Precision 1-2-3 blocks....

[Nelson]

So this is the 1-2-3 block set from Brown and Sharp that I bought from the seller for $11 who did
not ship them till I made a stink. They are missing two screws.

They are called "Ultra Precision blocks" as you can see. What makes them "ultra precision"?



View attachment 31899


Nelson

 

[Tony Wells]

They are parallel and square within a couple of tenths. Not that they are exactly 1.000 x 2.000 x 3.000 necessarily. That's why you shouldn't use them to check your micrometers. You don't know for a fact just exactly what size they are. They are furnished a little oversize so those who wish, and have the capability to grind or lap them can bring them pretty close to 1 x 2 x 3. But only if you can measure and verify to the degree of accuracy you need or want.

 

[Tommie D]

"What makes them "ultra precision"?"

I'm guessing it's the way they are ground to close tolerances. Here are a few spes's I found on them.
Each block precision ground on all 6 surfaces.
Case hardened to HRc 50 - 60. Surface finish from 6 to 16 micro inches. Squareness on all sides to within .0001". (23) Holes: (5) 3/8"-16 tapped; (18) untapped thru holes Oversized to allow for nominal lapping .0001"~.0003".


For $11 you got one heck of a deal!