Most CNC machined part orders fail at the drawing stage. For precision bushings, the gap between a 0.5 mm wall on paper and a part that actually seats cleanly in a housing is where procurement teams burn time and budget. The spec sheet needs to say far more than outer diameter and length.
What Material Fits Your Precision Bushings
Brass and copper dominate for threaded inserts and bushings in electronics housings and automation equipment, because they machine clean and resist galling under repeated assembly cycles. Bronze handles the higher-temperature duty in automotive assemblies. If the bushing will sit inside a plastic molding tool, a stainless steel bushing or a precision turned part in 6061 aluminum keeps the cycle stable and reduces wear. Match the material grade to the thermal and chemical environment, not just the catalog default.
Wall thickness tolerance is the dimension that kills a fit. For a 6 mm ID bushing, holding the bore at ±0.01 mm keeps the mating pin or shaft from rattling. Specify ID, OD, and length tolerances as separate callouts on the drawing. A generic "±0.05 mm all around" line gives the machinist too much freedom on a critical dimension. Threaded inserts in brass or copper need a thread gauge check at both the 1st and 3rd point to confirm proper engagement before the lot ships.
How to Inspect Precision Bushings Before Delivery
Request a dimension report with micrometer readings on ID, OD, and length for every unit in the sample lot. Burr control on CNC turned parts matters more than most buyers expect; a 0.1 mm lip on the bore edge will scratch a sensor shaft or a medical device pin. Weeda Precision includes a first-article inspection package with photographic evidence and thread gauge results for each batch, which shortens the acceptance step for OEM teams.
In your RFQ, attach the latest drawing revision number, state the annual volume, and flag whether you need 10 or 100 prototype samples before the batch run. Note packaging: loose brass bushings in a bulk box will arrive dinged, so specify individual blister cells or foam trays to protect the surface finish. A 5,000-piece run of custom CNC machined parts typically hits the floor in four to six weeks once tooling and material are confirmed.
Before you send the next RFQ, pull the last three revision drawings, mark every critical-to-fit dimension with its tolerance, and name the exact material grade. That one pass through the spec sheet prevents most rework loops on small precision machined parts and keeps the line running on schedule.