What is the typical lead time for CNC milled parts?

Prototypes and low-volume orders of CNC machined parts ship in 1 to 10 business days. For production, lead time depends on quantity, material and finishes, and appears with the price on your quote. If you need your parts urgently, let us know when you request your quote.

What tolerances can be achieved with CNC milling?

Standard CNC milling tolerances are typically ±0.005" (ISO 2768-m). For critical features, tighter tolerances down to ±0.001" can be achieved with stable setups, controlled tooling strategies, and appropriate inspection methods. Use our ***interactive ISO 2768 chart***(/resources/charts/iso-2768-tolerance-chart), ***tap drill calculator***(/resources/tools/drill-tap-chart), and ***drill bit size chart***(/resources/charts/drill-bit-size-chart) when specifying holes and threads.

Which materials machine best for CNC milling?

Aluminum 6061-T6 is the most cost-effective and predictable material for CNC milling. For plastics, Acetal (Delrin) offers excellent dimensional stability and surface finish. Harder alloys and filled plastics may increase cycle time and tooling wear.

Can parts be machined from a 3D CAD model without a 2D drawing?

We can CNC mill parts directly from 3D CAD files such as STEP or Parasolid. However, a 2D drawing is strongly recommended when specific tolerances, GD&T callouts, surface finishes, or thread requirements are critical.

What is the maximum part size for CNC milling?

Up to 40" × 20" × 20". If your part is larger or unusual, we review it case by case based on fixturing and setups.

Do you provide inspection reports and material traceability?

Yes. Material certifications (MTRs), Certificates of Conformance (CoC), and dimensional inspection reports are available upon request. Inspection scope can be aligned to project requirements, including first-article validation.

What surface finishes are available for CNC milled parts?

Common finishes include As-Milled (Ra ~125), Bead Blasting, Type II and Type III Anodizing, Conversion Coatings, Electroless Nickel Plating, and Powder Coating. Finish availability depends on material and part geometry.

How can I reduce the cost of CNC milled parts?

Cost can be reduced by increasing internal corner radii, avoiding deep or narrow pockets, limiting tight tolerances to functional features only, and designing parts to minimize setup count and tool changes.

Can you repeat the same milled part on every order?

Yes. CNC milling is well suited to repeating prismatic parts. With stable fixturing, documented setups and an inspection plan, your part comes out the same order after order.

Precision CNC Milling

Custom CNC Milling Services

3-axis CNC milling for anyone who needs a part: students, makers, startups, machine shops, engineers and businesses of any size. Tight tolerances, 1 part or thousands, no minimums.

3-axis CNC milling, tolerances down to ±0.025 mm
Aluminum, steels, stainless, engineering plastics and more
From one part, no minimums

Request a quote Manual quote

Upload your file and quote your milled part

CAD model of a milled aluminum housing with two pockets and mounting holes — Housing · Aluminum 6061

CAD model of a steel bearing support with a stepped bore and slotted base — Support · Steel 1018

CAD model of a Delrin assembly fixture with stepped circular seats — Fixture · Delrin

Upload your 3D filesDrag your files here

STEP, STP, STL, 3MF, DXF, DWG · Drawings as PDF or photo · Start without an account

Confidential files. Your design and intellectual property stay yours.

No CAD file? Request a manual quote

Home/Capabilities/Custom CNC Machining Services/Custom CNC Milling

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Manufacturing services

Precision CNC Milling

Custom CNC Milling Services

3-axis CNC milling for anyone who needs a part: students, makers, startups, machine shops, engineers and businesses of any size. Tight tolerances, 1 part or thousands, no minimums.

3-axis CNC milling, tolerances down to ±0.025 mm
Aluminum, steels, stainless, engineering plastics and more
From one part, no minimums

Request a quote Manual quote

Upload your file and quote your milled part

Upload your 3D filesDrag your files here

STEP, STP, STL, 3MF, DXF, DWG · Drawings as PDF or photo · Start without an account

Confidential files. Your design and intellectual property stay yours.

No CAD file? Request a manual quote

Home/Capabilities/Custom CNC Machining Services/Custom CNC Milling

CNC Milling

Why Choose PREMSA for Custom CNC Milling

At PREMSA we do precision CNC milling for your part: tight tolerances, repeatable geometry and on-time delivery. We machine metals and engineering plastics from your CAD and tell you plainly what can be made, what drives cost and what gets inspected.

