CNC Processing Services San Jose 95131: 7 Checks Before You Order

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  Key takeaways
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  What to Check Against What You Actually Need
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  Tolerance: What a Shop Actually Holds
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  Lead Time: Three Numbers, Not One
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  Order Size and Material Range
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  Certifications and Paperwork That Survive an Audit
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  Capacity: Does the Shop Fit Your Part?
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  Finishing, Marking and the Cost of a Second Vendor
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  Quoting Discipline: What a Real Quote Contains
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  How to Vet a Supplier in 7 Steps

Every supplier page lists a tolerance number. The useful question is narrower: what tolerance does this shop hold on the feature you drew? A general ±0.005 mm capability does not mean every dimension on a five-axis part lands there. Thin walls, deep pockets and long bores drift. Ask which features the shop machines in one setup and which ones get a second op.

Feature count matters more than the headline number. A part with six critical bores and one datum is easier to hold than a part with thirty toleranced faces on four sides. If your drawing has a true position callout on a bolt pattern, say so at quote time. Shops that program five-axis work in a single setup usually hit those patterns without a fixture change, and that is where the tolerance argument is won or lost.

Material moves the answer too. Aluminium 6061 and 7075 cut clean and hold size well. Stainless 316 and 17-4PH work-harden and pull, and titanium TC4 (Ti-6Al-4V) needs slower feeds and more coolant. Inconel is slower again. A shop that quotes the same tolerance for all four has not read your part.

A practical test: send the STEP file and the drawing, then ask for a DFM note. We return a free DFM analysis with the quotation within 12 hours, including any feature that cannot hold the tolerance you called out.

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  Hold the tightest callout where it mattersLoosen cosmetic and non-mating faces to Ra 1.6–3.2 μm and save cycle time.
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  One setup beats threeFewer re-clamps means less stack-up error on hole patterns.
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  Ask about inspection, not just machining100% inspection before shipment is the proof behind the number.

Buyers often compare a single lead-time figure and pick the smaller one. That hides three separate clocks. The first is quotation: how long until you get a price and a DFM note back. The second is production start: how long until the machine is cutting your material. The third is shipping: how long the finished parts spend in transit.

A supplier can be fast on one and slow on another. Quoting in 12 hours is common among good shops. Starting production within 24 hours after you approve the quote is less common, because it needs material in stock and a free spindle. Parts shipping in 3–5 days is a real capability for small and mid-size runs, not for everything.

Ask what happens when the schedule slips. Past performance is the only honest answer, and a shop should be able to tell you its historical late-delivery rate. We track ours below 2%. That number is worth more than a promise, because it is measured rather than stated.

One trap: a low price with a long queue. If the shop is cheap because your job waits behind larger orders, the saving costs you a week. Ask where your job sits in the queue before you sign.

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  Quote clock12 hours for price plus DFM analysis.
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  Production clockStart within 24 hours after approval.
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  Shipping clock3–5 days for typical runs.

Prototype teams in the 95131 area usually start with one to five pieces, then scale. A supplier with a minimum order quantity forces you to buy parts you do not need yet, or to split the work between a prototype shop and a production shop. Splitting means two sets of fixtures, two inspection reports and two chances for a dimension to drift.

We run from a single prototype to 10,000+ part runs on the same floor. That matters less for the price and more for the handoff. The program that cut your first article is the one that runs your production batch, so the process knowledge stays in place.

Material range is the second half of this check. A shop that stocks 6061 and 304 only will subcontract anything exotic, and you lose visibility. Our list covers aluminium 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075 and ADC12; stainless 303, 304, 316, 316L, 420, 430, 431, 440C and 17-4PH; steel 1018, 1045, 4130, 4140, 4340 and A36; copper and brass grades including C36000; titanium TA1, TA2 and TC4; Inconel; magnesium AZ31B and AZ91D; plus plastics such as POM, PEEK, PC and carbon fibre.

Finishing is part of the same question. Anodizing, plating, powder coating, bead blasting and laser marking are common next steps. If the shop cannot do them in house, ask who does and who owns the risk when a batch comes back out of tolerance.

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  No minimum order quantityOne prototype or a 10,000+ run, same process owner.
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  Wide material stockFerrous, non-ferrous, titanium, magnesium and engineering plastics.
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  Finishing under one roofAnodizing, plating, powder coat, blasting, laser marking.

