The bracket rocks until we tighten the clamp

There are three bottom pads and a continuous ledge along one side. The ledge looks like it might touch the bracket's inside radius.

That radius is worth a look

Check the actual samples and ledge for burrs too. Don't assume a clash in the design if a raised edge is holding just some parts up.

Yes, look before grinding anything away

Nothing altered. Toolmaker is coming to check the contacts. The rocking follows particular brackets, not every sample, which is what made me hesitate.

Have you kept the sample identities with your observations? It would help to compare the same rocking and stable brackets during the toolmaker's visit. Otherwise the useful difference can disappear into a box of similar parts.

Take the clamp out of the argument for that first seating check, under the toolmaker's bench method; clamping it flat can hide where it catches

Are those samples from the same machining batch? If the inside radius varies between batches, the drawing and sample measurements together may help explain why only some touch the ledge.

Two batches. I kept them in separate bags and marked which ones rock, so the toolmaker will have both groups.

That is enough to make a useful comparison. Include the drawing revision supplied with each batch if you have it, since a sample difference may have an intended explanation.

Same drawing revision on both delivery notes. I've put those with the samples. Thanks for the reminder, I would have left them in purchasing.

And just to be clear, we haven't measured the radius difference yet. I only know which samples rock. Don't want my guess turning into the cause by the time the toolmaker arrives.

Fair enough. Let the contacts tell you