Shars 6" Fully Machined Threaded Back Plate 1-1/2-8 for 3 or 4 Jaw Self Center Chuck 202-6109 S

Does not screw onto the thread size it should fit, looks like it has been in a lathe chuck and double threaded.

No issues with this product.

Threads fit correctly, mounting holes correctly located and there was enough material to machine the registration shoulder concentric to my lathe.

As some others have commented, the axial runout is pretty bad, 0.025" on the one I got. But, since you have to turn down the mounting shoulder anyway, a truing pass over the face isn't all that big a deal. So, I would call it 'mostly fully machined'. It appears that the cause is the center bore not being all that perpendicular to the axis. Still, you need one to mount the Shars chucks, and it's a lot easier than machining one up yourself. For the price, totally acceptable.

The order arrived on time. The lathe back plate is made from cast iron which does not machine very well, but it will do. the tolerances are as specified so it will suite my purposes.