Certificates are not decoration. Each one answers a different question. ISO 9001:2015 says the quality system is documented and audited. IATF 16949:2016 adds automotive-specific process control and traceability, which is what a Tier 1 supplier will ask for before they let you into a program. ISO 13485:2016 is the medical device equivalent. ISO 27001:2022 covers information security, which matters when your CAD files are the product.

Match the certificate to the program, not to the marketing. A general industrial bracket does not need IATF paperwork. A brake component or a battery pack part usually does. A surgical instrument housing needs ISO 13485 and a traceability chain from material lot to finished part.

Ask how inspection is recorded. Raw material check, in-process monitoring and final inspection are three separate gates. Reports are available on request. If a supplier cannot show you a sample inspection report before you order, that is the answer to your question.

Confidentiality belongs here too. Uploads should be secure, and an NDA should be available on request, signed before files move. For hardware teams, the drawing is often the most valuable thing in the room.

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  ISO 9001:2015General manufacturing baseline.
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  IATF 16949:2016Automotive and EV programs.
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  ISO 13485:2016Medical device components.
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  ISO 27001:2022Design file and data security.

Capacity is a geometry question before it is a volume question. A part that fits in a 500 × 500 × 450 mm envelope can be cut on many machines. A 4,000 mm frame cannot. Ask for the working envelope, not the machine count.

Our floor runs 127 high-precision CNC machines, including 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers. Maximum processing size is 4,000 mm, with travel envelopes of 4,000 × 400 × 150 mm, 750 × 1,150 × 550 mm, 600 × 600 × 600 mm, 500 × 500 × 450 mm and 500 × 310 × 200 mm. Rotary tables go up to Ø400 mm.

Why does five-axis matter for a buyer? It removes setups. A part with angled faces, undercuts or a compound hole pattern can be cut in one clamping. Each removed setup removes a source of position error and a queue slot. For complex housings and impellers, that is the difference between holding ±0.005 mm and chasing it.

Mill-turn centers cover parts that need turning and milling without a second machine. Shafts with cross holes, fittings with flats, and small valve bodies fit here. If your part has both a turned diameter and a milled feature, ask whether it can run in one mill-turn cycle.

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  Up to 4,000 mmLarge frames and long extrusions.
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  16 five-axis centersAngled faces and compound holes in one setup.
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  16 mill-turn centersTurned and milled features in one cycle.

A machined part is rarely finished when it leaves the spindle. Surface finish, coating and marking decide how it looks and how it survives. Ra 0.2–0.8 μm is a fine finish for sealing faces and sliding surfaces. Ra 0.8–1.6 μm is the usual high-quality machined look. Ra 1.6–3.2 μm is as-machined and fine for brackets and internal parts.

Specify the finish by function. A sealing face needs a fine finish. A painted cover needs a blast profile for adhesion. A conductive anodize is different from a hardcoat. If you write "anodize" without a type, expect a conversation at inspection.

Marking has a hard limit worth knowing: laser marking has a minimum character height of 1.5 mm. If your part number needs to fit in a 1 mm space, plan for a different marking method or a larger label area.

Sending finishing to a second vendor adds a shipping step, a re-inspection and a schedule you do not control. It also splits responsibility when a coated part comes back out of tolerance. Keeping machining, finishing and inspection with one supplier keeps the chain short.

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  Function firstPick the finish from the contact surface, not the catalog.
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  Marking limitLaser marking minimum character height is 1.5 mm.
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  One chainMachining, finishing and inspection under one roof.

A quote is a technical document. It should name the material and temper, the process, the number of setups, the finish callout and the inspection level. It should also flag any feature that cannot be made as drawn. A price without those items is a placeholder, and it will move.

The fastest way to a usable price is a complete package: STEP or IGES model, a 2D drawing with tolerances and datums, the material and temper, the finish, the quantity and the target date. Missing datum callouts and open tolerance blocks are the two most common reasons a quote gets padded with contingency.

Ask what the price excludes. Tooling, fixtures, first-article inspection and expedited freight are the usual extras. None of them are unfair, but you want them named before the PO, not after.

A shop that sends a DFM note with the price is telling you it read the model. That note is where you learn that a 0.5 mm internal corner needs a smaller tool and more time, or that a deep pocket needs a different approach. We send one with every quotation, at no cost, within 12 hours.

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  Complete package inModel, drawing, material, finish, quantity, date.
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  Exclusions namedTooling, fixtures, first article, expedited freight.
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  DFM note attachedShows the model was read before pricing.