A screw machine part is only as good as the tolerance callouts on its print. We explain how size, features, material and process decide what a turned part can hold — and what each step tighter actually costs.
Most rejected turned parts fail on the print, not the machine. These four patterns come up again and again.
Blanket tight tolerances across the whole drawing push cycle time up and scrap rate with it. Only two or three features on a typical screw machine part actually need that band. The rest can breathe, and the part cost drops with them.
A position callout measured from a turned face that is itself ±0.05 mm moves the true position with it. Two stacked tolerances can eat a third of the available band before the tool touches the bar. Pick a clean datum and hold it first.
A 3 mm diameter over 60 mm deflects under cut pressure. Callouts written as though the part were a solid block will fail on a lathe no matter how good the machine is. Support, reduced depth of cut or a second operation decides whether the number is reachable.
±0.005 mm means little if the surface is left at Ra 3.2 μm or the inspection method is a caliper. State the finish, the gauge and the measurement temperature, or the first article will argue about method instead of dimension.
Four variables decide what a screw machine part can hold. We work through them before quoting.
A screw machine part under Ø25 mm with short, well-supported features is the easy case. Turned diameters, shoulders and through holes on that scale hold ±0.005 mm on our Swiss-type and mill-turn centers without drama. As the length-to-diameter ratio grows past roughly 5:1, deflection and chatter take over and the practical band widens.
Feature type matters as much as size. A turned OD is a continuous cut and holds tightly. A cross-drilled hole, a milled flat or a slot made on the same part is an interrupted cut with its own setup error. We separate the two on the print so each carries the tolerance it can actually achieve.
We check six or eight critical dimensions in process rather than trusting the first article alone. That catches drift from tool wear before the run is half done.
Free-machining grades are forgiving. Brass C36000 and stainless 303 cut cleanly, hold a sharp edge and let us hold tight bands at normal feeds. Ductile materials behave differently: 316L and 17-4PH work-harden at the cut and push back on the tool, and titanium TC4 (Ti-6Al-4V) springs away from the insert. The same tolerance costs more in those grades.
Process choice follows from there. A dedicated screw machine or Swiss-type lathe with bar feed is the right answer for high-volume small parts. For prototype and low-volume work we run the same geometry on mill-turn centers with live tooling, so a cross hole or flat comes off in one setup instead of two.
Use this as a starting point. The right band depends on the specific part, but these are realistic turning targets.
| Feature | Typical Band | Notes |
|---|---|---|
| Turned OD, short, rigid | ±0.005 mm | Free-cutting grades, supported length |
| Turned OD, long slender | ±0.02–0.05 mm | Above 5:1 ratio; deflection dominates |
| Bored or drilled hole | ±0.01–0.02 mm | Reaming tightens to ±0.005 mm |
| Cross hole or milled flat | ±0.02 mm | Interrupted cut, live tooling setup |
| Shoulder face position | ±0.01 mm | Datum from a turned face |
| Surface finish, turned | Ra 0.8–1.6 μm | Ra 0.2–0.8 μm on request |
| Thread pitch diameter | Class 2A/2B | Class 3A on request |
| Concentricity, two diameters | 0.01 mm TIR | Same setup, single chucking |
Turning is the core. These are the operations that usually ship with it.
Bar-fed turning plus live tooling for cross holes, flats and slots. One setup keeps concentricity tight and removes a second-op error source.
For screw machine parts with angled ports or compound features that cannot be reached on a two-axis lathe. 16 simultaneous 5-axis centers.
First articles and fit checks before committing to a bar-fed run. Useful when the tolerance question is still open.
Anodizing, electroless nickel, zinc and silver plating, passivation, bead blasting and laser marking down to 1.5 mm character height.
Raw material check, in-process monitoring and final inspection on 100% of parts. Dimensional reports on request.
Turned parts combined with purchased components and packed to your line sequence, so the shop floor does not open bins.
| Item | Range | Included |
|---|---|---|
| Part diameter | Ø0.5–65 mm typical | Yes, standard |
| Maximum length | 4,000 mm | Yes, shaft-type work |
| Tolerance floor | ±0.005 mm | Yes, on qualifying features |
| Surface finish | Ra 0.2–3.2 μm | Yes, specified on print |
| Materials | Aluminium, stainless, steel, brass, titanium | Yes, 40+ grades |
| Order quantity | No minimum | 1 prototype to 10,000+ parts |
| Inspection | 100% before shipment | Yes, reports on request |
| Quotation | Within 12 hours | Free DFM analysis included |
A tolerance figure is a promise. These are the numbers behind ours.
