Articulating arms, bearing sources, FREE gauges! A three-fer!

[Toolmaker51]

I have only removed a bearing very rarely. I can see how the races make parallels, but how do you use 12mm bearings, to test flatness of a surface gauge? How does the convex profile make a surface gauge? Kind regards.

Phillip and I await conversion of convex to surface gauge. (what? no emoji for drumming fingers? an outrage!). Yet despite entirely different timezones, we consume popcorn in precise synchronization.

Meanwhile a couple handfuls of same size balls are just two pieces of flat plate short of rolling parallels, just the ticket for rough material on a bandsaw. Drill barely over ball diameter all the way through or partially, drop one in place lightly stake the circumference. Occasionally, the craftsperson will affix a cover plate to one [up] side. They can also be made that way with BB size spheres, the holder plate sandwiched twixt 2 plates with small holes, but rather tedious.
And then tedium interferes with posting on HMT.net........

Balls also figure in surface flatness readers, providing 3, low friction, minimum contact feet distributed beyond indicator tip. A few posted herein.
Printers use these to get a machine table [such as a paper cutter] dead flat with infeed and outfeed tables. Just zero on one table, adjust other into plane per readings of the 'indicator slide'.

[Philip Davies]

Phillip and I await conversion of convex to surface gauge. (what? no emoji for drumming fingers? an outrage!). Yet despite entirely different timezones, we consume popcorn in precise synchronization.

Meanwhile a couple handfuls of same size balls are just two pieces of flat plate short of rolling parallels, just the ticket for rough material on a bandsaw. Drill barely over ball diameter all the way through or partially, drop one in place lightly stake the circumference. Occasionally, the craftsperson will affix a cover plate to one [up] side. They can also be made that way with BB size spheres, the holder plate sandwiched twixt 2 plates with small holes, but rather tedious.
And then tedium interferes with posting on HMT.net........

Balls also figure in surface flatness readers, providing 3, low friction, minimum contact feet distributed beyond indicator tip. A few posted herein.
Printers use these to get a machine table [such as a paper cutter] dead flat with infeed and outfeed tables. Just zero on one table, adjust other into plane per readings of the 'indicator slide'.

Popcorn? I have no appetite for popcorn, nor any use for emojis as an aid to communication. Thank you. The links you provide below are helpful, however. I have a surface plate, it’s probably very worn, the late owner’s rule was perceptibly hollow from use.