to recall that these gauges use a fixed pin and an opposing pin that actuates the dial indicator...so maybe that is how?

Which brings me to my next question...the gauges I used to use had a three-lobe design, spaced 120 degrees apart, and could measure deep down a cylinder. Is that a different type than the Mitutoyo I showed?

In your example I'd set the bore gage to "0" with the mean of your numbers directly set on the micrometer & locked (even the old tenths on the barrel kind).

I use a bore gage as a comparator not an absolute measure. If you don’t have the nominal (desired bore) size ring gage, interpreting the exact size by add/subtracting with the dial face can lead to trouble.

If your using jo-blocks, mics or height masters I set “0” to the desired value which is usually somewhere between your min/max dimension.

Good luck,
Matt

Help me remember dial bore gauge basics

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