Texas CNC Processing Service Guide

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  What matters most when you buy machining
• 2
  Which supply route fits your part
• 3
  Tolerance, finish and the size they apply to
• 4
  Lead time, quoted in two parts
• 5
  MOQ, unit cost and how the first run scales
• 6
  Certifications and inspection paperwork
• 7
  What a good quote actually contains
• 8
  Distance, shipping and working with an overseas shop
• 9
  Step by step: qualifying a supplier in one week

A tolerance is only meaningful next to a dimension. A shop that states ±0.005 mm on a 20 mm bracket is describing a different job than one holding ±0.005 mm across a 900 mm plate. Thermal growth, fixture stiffness and tool wear all scale with part size. When you read a capability page, look for a number and a range together.

Surface finish follows the same rule. Ra 1.6–3.2 μm is normal as-machined output on aluminum and mild steel. Ra 0.8–1.6 μm usually needs a finishing pass, a different insert or a slower feed. Ra 0.2–0.8 μm means a secondary operation or a dedicated finishing cell. If a quote lists a fine finish without extra cost or time, ask which operation produces it.

The practical test is to send a drawing with three marked critical dimensions and one finish callout. A serious supplier returns the drawing with the critical features confirmed, and often with a note that one of them needs a fixture change. That note is worth more than a lower price.

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  Send a marked-up drawingMark what is truly critical. Tolerancing everything at ±0.005 mm raises cost for no benefit.
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  Ask for the machineWhich center holds the tolerance, and what travel does it have?
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  Separate cosmetic from functionalVisible faces and sealing faces need different finish specs.

Buyers get burned by a single lead-time number. Split it. The first clock covers quotation, DFM feedback and any drawing questions. The second covers material purchase, machining, finishing, inspection and shipping. A supplier can be fast on the second and slow on the first, and your project still slips.

Ask what happens between the RFQ and the first chip. A useful benchmark is quotation and free DFM analysis within 12 hours, production start within 24 hours once the order is confirmed, and parts shipping in 3–5 days for straightforward jobs. Those figures assume the drawing is released and the material is in stock or standard.

Then ask about the tail. Finishing, plating and heat treatment are outside the machine shop and often the real source of delay. If a part needs anodizing plus laser marking, those steps add days that the machining lead time does not cover. Get the finishing step named in the quote, not folded into a single number.

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  Quote clock vs. production clockAsk for both, in writing.
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  Name the finishing stepPlating and coating have their own queue.
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  Ask about the late-delivery historyA stated late probability below 2% is a trackable claim, not a promise.

Minimum order quantity decides whether you can test a supplier before committing. No minimum order quantity means you can order one prototype and still see the same process, the same inspection routine and the same paperwork you would get on a production run. That is the point of a prototype: it should predict the production part.

Unit cost behaves non-linearly. The first part carries programming, fixturing and setup. The tenth part carries material and cycle time. The thousandth part carries material, cycle time and a small share of setup. If a quote shows a flat per-piece price from 10 to 10,000 pieces, one of those two numbers is wrong.

For metal parts, material choice moves cost more than most buyers expect. A 7075 aluminum housing costs more than 6061 and is harder to finish evenly. Switching from 304 to 316 stainless adds cost and can change the tooling strategy. Ask whether the alloy you specified is required, or whether a standard grade would pass the same test.

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  One prototype, same processThe prototype should be made the way the production part will be made.
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  Watch flat pricingSetup has to be recovered somewhere.
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  Question exotic alloysInconel and titanium are justified by service conditions, not by preference.

Certifications are scoped. ISO 9001:2015 covers a general quality management system. IATF 16949:2016 applies to automotive production. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security, which matters when your drawings and CAD files leave your network.

Inspection is separate from certification. Ask what is measured, how often, and what you receive. A workable standard is raw material verification on receipt, in-process monitoring at defined intervals, and 100% inspection before shipment, with reports available on request. For a first article, ask for dimensional data on the critical features, not a generic pass stamp.

For medical or automotive work, the paperwork is part of the deliverable. Traceability of material lot, a first-article inspection report and a certificate of conformance are usually required by your own quality system. Confirm they are included before the order, because producing them later is much harder.

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  Match the certificate to the productAn automotive certificate is not automatically relevant to a robot arm.
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  Ask for a sample reportSee the format before you need it for an audit.
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  Confirm data securityAn NDA and secure upload handling protect your design.

A quote is a technical document, not just a price. It should state the process route, the machine class, the material grade and condition, the finish, the inspection level and the assumptions it was built on. Assumptions are the useful part. If the quote says the price holds provided the wall stays above 1.5 mm, you know where the risk sits.

Read the DFM notes first. A supplier that flags a deep pocket with a 4:1 depth-to-diameter ratio, or a thread that runs into a radius, is telling you the design will need a change. Finding that before cutting metal saves a week. Finding it after the first article arrives costs the same week plus material.

Be careful with quotes that arrive in an hour with no notes and no questions. Either the part is genuinely simple, or the price was built without reading the drawing. The second case usually surfaces as a revision request after the order is placed.

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  Process route statedWhich operations, in which order.
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  Assumptions listedWall thickness, stock size, tolerances held.
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  DFM notes attachedFree analysis up front beats a change order later.

Texas has a deep machining base, and local suppliers are the right answer when a part is heavy, urgent or needs a face-to-face review. For parts that are small, well specified and repeatable, an overseas partner can be the better fit on cost and on access to five-axis capacity. The question is which one your project actually needs.

The friction in overseas work is rarely the machining. It is communication timing, shipping paperwork and the cost of a mistake that has to travel back. Reduce it by locking the drawing before the order, asking for photos of the first article, and keeping one engineer as the single point of contact on your side.

Confidentiality is a practical concern, not a legal formality. Uploads should be handled as confidential, and a non-disclosure agreement should be available before you send CAD. If a supplier hesitates on an NDA for a new design, that tells you something about how the rest of the project will go.

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  Local for heavy and urgentFreight and review time dominate on large parts.
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  Overseas for repeatable volumeCost and five-axis capacity are the usual reasons.
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  One contact per sideDesign changes get lost in group threads.