Bore Gauge

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guys, even the you tube videos are not right ---in a way !
look at 2:40 (Almega)
and 7:40 ( SHopshoe)
Look CAREFULLY at the video
in each case they pull the telescopic gauge and are NOT perpendicular to the bore !
This is Important .. even ABom said he was off a bit.
For some reason ( I have never heard this method in shops for 60 years) they talk about dropping and catching the gauge.. I don't care if that is their method, but when you pull the gauge . YOU must be in the plane that is through the center.. look at the videos easy to see the error!

Rich
 
Hi Guys,
I have various ball bore gauges but this is not my preferred method !
15-09-2018-001.JPG

This is the method that I was taught using dividers and then measuring them with a micrometer. I've used this method for years without a problem. Its also easy to detect an out of round or tapered bore. It does depend on feel though.
 
Hi Guys,
I have various ball bore gauges but this is not my preferred method !
View attachment 151876
This is the method that I was taught using dividers and then measuring them with a micrometer. I've used this method for years without a problem. Its also easy to detect an out of round or tapered bore. It does depend on feel though.
I used that type too.
Very hard to use for press fits.

In low in machine shops the use that for OD work and use a ID mic it works but a real pain to get a good job

Dave
 
Hi Dave, Guys,

For press fits and bearing housings, I find that temperature is the big gotcha !

Its important to let the work cool down before measuring, particularly with bearing/ball race fits. The Chinese and Japanese manufactures tend to super glue bearings in place, rather than press fit.
 
I, like Baron post #22, use caliper mostly. I calibrate myself (feel) beforehand on an old bearing of a similar size. To confirm, I'll set the caliper at a thou or 2 undersize with the mic. Then check the bore... Then same at size and a thou oversize. Somehow helps me..
I have a dial gauge I bought. But haven't used it much. But I grew up using one doing honing on re-bores on engine blocks as a teenager... had to be within 0.001in. parallel. Or whatever the manufacturer had specified. And same for size. Coarse stones to get from bored size to a thou under finish I.D., then fine stones to hone the finished size and diagonal pattern. Dial gauge for 0.0001in intervals. Engine bores were big enough we used internal mics the check bores, cross checked by feel with external mics.
Check, check, check again, then confirm with a plug gauge or similar.
K2
 
Hi K2,

Thanks for your post !

Its just reminded me that I have a set of Moore & Wright internal micrometers that I haven't used for years. I must dig them out and check that they haven't started to go rusty.

Oddly enough that is what I originally bought them for, measuring cylinder bores. The cylinder hone frame and arms went in the scrap quite some time ago, as far as I recall I kept the set of five stones. Not that I can remember where they are now.
 
Hi Guys,
I have various ball bore gauges but this is not my preferred method !

This is the method that I was taught using dividers and then measuring them with a micrometer. I've used this method for years without a problem. Its also easy to detect an out of round or tapered bore. It does depend on feel though.
As a self taught toolmaker, one of the jobs I had after about a year of time was making an approximately 12" matched bore with a stepped shoulder on the mating part. With inside or outside micrometer that big I made the uncritical bore to tape measure size and then made an outside caliper like that out of a couple of pieces of sheet metal with a screw joint and made the mating part a close sliding fit. Pretty old school but it can be done with care.
 
I have been using a telescoping bore gauge for a while but don't trust my ability for accurate repeat measurements.
It is also possible that the surface finish of the cylinder affects the measurement results, the surface is too rough, it is not straight...
 
What is the minimum bore size for this tool? Thanks, ZJohn

Sunnen has made a lot of different bore gauges. The picture shows the type I had. It comes with various tips and can measure around 1/2" to 3/4" bores in the small size and up to 2" in larger sizes. Even used they are around $600 for a set.
 
Thanks for all the input! After much consideration I've decided to buy a dial gauge of ebay. Sort of an excuse to get more tools-will be my Christmas present from my wife. Will report on results when I have some.
The wide range and smallest diameter drives the price. 0.70” - 6” are around $120, but 2” - 6” run around $60. Found this one (0.70” - 1.50”, $85) may suit your needs:

IMG_6337.jpeg
 
The wide range and smallest diameter drives the price. 0.70” - 6” are around $120, but 2” - 6” run around $60. Found this one (0.70” - 1.50”, $85) may suit your needs:
Always like this M2 tap is more expensive than M6 :cool:
I buy the tools, when I think I must have them. When I "need" it I usually already forgot that I "had to have it". More important I forgot how expensive it was.
 
The smaller Sunnen gauges are expanding ball style. All need to be set. Sunnen has special fixtures, but I used a micrometer. My main interest was checking cylinder bores for roundness and taper. The larger gauges were great for this.
Lohring Miller
 
Hi Guys,

Some time ago I designed and made a three ball bore gauge, specifically designed to measure 12 to 15 mm bores. It occurs to me that people might not realise that these devices are comparative and not able to make direct measurements. From having made a bore gauge, I was surprised just how simple they can be.

I did drawings but at the moment they are on one of my several backup discs. I was going to post one on here and will when I find them.

Essentially three balls rest on a movable taper in such a way that the balls are expanded to meet a reference (setting ring) and zeroed, then the gauge is inserted into the bore to be measured. The amount that the taper moves gives you the difference between the set value and the new value. Very accurate values can be measured this way. I used a micrometer thread but a dial gauge could be used.

I found a couple of pictures, but not the drawings.

120ccb079faf63c637c8a3143269b6e9.png


This picture is looking into the gauge end in a setting ring. You can just see the end of the taper. Its just resting on a bit of wood whilst I took its picture.

deabf9c4520ffa4dbdb92b8ec066c8d1.png


The end of the bore gauge next to the setting ring.

f0e085ae674f9d296465ac72053f7d26.png


The tapered needle used to expand the three balls.
 
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Hi k2,

Thank you for your nice comment.

The hard part for me apart from finding suitable hardened steel balls, was calculating and machining the taper. It took me a little while to realise that the size of the ball and the taper angle were intimately related in order to get a linear reading.
 

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