Hello
Bead blasting is a common surface finish, particularly for aluminum parts, which can be the final finish or prior to additional protection, such as anodizing, passivation (in the case of steel) or painting. It involves projecting glass beads or other materials onto the surfaces of the treated part, in order to erase machining, cutting or other undesired traces, and to give a satin and matte appearance, very homogeneous.

Generally, this operation affects the few µm on the surface of the part, and can slightly deform the first 10µm. It is therefore common to protect tapped holes, threads and surfaces with very tight tolerances (intervals <20µm), but this is not necessarily mandatory.

When ordering a part from Xometry, for example, it is not necessary to indicate the surfaces to protect, unless this protection is known to be necessary by the customer. For very small and fragile geometric details, for example protruding shapes less than 5 millimeters wide, which could break by hand, it is advised not to proceed with this treatment, due to the pressure of the bead jet.

In terms of mechanical modifications, bead blasting will slightly increase the hardness of the surfaces, but not as much as hard anodizing, with which it can be combined, or tempering or nitriding treatments (for steels).

I hope these information can help you. We also have an article on the subject of surface finishes (here for machined parts, but some apply after other processes): https://xometry.pro/fr/articles/usinage-cnc-finitions/