Precision CNC Machining

Many suppliers use 'precision' as an adjective. Here it is defined by equipment and process: the factory's equipment list includes a CMM coordinate measuring machine, and the quality system behind production is certified to ISO 9001 and IATF 16949. A precision part, in this house, is a part whose critical dimensions are measured on calibrated equipment and recorded — not a part that merely came off a good machine.

This page deliberately publishes no tolerance numbers. The manufacturer's own product data does not state them, and inventing a tighter-sounding figure would be marketing, not evidence. What can be promised — and evidenced — is the inspection infrastructure and the procedure: critical dimensions identified at review, an inspection plan built around them, and CMM verification before release. Buyers with specific tolerance requirements should put them on the drawing; the review will confirm, feature by feature, what production and inspection can hold.

Precision is decided before the first chip: in fixturing, in operation order, and in which features are machined in the same setup so their relationship is guaranteed by the machine rather than by re-measurement. The machining division's equipment — machining centres, milling machines, lathes, wire-cutting for fine profiles — supports that planning, and the DFM review is where a part's precision strategy is set.

It is also decided by honesty about process choice. Some features belong to machining; others hold better when cast, drawn or extruded and then finish-machined. A factory with five processes can say so without losing the order, which makes its precision advice worth more than a single-process shop's.

The cheapest precision is selective precision. Mark the dimensions that govern fit and function as critical — those get the inspection plan's full attention — and let general dimensions follow standard drawing practice. Blanket tight tolerancing across a whole drawing raises cost on every feature, including the ones whose variation nobody will ever notice. The review will point out where a flagged dimension looks tighter than its function needs; relaxing it is your decision, priced transparently either way.

Machining programmes stay healthy on two habits. First, keep the drawing and the inspection plan married: the dimensions flagged critical at review are the dimensions the CMM programme measures, so a drawing revision should always travel with a note about what changed functionally — production will re-plan operations and inspection from it. Second, protect the starting-point decision. As quantities grow, a part begun from bar may deserve re-examination as an extrusion- or casting-based part with finish machining only; the review re-opens that question at volume milestones rather than letting a prototype route harden into a production cost.

Buyers transferring an existing part should say so at enquiry. A part proven elsewhere, a part needing re-specification from a sample, and a brand-new design are three different projects with three different first steps, and the review will name which one you have before quoting anything.