Austin Precision CNC Machining Service: What Engineers Should Check Before Ordering

A tolerance callout is a contract about one feature at a time, not about the whole part. When we quote austin precision cnc machining work at ±0.005 mm, that number applies to specific dimensions you name, measured in a controlled room at 20 °C with the part fixtured the same way it will be inspected. The rest of the drawing still needs a general tolerance block, usually ±0.1 mm on non-critical faces.

Heat is the usual reason a tight callout fails. Aluminum 6061 grows about 23 μm per meter for every 1 °C of temperature rise. A 300 mm bracket that warms 5 °C during roughing has already moved 0.035 mm before the finish pass starts. Rough, let the part cool, then finish. That single pause is often the difference between a passing first article and three rework cycles.

Not every feature deserves ±0.005 mm. Bearing bores, dowel pin holes, sealing faces, and mating spigots do. Bolt clearance holes, chamfers, and outer profiles usually do not. Tagging the whole drawing tight multiplies cost and inspection time without adding function, and it makes a real problem harder to spot when one appears.

Five-axis matters when a feature cannot be reached without repositioning the part, or when one setup keeps several faces in the same datum. Impellers, turbine housings, medical bone plates with compound angles, and hydraulic manifolds with ports on five sides all fall into that group. We run 16 simultaneous five-axis machining centers for exactly this class of work.

A flat plate with holes on one face does not need five-axis. Neither does a simple shaft. Those parts run faster and cheaper on our 27 three-axis machines or 16 mill-turn centers, and moving them to a five-axis spindle only adds setup time. The honest answer is sometimes that the cheaper machine is the correct machine.

Judge by setup count, not by feature count. If a part needs three or more setups on a three-axis machine, and each setup carries a positional tolerance of ±0.02 mm or tighter against the others, five-axis usually wins. One setup removes the stack-up between operations entirely.

Size also sets the limit. Our largest travel is 4,000 × 400 × 150 mm, with 750 × 1,150 × 550 mm and 600 × 600 × 600 mm platforms for mid-size work, and Ø400 mm rotary tables for round parts. Anything outside those envelopes gets split into sub-assemblies or moved to a different process.

Aluminum is the default for prototypes and most housings. 6061 and 6061-T6 machine cleanly and hold ±0.005 mm well. 7075 gives higher strength but chips harder and can stress-relieve after heavy material removal, so leave stock and take a light finish pass. 2024 behaves similarly and is common in aerospace brackets.

Stainless brings different problems. 303 is the free-machining grade and the easiest to run. 304 and 316 work-harden if the tool rubs instead of cutting, so feeds stay aggressive and depth of cut stays consistent. 17-4PH (SUS630) holds tight tolerance after heat treatment but needs allowance for the shrinkage that comes with it.

Titanium TC4 (Ti-6Al-4V) and Inconel cut slowly and generate heat at the edge. Tool life is short and cycle time is long, so we plan the process around heat removal rather than speed. Magnesium AZ31B and AZ91D machine fast but require chip control and fire-safe handling, which is a shop discipline, not a machine setting.

Plastics behave on their own terms. POM and PEEK hold dimension well; ABS and PP flex under clamping and need lighter fixtures. Carbon fibre eats tooling and needs dust extraction. Tell us the material and the finish you want early, because both change the toolpath we write.

As-machined surfaces land around Ra 1.6–3.2 μm and are fine for brackets, fixtures, and internal parts. Functional sealing faces and bearing seats usually want Ra 0.8–1.6 μm, which means a finishing pass with a smaller stepover. Optical and vacuum surfaces may need Ra 0.2–0.8 μm, and that is a different setup and a longer cycle.

Specify finish by function, not by habit. Calling Ra 0.2 μm on a part that sits inside a cabinet adds cost with no benefit. Calling Ra 3.2 μm on a sealing face invites a leak. We would rather ask what the surface does than guess from a default note.

Post-processing changes dimensions, so sequence matters. Anodizing adds a few micrometres per surface and grows a bore smaller. Hardcoat adds more. Electroless nickel and plating also build up. If a bore is held at ±0.005 mm and the part gets coated, tell us before we cut, because we machine to the pre-coat size and note it on the traveler.

We cover anodizing in clear, colour, hardcoat, and conductive types, plus electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing, and polishing. Laser marking is available down to 1.5 mm character height. Grinding and deburring run alongside these when a drawing calls for them.

Every part gets inspected before it ships. That means incoming raw material check, in-process monitoring during the run, and a final inspection against the drawing. Inspection reports are available on request, and first article reports are standard for new parts. We hold ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022.

A useful quote lists the process, the machine class, the tolerance it can hold, the material, the finish, and the lead time. If a quote is a single number with no process note, it is hard to compare against another. Send the drawing and we return a quotation plus a free DFM analysis within 12 hours. That analysis often points out a feature that will not machine as drawn.

Volume does not change the entry point. There is no minimum order quantity, so a single prototype and a 10,000+ part run go through the same quotation path. Uploads are handled as confidential, and an NDA is available on request if your program needs one in place before files move.

Lead time is quoted per part, not promised in advance. As a general guide, production can start within 24 hours of a released order and parts typically ship in 3–5 days. Complex five-axis work with coating or tight inspection adds time. We would rather quote a realistic date than a fast one we cannot hold.