Setting Bore Gages

[The real Leigh]

Often when people feel measurements like that they're feeling what they want to feel and getting "sympathy" measurements.

That's a very common problem.

I never look at the reading until I've finished adjusting the instrument.

- Leigh

 

[Gosser]

Regarding (indicating) split ball bore gages/gauges.
I experimented with setting these (in this case ~12mm) against a digital mitutoyo digital 0-25 micrometer. Checking against a setting ring I get within around 3-5 μ. I suspect this is typical due to the fact the gauge is able to skew in combination with other factors. Temperature was not controlled.

But how close do you get? Is my technique bad?

I know it's recommended to set against a setting ring.

I have done the same thing many times. The only difference is that I measure in the imperial system. I normally find .0002"-.0003" difference between a ring gauge setting to a micrometer setting. This is about 5-8 microns to our European counterparts. I always find that after setting the bore gauge at "0" to the ring gauge that the bore gauge will read minus compared to the same micrometer reading.


Another factor that may well come into play is whether or not the thimble clamp has been clamped on the micrometer....If it has the accuracy of the screw thread of the micrometer may well come into play.

Having said all of this it is important to remember that gauging of any manner is a "comparitive measurement".....it is a comparison of one form of measurement to another...You can use various methods but the only thing that matters is that you get a consistent result .

As far as temperature control goes I would think that the gauge(s) would acclimatise at a similar rate to the workpiece(s) in a QC environment.


Gosser

 

[cypherp]

I'm aware of "sympathy" measurements, no doubt they may influence my results.

I always find that after setting the bore gauge at "0" to the ring gauge that the bore gauge will read minus compared to the same micrometer reading.

I re-zeroed the micrometer without letting the friction clutch click and got closer to zero compared to setting rings. A couple of clicks makes the micrometer read -0.003 to -0.004 mm. So supposedly measuring force related.

I did check the micrometer against gauge blocks before commencing.

Here are some operating instructions for the diatest type gages.
http://www.diatest.com/fileadmin/do...auge/Split-Ball_Operating_Instructions_EN.PDF

It says:

Additional setting means for split-ball probes:
Slip gauges, snap gauges: Well suited for
zero-setting in stationary gauging. Micrometer
for secondary measuring jobs.

 

[TDegenhart]

OT - Starrett high precision micrometer

As long as the topic is approaching how to measure in units of Planks, I recall 30 or 40 years ago Starrett made a very high precision micrometer that required setting the measurement force. I don't recall much about it other than that. I have not seen any reference to such a micrometer either. Does this ring a bell with someone?
Tom

 

[PeteM]

As long as the topic is approaching how to measure in units of Planks, I recall 30 or 40 years ago Starrett made a very high precision micrometer that required setting the measurement force. I don't recall much about it other than that. I have not seen any reference to such a micrometer either. Does this ring a bell with someone?
Tom

Starrett, like just about every micrometer maker, has had a bunch of attempts at controlling anvil pressure -- the simplest of which are a ratchet or friction thimble mechanism. Starrett made a high precision micrometer, which has a sort of spring loadable spindle. Looked pretty much like a standard mic. It was a bit awkward to use and fragile in rough handling; but it did work. Starrett also had bench mics with comparators at the anvil end; adjustable for pressure.

 

[Glenn Wegman]

Van Keuren's Light Wave Micrometer functioned on consistant anvil pressure.

Not a new concept...

As mentioned in my earlier post, I have found no disparity in readings between a ring gauge and a micrometer when setting Sunnen split ball type .0001" bore gauges, but I lock the micrometer anvil while it it clamped to a corresponding gauge block stack, then remove the blocks.

A split ball type gauge will, however, be happy to read in error of the film thickness of the honing oil if the bore is not flushed and dried prior to use.

 

[TDegenhart]

I would be interested to see (pictures of course) what you are doing.
Tom

 

[oceanpout]

I use the old starrett height gage with 1" gage block myself have not had any rejects! But only worked to like +-.0002" . I would like to check one of these out
53-646-000 BORE GAGE SETTING MASTER KIT FOWLER at east tec in may

 

[Higher Precision]

Bore Gage Calibration

Hi Everyone,

A few months ago, I wrote a blog about bore gage calibration and the different methods people use to set their bore gage. This may be informative to some of you. Please click on the link below to see the blog post about setting a bore gage.

Bore Gage Calibration

 

[CBlair]

Welcome, thanks for joining in, hope the business goes well for you.

Charles

 

[TheKen]

We use a Gagemaker Mic-Trac to calibrate our hand tools (calipers, OD-ID-depth micrometers, bore gages, etc). Although we don't use it for setting bore gages, that is it's original purpose. It will set a wide range of bore gages and it is very accurate (.0002" / 24").

If you are going to have to purchase a large number of ring gages, then maybe take a look at the mic-trac. Depending on the number of ring gage you might need, the cost may be comparable. Not sure how well it would hold up in a shop environment as we keep ours in our lab. But that would be something you could ask about.

I've included a link of a picture of a Mic-Trac.

http://dl.dropbox.com/u/1125024/mic-trac.jpg

Hopefully this will give you a few more options to think about.

Ken

 

[Higher Precision]

calibrating 3-point bore gage

A few years ago I remember seeing an interesting product by Bowers Metrology out of England. They made a fixture they use to sell that also incorporated a high accuracy Sylvac probe and readout. It was a little pricing but also cheaper than buying a lot of rings as well. I just did some quick searching and only found a picture of it on a website of a company in Australia. I'll try to get some better information for you.

ASTEG - Bore Gauge Calibrator