Before we cut, an engineer reviews your part: critical features, datums and GD&T, and suggests changes that cut cycle time without hurting how it works. That means fewer revisions, less tolerance stack-up, and a part that's right the first time. Want a head start? Use our ***CNC Machining Guidelines***(/resources/guides/cnc-design-guide) before you quote.

From rapid CNC milling prototypes to production lots, with a documented process, optional material certifications (MTR/CoC) and inspection reports. Your part, accurate and on time, whether it's 1 or a thousand.

What is CNC Milling?

CNC milling is a subtractive manufacturing process that uses rotating cutting tools to remove material from a solid block or plate and create precise 3D features. A CNC mill follows programmed toolpaths to machine pockets, slots, contours, holes, and planar surfaces with controlled tolerances and repeatable results.

Use CNC milling for functional parts that need accuracy, real material properties and a clean finish. It's ideal for prismatic parts, housings, fixtures, brackets, manifolds and multi-face parts machined with well-planned 3-axis setups.

How PREMSA Works

From uploading your CAD to getting your parts—fast and straightforward.

app.premsaindustries.com

Your three milled parts uploaded in the portal, each in 3D with its dimensions

System Status20% Complete

Types of CNC Mills

3-Axis CNC Milling

The most common CNC milling setup for flat and prismatic parts. Best for pockets, slots, hole patterns and planar features. Cost-effective for prototypes and production when features are reachable from standard orientations.

Benefits of CNC Milling

High Accuracy & Repeatability

CNC milling produces consistent parts with predictable tolerances, making it ideal for assemblies, precision interfaces, and repeat production orders.

Production-Grade Materials

Machine real engineering metals and plastics—aluminum, steel, stainless, titanium, acetal, PEEK, and more—maintaining material integrity for end-use applications.

Complex Features in Fewer Setups

Grouping features into fewer 3-axis setups reduces repositioning, improves geometric accuracy, and helps control true position, perpendicularity, and profile tolerances on multi-face parts.

Controlled Surface Finish Options

Achieve functional and cosmetic finishes with specified roughness (Ra), bead blasting, anodizing, plating, and other secondary operations tailored to your application.

Fast Prototyping to Scalable Production

Iterate on prototypes fast and order more when you need it, without the cost and wait of hard tooling.

DFM-Driven Cost Optimization

Practical DFM feedback—like increasing internal radii, reducing deep pockets, and limiting tight tolerances to critical features—can significantly lower cycle time and unit cost.

Capacity Benchmarks

Work Envelope & CNC Milling Capabilities

Maximum Part Size

Work envelope of our 3-axis mill. Suitable for large prismatic parts, multi-face machining and complex fixturing where alignment across faces matters.

40" x 20" x 20"

Minimum Feature Size

Minimum achievable feature size in CNC milling depends on material properties, cutter diameter, tool reach, and part rigidity. Fine features, thin walls, and tight internal radii are evaluated through DFM to ensure machining stability and repeatability.

±0.001" / 0.005" Rad

Batch Sizes & Volumes

From a single-part prototype to repeat orders. Documentation and inspection scale with quantity so quality stays the same.

Prototype to production

Exceeding these limits?

Part isn't standard? Upload your CAD and an engineer will review your milling job.

CNC Milling Tolerances & GD&T

CNC milling tolerances and GD&T definitions directly influence machining strategy, setup planning, and inspection methods. Clearly identifying critical features enables proper tool selection, datum alignment, and repeatable results across milling operations.

Category	Technical Description	Typical Notes
Standard CNC Milling Tolerances	Standard tolerances commonly achieved in CNC milling without special environmental control or custom fixturing. Typical defaults include ±0.005" or ISO 2768-m for prismatic, multi-face milled components.	Apply standard tolerances wherever possible to reduce setup complexity and machining time.
Tight & Precision Milling Tolerances	Tolerances down to ±0.001" are achievable with stable datums, rigid workholding, controlled cutting forces, and optimized finishing strategies during CNC milling.	Restrict tight tolerances to functional features to control cost and inspection effort.
Threads & Tapped Holes	Threaded features produced via CNC milling and tapping in accordance with ASME (UNC/UNF) or ISO metric standards. Thread depth and class selection impact tool life and cycle time.	Specify thread standard, class, depth, and preferred method (thread milling or tapping).
Surface Finish (Ra)	Surface roughness in CNC milling is controlled by cutter geometry, step-over, spindle speed, and finishing passes. Typical as-milled surfaces range from Ra 125 to Ra 32, with finer finishes achievable on accessible features.	Call out Ra only on functional or cosmetic surfaces to avoid unnecessary finishing operations.
Inspection & GD&T Verification	Verification of milled features and GD&T characteristics such as flatness, perpendicularity, true position, and profile using calibrated precision metrology equipment.	Define inspection scope early (spot check, full inspection, or FAI) to align expectations on cost and lead time.

