Buyers assume "advanced CNC technology" automatically means tighter tolerances. In practice, the effect depends on which process and which feature carries the critical dimension. A four-axis turned brass bushing behaves very differently from a five-axis milled titanium shaft.
Brass and copper parts hold ±0.01 mm on turned diameters at steady cutting speed. The same tolerance on a knurled section or a drilled hole in stainless steel 316L pushes cost up noticeably. Aluminum forgives more, but surface finish on thin-walled sleeves still needs attention.
The risk concentrates at threaded inserts and small-diameter pins. A 4 mm OD brass insert nut leaves almost no room for chip evacuation during internal threading. Without a specified thread class or burr-free chamfer, the inspection report flags parts that pass functionally but fail dimensional checks.
Ask for thread-gauge results and a CMM report on the two most critical datums. For batch runs above 500 pieces, a first-article inspection report with photos saves a week of back-and-forth when a drawing revision slips.
Weeda Precision supports drawing-based CNC turning, prototypes, and batch production with revision tracking. Under 10,000 pieces annually, a two-week sample lead time is realistic; multi-axis milling of sensor housings in stainless steel stretches to four–six weeks.
In automation equipment and electronics assemblies, OEM precision parts like stainless steel bushings and custom fasteners with knurled tails shift the quote by 20–35 percent depending on process. Plastic molding tools that clamp onto machined pins are a common pairing.
In your RFQ, state material grade, surface finish in Ra, and whether a thread-gauge report is required per lot. List the drawing revision number and packaging method. That one step reduces quote variance significantly.
If you are re-quoting an existing part, send the current drawing plus one failed sample photo. A short call to identify which tolerance actually moved the price will save you from paying for CNC capability you do not need.