What is VMC job work?

Machining parts on a workshop's vertical machining centre to your drawing: milling, drilling, tapping and boring, paid per piece or per machine hour.

What tolerance can VMC milling hold?

About ±0.01–0.02 mm is normal; closer limits are possible on selected features with care, or by grinding afterwards.

Why do I need to send a STEP file?

Workshops program the machine from the 3D model; with only a PDF they must model the part first, which costs time and can introduce errors.

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VMC / CNC milling

Also called: VMC job work, CNC milling job work, VMC machining, CNC milling services, machined parts

VMC (CNC milling) job work machines flat and box-shaped parts on a vertical machining centre: faces, pockets, slots, profiles and hole patterns, typically to ±0.01–0.02 mm. It is the usual way to make plates, brackets, housings, fixtures and mould parts.

Quick facts

Machines: VMC, HMC, 5-axis machining centre
Typical tolerance: ±0.01–0.02 mm
Typical surface finish: Ra 0.8–3.2 µm
Quantities: One-offs to batches of thousands
Usually priced: Per piece, or per machine hour for one-offs
Best input: 3D model (STEP) plus drawing

How it works

The part is clamped in a vice or fixture on the machine table. Rotating cutters (end mills, face mills, drills, taps) remove material along paths programmed from the 3D model, with the tool changer swapping tools automatically. Parts with features on several faces are turned over between setups, or machined on a 4th axis or an HMC.

Typical parts

Plates, brackets and blocks
Housings, covers and manifolds
Jigs, fixtures and automation parts
Mould and die parts
Flanges and parts with hole patterns

What decides the price

Material and the size of the block it starts from
Machining time: how much material comes off, and how many tools
Number of setups (each face that needs turning over adds cost)
Tight tolerances, fine finishes and deep pockets slow the cutting
Quantity: programming and fixtures are shared over the batch
Extras: anodising, plating, heat treatment, inspection reports

Design tips that save money

Give inside corners a radius a little larger than the cutter (sharp inside corners need EDM)
Keep pockets no deeper than about 3–4 times the cutter diameter where possible
Use standard hole sizes and thread sizes
Avoid very thin walls, which vibrate and bend
Put tight tolerances only where parts fit together
Design so most features can be reached from one or two sides

What to send a workshop

3D model (STEP) and a drawing (PDF) with tolerances
Material grade
Quantity and how often you will reorder
Surface treatment needed (anodising, plating, painting)
Inspection needs and delivery date

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Related job work

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Materials

Questions

What is VMC job work?: Machining parts on a workshop's vertical machining centre to your drawing: milling, drilling, tapping and boring, paid per piece or per machine hour.
What tolerance can VMC milling hold?: About ±0.01–0.02 mm is normal; closer limits are possible on selected features with care, or by grinding afterwards.
Why do I need to send a STEP file?: Workshops program the machine from the 3D model; with only a PDF they must model the part first, which costs time and can introduce errors.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 8 October 2026.