Thread: Bore gauges

Depends on the quality of the bore gauges.
Telescopic gauges are pretty close.
A lot of it will depend on the operators feel.
On bores in excess of 3"/75mm I use inside mics.
Bore gauges in a sense are better suited to deep bores.

Dear Mike I have used bore mikes in industry and only have confidence in them in the smaller sizes ie if you can get your hand in the bore use an internal mike. My bore mike goes from 1 1/2 inch to about 6 inches in one set. I have always disliked the telescopic type because they can move when removing from a bore. So it is a problem when working in the smaller diameters. yours 4-6-4

Right

I was looking at this but the postage is rather too high ..I don't know why so many US ebay sellers want to rip you off with postage

DIAL BORE GAUGE SET A831 | eBay

I have a set of these, ranging from 18 .. 150 mm (iirc).
A bit of work to set them up. Good for deep bores, good repeatability.

Together with a dial indicator (digital) that can be preset, you get an actual reading and don't have to make confusing math (read: I got confused sometimes).


Nick

That bore gauge set has a few space's with nothing in them ?

It also doesn't look like it has a lock.

And........ it has a two sided anvil that rests against the bore, wouldn't the accuracy change with the diameter of the bore ?

And how would you check it with your micrometer ?

If it does work it is cheap though.

Hi

I ended up buying one of these

NEW BROWN & SHARPE INSIDE MICROMETER # 599-263-1 MADE IN ENGLAND | eBay

I think its a good deal as the postage is very cheap . I will have to wait and see if it's a genuine B&S or a Chinese copy

Did you consider buying something that had a larger range of sizes.
Wouldnt really worry much about the quality as you would normally check the mics reading against an outside mic or vernier.
Looking at the one pictured it only appears to maybe be a 2"'/50mm mic,probably better off with the telescopic gauages.

Originally Posted by pipeclay

Did you consider buying something that had a larger range of sizes.
Wouldnt really worry much about the quality as you would normally check the mics reading against an outside mic or vernier.
Looking at the one pictured it only appears to maybe be a 2"'/50mm mic,probably better off with the telescopic gauages.

I did some research and apparently it is 1" to 2" in its original box but it can be used up to 12" , with the extension rods .. I might have to make up some rods for it . I will wait and see when it arrives ..MIKE

Originally Posted by morrisman

..I don't know why so many US ebay sellers want to rip you off with postage

He's probably not making anything on the postage. Check this out:

International Price Calculator

Postage from the US can be extortionate. I've found that postage from the UK is MUCH cheaper.

Inside micrometers aren't for measuring. You just can adjust them to some size and see wether it fits (bore is bigger) or not (bore is smaller).
Well, you could adjust them in 1/100 increments and try to get a fit. But still, there is not defined force at the measurement pins. If you rock the micrometer to be perpendicular to the bore, you have an almost infinite lever. Just a tad adjusted over the actual bore will result in a huge force.

One principle of measurement is to have a defined force. See ratchet on a micrometer, spring in a DI, etc.
Inside micrometers don't follow that principle!


Nick

Did you buy that because of the name or just impulse.
There are numerous other brands of inside mic available on ebay now and other times that allready come with different length legs.
Others are a tubel type,heavier construction.
With the other sets that come with the extensions you wouldnt have the trouble of making your own up.
Most times the older sets can be had for under $100.
Good luck with your purchase,it just seems a waste unless you only need that size range.

Greetings Chaps I am afraid that the comments by Mueller are some what surprising. I have always checked an inside mike with an outside mike and it requires a certain amount of feel. But I have never trusted an inside mike be it the ordinary type or the stick type to give an accurate reading of a bore on the inside mike alone. The bore mike I have has a dial and you set it with an outside mike. Its a bit fiddly but it works especially on the deep bores. I will take pics tomorrow. After working on hydrolic cylinders up to 1/2 meter in diameter I found that if you could get your hand in the bore stick mikes were best. For the smaller sizes the dial bore mike was best. That is 1 1/2 inch bore up to about 4 inches. Yours 4-6-4

Originally Posted by MuellerNick

Inside micrometers aren't for measuring. You just can adjust them to some size and see wether it fits (bore is bigger) or not (bore is smaller).
Well, you could adjust them in 1/100 increments and try to get a fit. But still, there is not defined force at the measurement pins. If you rock the micrometer to be perpendicular to the bore, you have an almost infinite lever. Just a tad adjusted over the actual bore will result in a huge force.

One principle of measurement is to have a defined force. See ratchet on a micrometer, spring in a DI, etc.
Inside micrometers don't follow that principle!


Nick

Nick , I think that is a esoteric point of view.

In practice , once you get the ' feel ' of a particular instrument , you will get to know its idiosyncrasies and you can get accurate results . After I have bored out a hole , I would like to know if it is tapered or not , this inside mic should be OK for that .

PC .. I never seem to find those 100 dollar inside mic sets on ebay

Mike

Nick , I think that is a esoteric point of view.

No, it is not.
If you look at the contact pin:bore, you do have a wedge. The closer you get with the adjusted diameter to the actual diameter, the more acute the wedge gets. And the greater the ratio (that amplifies the force). You almost get an infinite amplification. Its similar to a knee-lever (hope that's the word in English) that also has infinite big ration (but also infinite small move) at the point were both legs are in line.

In practice , once you get the ' feel ' of a particular instrument

Metrology doesn't define a "get the feel" of an instrument. But it defines repeatability independent of the operator.


Nick