Job startup guide

How to Start a Job With a CNC Machine Shop

This guide is for design engineers, hardware startups and procurement teams who need to start a job with a CNC machine shop without losing a week to email. It walks through the seven steps from drawing to first article, with the tolerance, material and inspection decisions that actually change the quote.

Get Instant Quote Talk to an Engineer

±0.005 mm toleranceQuotes in 12 hoursNo MOQNDA on request

On this page

Key takeaways

Send a 3D model plus a 2D drawingSTEP or IGES for geometry, PDF for tolerances, datums and finish callouts.

Ask for DFM before you ask for priceA free DFM pass catches thin walls, deep pockets and unreachable features.

Tolerance drives cost more than materialTightening one bore from ±0.05 mm to ±0.005 mm can add a finishing operation.

Confirm the datum scheme in writingIf the drawing datum and the fixture datum disagree, the first article will too.

Plan for a first article, not a full runCut one or two pieces, measure, then release the rest of the batch.

Steps 1 and 2

How to Start a Job With a CNC Machine Shop: Files and DFM

To start a job with a CNC machine shop, the shop needs two things: a solid model and a drawing that says how tight the part has to be. Send STEP or IGES for the geometry. Send a PDF drawing for tolerances, datums, thread callouts and surface finish. A model alone tells us the shape. It does not tell us which bore is a bearing seat and which one is clearance.

Name your files so the revision is obvious. Part-number_rev-C.step prevents the classic mistake where the shop cuts rev B while your team is already reviewing rev C. If the part has a mating component, send that too. A housing and its cover are easier to quote together than apart, because we can check the fit and pick one setup for both.

Then ask for DFM feedback before you ask for a price. A design-for-manufacturing review checks wall thickness, pocket depth, tool reach, corner radii and thread depth. On a 5-axis part, we also check whether the tool can reach the feature without a special fixture. Most DFM notes come back the same day, and they are free.

Keep the first message short. Part quantity, material, finish, target date, and the two files. That is enough for a quote and a DFM note within 12 hours. Long email threads usually mean the drawing is missing a callout, not that the shop is slow.

1
ModelSTEP AP214 or IGES, one file per revision.
2
DrawingPDF with datums, tolerances, threads and finish.
3
QuantityOne prototype or 10,000 parts, both are fine.
4
FinishAnodize, plating, powder coat or as-machined.

Step 3

Pick Material and Finish Before You Lock the Price

Material choice sets machinability, and machinability sets cost. Aluminum 6061-T6 cuts fast and holds ±0.005 mm without drama. It is the default for brackets, housings and fixtures. 7075 is stronger but gummier, so deep pockets need more passes. Stainless 304 work-hardens if the tool rubs; 303 is the free-machining grade and better for shafts and fittings.

Titanium TC4 (Ti-6Al-4V) and Inconel cut slowly and wear tools. Use them when the service temperature or weight target demands it, not as a default. Plastics behave differently again. POM and PEEK hold tolerance well; ABS and PP flex under clamping, so thin walls may need softer workholding and lighter depth of cut.

Finish should be chosen with the drawing open. A hardcoat anodize adds 20-50 μm per surface and can close a tight bore. Bead blasting hides tool marks but blurs a sharp edge. Laser marking needs a minimum character height of 1.5 mm to stay legible after anodizing. If a finish changes a dimension, say so on the drawing.

One practical rule: pick material and finish before you approve the price. Changing from 6061 to 304 after quoting restarts the whole cycle, including the DFM review.

1
Aluminum6061-T6, 7075, 2024, 5052, 6082, ADC12.
2
Stainless303, 304, 316L, 17-4PH, 440C.
3
Steel1018, 1045, 4140, 4340, A36, tool steel.
4
PlasticsPOM, PEEK, PC, PMMA, ABS, PA, carbon fibre.

Step 4 and 5

Tolerances, Datums and the Setup Plan

Tolerance is the single biggest lever on price. A general note of ±0.1 mm lets the shop run standard tooling and normal feeds. A bearing bore at ±0.005 mm needs a finishing pass, a temperature-stable measurement, and often a reamed or bored operation instead of an end mill. Put tight tolerances only where the function needs them.

Datums matter just as much. If your drawing calls datum A on a face that the shop cannot hold in the first setup, the shop has to build a fixture or re-fixture the part. Both add time and stack-up error. A good drawing uses datums that match a realistic first setup: a flat face, a bore, or two edges.

Geometry drives the machine choice. A part with features on five sides belongs on a simultaneous 5-axis center, where one setup reaches all of them. A long shaft with a turned diameter and a milled flat belongs on a mill-turn center. A simple plate with holes belongs on a 3-axis mill. Send the model and let the shop propose the setup; that conversation usually saves more than any price negotiation.

Size limits are worth checking early. Our largest travel is 4,000 × 400 × 150 mm, with 750 × 1,150 × 550 mm and 600 × 600 × 600 mm cells for mid-size parts, and a Ø400 mm rotary table for round work. If a part is bigger than the travel, it has to be split or made another way.

1
General tolerance±0.1 mm on non-critical features.
2
Critical fit±0.005 mm on bores and bearing seats.
3
Surface finishRa 1.6–3.2 μm as-machined, Ra 0.2–0.8 μm fine.
4
Inspection100% before shipment, reports on request.

From drawing to first article

Step by Step: Releasing the Job

Follow this order and the job moves without a second round of questions.

1
Send the model, drawing and quantitySTEP plus PDF drawing, quantity, material and finish. One email is enough. Quote and free DFM analysis come back within 12 hours.
2
Read the DFM note before the priceCheck thin walls, deep pockets, corner radii and tool reach. Reply with accepted or rejected changes. Unanswered DFM notes are the most common cause of a stalled job.
3
Confirm material, finish and tolerance classState the alloy and temper, for example 6061-T6 rather than aluminum. List which features are tight and which are general tolerance.
4
Approve the drawing revision in writingReply with the revision letter you want cut. Once a revision is approved, a later change means a new setup and a new first article.
5
Sign the NDA if the part is sensitiveUploads stay secure and confidential. An NDA is available on request before any file leaves your side.
6
Let production startProduction can start within 24 hours of approval. Parts ship in 3–5 days for typical runs.
7
Measure the first articleCheck the datum features, the tight bores and the finish. Compare against the drawing, not against the model.
8
Release the balance of the batchOnce the first article passes, the remaining pieces run on the same setup and the same program.

Decision guide

Which Setup Fits Your Part

Match the part geometry to the machine before you argue about price.

Part geometry	Recommended setup	Typical tolerance	When it is the wrong choice
Flat plate, holes on one face	3-axis mill	±0.05 mm	Features on the side walls
Housing with features on 4-5 sides	5-axis center, one setup	±0.005 mm on bores	Simple 2-sided plate
Long shaft with a milled flat	Mill-turn center	±0.01 mm	Prismatic block with no turning
Round flange, bolt circle	4-axis mill with Ø400 mm table	±0.02 mm	Square part with corner pockets
Prototype before tooling	3-axis or 5-axis, one piece	±0.05 mm	High-volume casting already tooled
Thin-wall plastic cover	3-axis with soft jaws	±0.1 mm	Titanium or Inconel at this wall
Large frame, 4,000 mm class	Large-travel 3-axis	±0.05 mm	Parts needing 5-sided access