Ultra Precision 1-2-3 Blocks Set with Screw Matched Pair 23 Holes .0001" Squareness Hardened Steel 1"x2"x3" Blocks Set Setup Blocks Industrial Tools w/Plastic Case

Recently got a precision caliper and, just as a test, measured these blocks. The caliper is supposed to be accurate to 1/1000 of an inch and these measured 1.000"x2.000"x3.000". Very impressed.

These do measure 1.000, 2.000 and 3.000 inches across them over entire surface between holes so the surface grinding was after other treatments. The screws fit into some threads and make them moderately useful for a couple configurations if you don't mind the screw heads. I only use by stacking the sizes I need together in a fixture then clamping externally rather than using the threads so i do not know if that stress would warp them or not.

I use these in a lot of places. my wife confiscated my first set for use in her craft room to hold down various things. I use them assembly of small items, spacers, weight for gluing projects, etc.

If you weld or fabricate any cat and milk stuff you need these blocks

The threaded holes are not threaded correctly. I attempted to run a 3/8-16 tap through one hole to clean up the thread but had to stop in fear the tap was going to snap.I will be contacting the seller about the quality issue at hand.

Holes are threaded in a checkerboard pattern. Bolts and an Allen wrench are included. And they all fit into the blow-molded case.The blocks are square and machined very well.These 1-2-3 blocks are the most versatile type when comparing to the most common 3 types: solid, spaced holes and this type which has spaced holes and spaced threaded holes. Mine that I've had forever are the spaced holes variety--no threaded holes on my old ones.The case is nothing special nor very robust. But for storage of the blocks and accessories (bolts, wrench), it works and will be fine.If you're looking at these for the versatility, you'd be correct that these will, for the most part, work where the other types of 1-2-3 blocks would. The solid blocks working better when you need them in particular situations where the holes may actually be a negative.This is a good set. Works for quick measuring and squaring up.

I've seen videos on how helpful 1-2-3 blocks can be for woodworking (checking blade squareness, depth gauge, handy square, etc.) so I thought I'd pick this set up. On my calipers they register within .0005 of 1,2,3 inches. That's more accurate than is ever needed for woodworking. I also like they come in a case for storage. I don't think I'll ever use the included bolts, I think those are more of use for machining but they are there for those who need them.Note, the blocks come in shipping grease so they need some cleanup before use (I used acetone which seemed to do well).Overall, I'm happy with these blocksitem: Nakkaa Ultra Precision 1-2-3 Blocks Set with Screw Matched Pair 23 Holes .0001" Squareness Hardened Steel 1"x2"x3" Blocks Set Setup Blocks Industrial Tools w/Plastic Case