Standard Reference: ISO 2768-m (Medium) unless otherwise specified

CNC Milling Materials

We machine a wide selection of metals and engineering plastics. Don’t see your material? Upload your spec and we'll confirm availability and machinability within 24 hours.

CNC Milling Metals

CNC Machining Plastics

Surface Finishes

Pick a finish for corrosion resistance, wear protection, electrical conductivity or just looks. Need a special specification? Upload your print or finishing spec and we'll confirm if it can be done and when.

CNC Milling Finishing Options

CNC Milling Design Guidelines (DFM) (DFM)

Designing parts specifically for CNC milling improves manufacturability, shortens lead times, and reduces cost per part. These CNC milling DFM guidelines address tool accessibility, feature stability, and tolerance control to ensure predictable results across 3-axis milling operations.

Design Feature	Technical Recommendation
Internal Corner Radii & End Mill Access	Internal corners should be designed to accommodate standard end mill diameters. Sharp internal corners increase tool deflection and machining time. As a guideline, use internal radii equal to or greater than 10–15% of pocket depth to improve surface finish and dimensional consistency.
Minimum Wall Thickness for CNC Milling	Thin walls are susceptible to vibration and deflection during milling. Maintain minimum wall thicknesses of approximately 0.020" (0.5 mm) for metals and 0.040" (1.0 mm) for plastics to preserve dimensional accuracy and surface integrity.
Hole Depth Ratios & Thread Engagement	For drilled features, limit depth-to-diameter ratios to 8–10× to maintain straightness and tool life. Threaded features typically require 1.5–2× diameter engagement; deeper threads add cost and risk without improving mechanical performance.
Undercuts, Side Features & Tool Reach	Undercuts and side features requiring specialty cutters should be avoided unless functionally necessary. Features that can be machined in a single CNC milling setup reduce fixturing complexity and improve positional accuracy.
Setup Strategy & Machining Complexity	Parts designed for standard 3-axis milling orientations reduce re-clamping and tolerance stack-up. Minimizing setup count is one of the most effective ways to lower CNC milling costs and improve repeatability.
2D Drawings, GD&T & Inspection Requirements	Define functional datums, GD&T callouts, thread specs and surface roughness (Ra) only where needed. A clear, complete drawing speeds up your milling job and first-article inspection when required.

Applications & Industries

CNC Milling Applications

Structural Machined Components

CNC milled plates, brackets, frames, and load-bearing components where flatness, parallelism, and positional accuracy across multiple faces are critical.

Multi-Face Precision Hardware

Prismatic parts requiring accurate feature-to-feature relationships across multiple setups, driven by datum-based milling strategies.

Assembly-Ready Machined Parts

Finished CNC milled components delivered to final tolerance and surface finish, ready for direct mechanical assembly without secondary operations.

CNC Milling Target Industries

Industrial Equipment & Machinery

CNC milled housings, machine frames, mounting plates, and wear components used in production equipment and heavy industrial systems.

Semiconductor & Electronics Manufacturing

Precision CNC milled fixtures, plates, and enclosures requiring tight flatness, thermal stability, and clean surface finishes for electronic assemblies.

Energy & Power Systems

CNC milled components for power generation, energy storage, and fluid handling systems where strength, alignment, and durability are essential.

FAQs & Knowledge Base

CNC Milling FAQs

Custom CNC milling services

CNC milling is the right process when your part has flats, pockets, slots, bosses or contoured surfaces that a lathe can't make efficiently. At PREMSA we 3-axis mill prismatic parts, pockets and multi-face components with as few setups as possible.

Pair this service with our CNC turning and mill-turn pages when your assembly mixes milled and turned features, and use the CNC design guide to reduce DFM iterations before you quote. CNC milling is part of our industrial machining in Mexico.

PREMSA ecosystem

Services, guides, and tools for CNC milling

We make your part in Monterrey and ship it across Mexico and abroad. We do 3-axis milling for prismatic parts and complex cavities with ISO 2768 tolerances and engineering materials, from 1 prototype to production. Use the technical references below and quote online with STEP or STL files.

CNC processes

Engineering tools