What is finishing?

Finishing, also called surface treatment or post-processing, is the umbrella for processes that change a part's properties after machining. It covers surface treatments such as anodising, zinc plating, electroless nickel plating, passivation, powder coating and painting, mechanical treatments such as blasting and vibratory finishing, and in shop usage often heat treatments such as hardening and stress relieving. A finish provides, for example, corrosion protection, wear resistance, hardness, a colour or a particular surface texture. On the drawing it appears as a note, a reference to a standard or an indication on one face.

What does finishing do to size and surface?

Many finishes change the size. A plated or chemical layer builds up on the surface, an anodic layer grows partly into the material and partly outwards, and hardening can cause distortion and dimensional change. Layer thickness also varies across the part, for example at edges, in bores and in threads. Roughness can change too: blasting gives a matt surface, and a layer follows the surface beneath without being identical to it. So the drawing should say whether sizes and roughness apply before or after the treatment, and which faces are masked.

How does finishing work in practice?

A finish helps decide the order of the route. If it sits in the middle, such as hardening before grinding, the part needs stock allowance and an operation follows the treatment. Size-critical faces and threads get a correction beforehand or are masked. Many machining shops send finishing out. The finisher's price often depends on quantity, area or weight, with a minimum charge per batch, and the finisher's lead time comes on top of the delivery time. On small quantities that minimum can set the price per piece.

What is finishing often confused with?

Finishing as a treatment is not finish machining: finish machining is the last cutting pass to size and roughness, a finishing treatment is a separate process after it. In English the same word covers both, so check which one a drawing note or a quote line means. Nor is finishing a roughness requirement: roughness is a requirement on the surface that can come from machining or from a treatment.

How do you see finishing in Blake?

In Blake the finishing sits with the part as a proposal from the drawing, beside material, tolerances, roughness and threads. You confirm or correct it; who did so and when stays visible. A subcontracted treatment is its own line in the estimate, priced from your own subcontract library; if that price is missing, the line stays open. More on estimating.