Our tightest held band on qualifying turned features, verified in process rather than assumed from the first article.
Operating since 2011, with the process knowledge that comes from running the same part families year after year.
Sixteen simultaneous 5-axis centers, twelve four-axis mills and sixteen mill-turn centers under one roof.
Parts that pass final inspection on the first submission, measured across our production output.
Drawing in, quotation and a free DFM analysis back within 12 hours. Production can start within 24 hours.
ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022 cover quality, automotive, medical and data security.
Sensor housings, fittings and connector bodies turned from 303 and 6061, with IATF 16949 process control behind them.
Small stainless and titanium components where burr control and cleanability matter as much as the dimension.
Bushings, pins and hydraulic fittings turned from 17-4PH and 4130, with material traceability and inspection reports.
Gear blanks, shafts and pivot pins where concentricity across two diameters decides whether the joint runs quiet.
On a short, well-supported turned diameter in a free-cutting grade, ±0.005 mm is realistic. That is our tightest held band, not a blanket figure.
The band widens as the feature gets longer, more interrupted or made in a work-hardening material. A 3 mm diameter over 60 mm in 316L will not hold the same number as a 10 mm shoulder in brass. Send the print and we will tell you which features can carry which band.
When the fit does not need it. A clearance hole, a cover register or a cable pass-through rarely needs ±0.01 mm. Tightening those features adds cycle time, more tool changes and more scrap without improving function.
Keep the tight band for the two or three features that set the fit, the alignment or the seal. Everything else can sit at a general tolerance and the part gets cheaper.
Yes, and often by more than the machine does. Brass C36000, stainless 303 and aluminium 6061 cut freely and hold tight bands at normal feeds.
316L, 17-4PH and titanium TC4 work-harden or spring away from the tool. The same callout costs more in tool wear and time, and the practical band can be two or three times wider.
Put both on the print. A ±0.005 mm diameter meant to run in a bearing needs a finish to match: Ra 0.2–0.8 μm for a sliding fit, Ra 0.8–1.6 μm as a general turned finish.
If the finish is left unstated, the default as-machined condition is Ra 1.6–3.2 μm. That is fine for most clearance features and wrong for a sealing surface.
We check raw material on receipt, monitor dimensions in process and inspect 100% of parts before shipment. Critical features are measured with the gauge named on the print where one is called out.
Dimensional reports are available on request. If you have a specific measurement method in mind, say so at quoting stage so the method is agreed before the first article.
Bar-fed turning pays off once setup is amortized, which usually means a few hundred pieces upward. Below that, the setup cost dominates the piece price.
We run no minimum order quantity, so a single prototype is available, and the same geometry can run on a mill-turn center for low volume before moving to bar feed at higher volume.
A 2D print with the critical dimensions, datums and finish callouts marked, plus a 3D model if one exists. The print is what the part is judged against, so it should carry the tolerance, not the model.
If the print is incomplete, we flag the gaps in the DFM analysis that comes back with the quotation.
Uploads are handled as confidential, and we hold ISO 27001:2022 for information security. A non-disclosure agreement is available on request before any file is shared.
We do not share customer drawings or part geometry outside the quoting and production team.
Upload your drawing and we will return a quotation with a free DFM analysis within 12 hours, including which features can hold which band and where a looser callout would save money.
12-hour quote100% inspectionNo minimum orderNDA on request
Trusted by engineers and manufacturers worldwide
Upload your 3D model or 2D drawing and get a quotation with a free DFM analysis. Maximum processing size 4,000 mm.
CNC Metals 13 grades
CNC Plastics 10 grades
Machines & processes 12 options
Surface & post-processing 10 options
Material: not selected Machine: not selected Post-process: not selected
Fill in this short form and we'll open WhatsApp with your message ready to send. We only use these details to reply to you.
Nothing is sent until you press send inside WhatsApp.
