MSC has them for just a little lower than those prices. Page 1661
I paid 19 and ?? and 25 about 10 years ago. The second one didn't have a price tag still on it! Got mine at J&L floor room book rack in San Jose Ca. Long since closed.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
I don't know what kind of tolerance you are looking for, but if you throw a good piece of drill stock (tool steel dowel) in the bottom of a machine vise to allow it to let a block rock flat against the head jaw (dialed in, of course) and surface it with a sharp, good flycutter and climb mill back on the second pass, keep rolling the block in the same direction each time you cut a new surface, you should have a block square to .00001 in every dimension. You can finish the two sides by using an endmill while the block is still in the vise, if the block is long enough to give you clearance that way; again, by climb cutting gently so the pressure is again supported by the solid machine vise jaw, you should have a righteously square block. If you choose to grind it, the key is to keep rotating it in the same direction each time you move to the next surface. In my experience, after doing all that, most times if it's out of the spec you want, it was from from grinding with inappropriate or poorly dressed wheels, and I've seen people ruin a lot of good parts from overzealousness lapping, too. I know one of the rites of passage of being a "real" machinist/tool maker is making a square block with a file, but... heh
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