BL-123 Pair of 1 x 2 x 3 Precision Steel 1-2-3 Blocks by 1-2-3 Blocks

Very sturdy and precise items. They come coated in grease and wrapped in tissue paper to make sure that they don’t rust over time. Once that’s cleaned off they’re amazing.

Tested on a surface table and very precise. Good value.

These came wrapped in oiled paper - and seemed to have been on a shelf for some time. However, they are as nicely made as I could have hoped and as accurate as I am able to measure. Recommended.

The basic specification for these 1-2-3 blocks is:Size within +/- .0002"Flatness and parallelism within .0002"Squareness on all sides is 0.0003" per inchPairs are matched to a tolerance of 0.0002"I bought these, more expensive, versions of standard 1-2-3 blocks, more for experimentation with precise measurement then any real need for such precision tools. They've already seen use, but cheaper versions would probably have done me. However, having bought them I thought I might as well see how closely they measure up.I don't have Inch specific gauge blocks, but given that imperial to metric is a very simple conversion, I used what I had (Moore & Write Grade 1 metric gauge blocks, recently calibrated, Mitutoyo Grade 1 surface block (brand new) and my trusty Mitutoyo 543-391B Digimatic Indicator) to make comparative measurements and see if these blocks fall into spec'The long and the short of it is that, within the bounds of my amateur measurements, they certainly did.As you can see from the recorded measurements (photo attached) the 2 inch axis of both blocks fell outside of the published specifications, but the reality is that we're talking about fractions of a tenth (0.0001") which is, without question, way outside of the accuracy that I can claim to be able to measure.I don't have any tools that will accurately measure squareness, but I do have a precision Moore and Write engineers square to check the blocks with, and I couldn't find any issues on visual inspection.The chamfering on the holes and the block walls is far from fabulous, and I would have preferred better concentricity on the hole chamfers and a deeper cut, but otherwise the finish of the blocks is very good, so no complaints there.The only real issue is one that maybe 95% of all blocks of these type have, which relates to the inherently poor design. Specifically, the non-threaded holes are not big enough to allow a 3/8-16 threaded bolts clearance.The upshot of this is that bolting these blocks together, to make a right-angle shape for example, can't be achieved with a standard 3/8-16 threaded bolt or screw. So annoying!You can just about do it with an M6 bolt/nut which will facilitate this, but the countersink on the holes isn't deep enough to allow this technique to leave a flat surface with a standard countersink M6 bolt. Why doesn't anyone manufacture 1-2-3 blocks with clearance holes of a suitable size?In any case, while I might splurge on a cheap set of 1-2-3 blocks for comparison, these more expensive BL-123 blocks do what they said they would within the nominal tolerances published, with a reasonable finish.They took a while to get here, but very happy with my purchase.

Nice piece kit , Top Quality

Very good quality

More than adequate

Modelmaking