Tool accuracy

[Rhossydd]

Judging from some of the posts above I wonder if some people don't know how to use a vernier?

I'm sure we all know how to read a vernier, but are smart enough to know a big digital display is easier to read and less prone to error.
In the same way few people would bother to use a slide rule if they could use an electronic calculator.

 

[CHJ]

Since ball bearings need to be very similar to each so that each takes an equal load they are manufactured to quite amazing tolerances,

Going to be rather pedantic here but Ball Bearings, and roller for that matter are not manufactured to close tolerances.

Basically you take rough ground balls of steel, ground in horizontal grinding wheels much like old fashioned corn grinding.
You take a couple of buckets full of these rough blanks and but them in a glorified cement mixer, You add rough balls of various sizes, say 5mm to 60mm in a mix that gives an optimum contact area.
Add some water, soda and a grinding medium and spin until all polished nice and shiny and round.

Then you pass them though a gauging system by rolling them down a ramp, old days used to be air gauges, presume they use lasers these days, and select balls of the same nominal size into differing sets,
It's at this stage where accuracy comes into the task, a nominal 10mm ball may end up with 10 or more different sets.

These sets, 10mm + a nats say, are married with inners and outers that have likewise been selected into sets, you can't grind them to a finite size so have to select them when finished, so that the finished assemble meets the clearance tolerances.


So that as you say a 1/4" or 5mm ball may be more than accurate enough for a everyday workshop reference once selected and checked be aware that they may differ in size (metrology levels) if taken from two different ball races of the same part number and specification

 

[Jacob]

..., but are smart enough to know a big digital display is easier to read and less prone to error.

Easier to read but the error is less certain

In the same way few people would bother to use a slide rule if they could use an electronic calculator.

Not really equivalent. A vernier calliper is a simple one-function slide rule but is more or less indestructible in the workshop or tool box and will always be useful. In fact a simple steel slide rule might be a good idea - just a few functions like basic trig, weights and measures conversions. Surprised Veritas haven't come up with one. We have roofers squares, and most tapes are marked out with other mystical marks, so the idea is already in use.

 

[joethedrummer]

Hey,,,, How did NASA get anywhere near the Moon? ,,Let alone on the edge of the Suns planetary system,,, With a 12 inch ruler?? ,,,things have moved on,,,,Keep up!!!
But if you are creating with WOOD ,,??

 

[AndyT]

Hey,,,, How did NASA get anywhere near the Moon? ,,Let alone on the edge of the Suns planetary system,,, With a 12 inch ruler?? ,,,things have moved on,,,,Keep up!!!
But if you are creating with WOOD ,,??

Six inches actually.

http://historical.ha.com/c/item.zx?saleNo=669&lotIdNo=41035

 

[shed9]

Hey,,,, How did NASA get anywhere near the Moon? ,,Let alone on the edge of the Suns planetary system,,, With a 12 inch ruler?? ,,,things have moved on,,,,Keep up!!!
But if you are creating with WOOD ,,??

Six inches actually.

http://historical.ha.com/c/item.zx?saleNo=669&lotIdNo=41035

How the hell did they operate that with those space gloves on? Come to think of it, how did they operate them Hasselblad's as well........ I'm starting to doubt those moon landing things now. :lol:

On the ball bearing gauge thing. I do a little metalworking (bridgeports, that sort of thing) and have used in the past full bearing units as parallels, they are just as accurate as purpose parallels and are machined to very fine tolerance (unlike the inner balls).

If you want a reference and have some clean bearings, this is a good start.