In article ,
Rich Grise wrote:
On Thu, 21 Jul 2005 22:24:11 -0400, DoN. Nichols wrote:

In article , Rich Grise
wrote:

[ ... ]

410: 1-2-3 block, or Johansson block

[ ... ]

Thanks for the correction.

You're welcome.

My office opens onto a machine shop, and I
hear the terms - I'd heard of Jo blocks before, as you described, but
the guys around here sometimes call gage blocks "jo blocks";

That is because their inventor was Carl E. Johannsson (I'm not
sure that I have the right number of 'n's and 's's in that name), and he
was hired to implement his set of reusable standards at Ford many years
ago. Brown & Sharpe gauge blocks are still marked with his full name,
or on the smallest just "C.E.J".

Starrett sells a different line, marked "Webber", which I
presume started when the patent that Johannsson had ran out. Both are
excellent sets. But "Jo blocks" tends to be used even when they are
marked "Webber". :-)

albeit
I've never heard anybody refer to a 1-2-3 block as a "jo block"; I
made that up all by myself. ;-)

While a good 1-2-3 block is quite accurate, they are not as
accurate as gauge blocks. Even the cheap Chinese ones are supposed to
be accurate to 0.000050" (50 micro-inches), and the best (and most
expensive) of them are as good as (I think) 0.000002" (2 micro-inches).
At that kind of accuracy, the thermal expansion from the heat of your
hand when you hold a "Jo" block too long will introduce errors.

Although, the 1-2-3 blocks around here that have holes in them,
have holes all the way through. Hmmmm....

Agreed. I've never seen ones with blind holes, which makes me
wonder about the item in the posted puzzle set.

Enjoy,
DoN.

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