ID micrometer, is it worth buying one?

[taydin]

I am currently making seats for 8 bearings, like the ones below. Made the first one, but really struggled with measuring using my caliper. I needed to spend several minutes seating the caliper properly, getting the right feeling about the caliper position and reading the dimension. This first one ended up being a nice tight fit.

So my question is, will buying an ID micrometer make things easier? Based on how those look, it seems I will still need to spend several minutes positioning the mic to the hole, getting that right feeling and making the measurement.

[bob308]

dial bore gage is the way to go.

[firbikrhd1]

If you do a lot of this kind of work it probably would pay to get a dedicated bore gauge or inside micrometer of some type. I've found that I can obtain very accurate results by using telescoping gauges and an outside micrometer. As a machinist you probably already have an outside mic and telescoping gauges as a set are not terribly expensive but cover a wide range of diameters.
I am not all that familiar with dial bore gauges such as bob308 mentioned, but I assume you need a standard or set of standards something like ring gauges to use them. If that is the case the cost may add up to more than you see fit to spend. An outside micrometer may work as a substitute for ring gauges, but I repeat, I am not very familiar with the use of dial bore gauges.

[taydin]

As far I have seen, dial bore gages cover very little range. For example, looking at the Asimeto listings:

6 - 10mm, 10 - 18mm, 18 - 35mm, 35 - 50mm and so on. Not sure what these cost, but it will quickly add up it seems.

I have seen telescoping gages in one of Keith Fenner's excellent videos, but no matter where I asked, nobody has them here in Turkey. I do have a micrometer set covering the 0 - 100mm range, so a telescoping gage would be perfect.

[Mcgyver]

dial bore gage is the way to go.

+1. Good ones are expensive and cover limited ranges....however there's no free lunch. Proper fits of roller element bearings are one the most demanding jobs and internal bores are very difficult to measure to tenths without a good dial bore gauge.

Next best would be carefully making and measuring go/no go gauges. Basically it transfers the problem to the OD so you can use a tenths (or .001mm) mic.

so a telescoping gage would be perfect.

imo they just don't deliver adequate accuracy for perfect and reliable fits with roller element bearings. You can do it, but things come together with roller element bearings like they're supposed to when you can reliable hit a tenth or two and that is a very tall order for telescoping gauges

but I assume you need a standard or set of standards something like ring gauges to

you can do just as good a job with a micrometer or gauge block stack, just not as quick and convenient as with a ring. I've got a number of digital boramatics and other three legged contraptions and they need rings for sure...I often find the bore gauge and mic more convenient. might change if I ever get all the rings I need, but with a bit of practice its not difficult using a bore gauge with a mic. You can set the mic to a gauge block if necessary

[becksmachine]

Ok, I am assuming here that when you say "caliper", you are referring to a dial/vernier/digital style.

You are finding on your own some of the disadvantages of using this style instrument for relatively precision measurements, difficult to hold properly (square to the bore, consistent contact pressure etc.) and then difficult to see/read when this is all achieved.

This also completely ignores the intrinsic limitations of the instrument itself, that it is only capable of accuracies of + - .0005" or + - .001". Add to this the difficulty with proper positioning, you are doing well to maintain overall accuracies of + - .001"-.002".

You didn't say what amounts of press fit you are trying to achieve here. If I had to guess, that size bearing could use anywhere from .0005"-.002" interference. These look like wheels for your crane system? If so, you are making 4-8 wheels with 2 bearings per wheel? If so, I will go out on a limb here and say that you will be doing very well to achieve a 50% success rate, measuring with a digital/dial caliper.

The theme here is bore micrometers where invented for a reason, those reasons are as valid now as 50 or 100 years ago. Whether it is an ID style micrometer or dial bore gage or the three legged Intrimik/Holetest style, you will achieve much more consistent results. This can also be achieved with telescoping gages and a micrometer, but these require much more experience/practice to achieve consistent results.

Dave

Flame suit on!!

[RLWP]

Could you turn up a simple go-no go gauge? Something with a spigot perhaps a couple of thou under, then another spigot at size. Once the undersize spigot goes in, you know you have less than .002 to go

You can make this using an external micrometer

Richard

[taydin]

Correct me if I am wrong, but the dial bore gauge seems to be a much more sophisticated telescoping gauge. It has three contact points, which takes care of centering it in one plane. Then there is the dial, which allows you to find the max spot easily...

[taydin]

Ok, I am assuming here that when you say "caliper", you are referring to a dial/vernier/digital style.

You are finding on your own some of the disadvantages of using this style instrument for relatively precision measurements, difficult to hold properly (square to the bore, consistent contact pressure etc.) and then difficult to see/read when this is all achieved.

It is a non digital, no dial 150mm Mitutoyo caliper.

You didn't say what amounts of press fit you are trying to achieve here. If I had to guess, that size bearing could use anywhere from .0005"-.002" interference. These look like wheels for your crane system? If so, you are making 4-8 wheels with 2 bearings per wheel? If so, I will go out on a limb here and say that you will be doing very well to achieve a 50% success rate, measuring with a digital/dial caliper.

Well, the press fit that I achieved for this particular case is that I was able to hammer it in with a mallet without much fuss. These are part of the wheels for my scissor platform. I will start a thread for that soon, just don't have enough work into it yet to justify a new thread. Here is how I did this:

The bearing is 52mm OD. I worked on the hole until I came to within 0.2mm. Then I let it cool off. Then I took off the remaining 0.2mm. The bearing didn't fit. I retracted the cutter and went in again without changing the cross dial. This shaved off some more. Bearing still didn't fit. I advanced a quarter division on the cross dial (0.0125mm theoretically) and then I hammered it in.

This is part of the wheels for the scissor platform. In the picture below, the top part and the bottom part with the long shaft in between:

[taydin]

Could you turn up a simple go-no go gauge? Something with a spigot perhaps a couple of thou under, then another spigot at size. Once the undersize spigot goes in, you know you have less than .002 to go

You can make this using an external micrometer

Richard

I already have the bearing sleeve itself. I didn't really understand how such a gauge would help in this case?

[JCHannum]

For a few pieces, the expense of buying an inside micrometer set might not be justified. Things to consider are that most sets start at 2" or 50mm and go up. There are some that start at 1-1/2" or 40mm. In a shallow bore such as yours, the micrometer head might be too large to permit an accurate reading.

Inside micrometers are typically graduated 0.001" and 0.01mm which might not provide the accuracy needed. Further, they do require calibration with a standard or micrometer for best accuracy.

The suggestion of a plug gage for a few bores is probably the best so far. While you do have the bearing, using a plug gage will let you know when you are close to the bore.

Since this does not appear to be a highly stressed application, don't overlook anaerobic adhesives. Loctite and others manufacture bearing retaining adhesives that eliminate the need for a dead nuts press fit.

[RLWP]

I already have the bearing sleeve itself. I didn't really understand how such a gauge would help in this case?

When the bearing sleeve will drop in, it is too late. Turn up a plug that is slightly smaller and go on boring until that falls in and the bearing sleeve doesn't

Richard

[jimsehr]

I just looked at ebay and inside mics are going for cheap. You can always get a reading and then check the reading with outside mics. So I would buy one in a second. I think they are a real time saver.
jimsehr

[KiddZimaHater]

A quality set of Inside mics is the way to go.
Get a 0-6" set of either STARRETT or MITUTOYO.
Once you get the "feel" for them, they are dead-nuts accurate.
_

[oldtiffie]

You should be able to hold +/- 0.0005" or better with:

- spring or friction internal calipers and telescopic bore gauges:

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/idmeasdevice1.jpg

- digital internal bore gauge:

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Digital_caliper1.jpg

- internal micrometer:

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Insidemic50to300_1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Insidemic25to50_1.jpg

- or make a "stick" gauge (using a normal external micrometer) - the principle on which it operates is the basis for all of the above:

http://i200.photobucket.com/albums/aa294/oldtiffie/Sketches/Stickgauge1-Rev1.jpg

All of these require a very good "feel" to accurately transfer and measure a distance (includes diameters) - and is a "manual" skill which may take some time and learning to be accurate and consistent.

If it were me I'd opt for the spring or friction caliper and the outside micrometer (option 1) or make a "stick" and use that (option 2).