Wood CNC Processing Services Bristol: A Buyer's Checklist

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  Key takeaways
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  What to compare before you send a PO
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  Tolerance: why wood and metal need separate numbers
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  Material and grain: what actually drives your price
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  Machine setup and toolpath strategy
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  Lead time, MOQ, and how quotes are written
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  Finishing and assembly after the cut
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  Documentation, certification, and confidentiality
• 9
  Where wood CNC is the wrong choice
• 10
  Step by step: qualifying a wood CNC supplier

Wood is a hygroscopic material. An oak panel machined at 20 °C and 50% relative humidity will grow 0.2–0.4% across the grain when the same shop floor sits at 70% humidity a week later. That is 1 mm on a 300 mm width. No machine can hold ±0.005 mm on a material that moves that much after the cut. Buyers who ask for metal tolerance on a wooden part are buying a rejection.

The practical band for machined wood on a router is ±0.1–0.2 mm on a part that is at equilibrium moisture content, measured immediately after cutting. Tighten that only where a hardwood insert, a metal sleeve, or a bearing seat sits. For those features, machine the wood pocket 0.1 mm undersize and finish the metal insert to ±0.005 mm on a mill. Mixing materials in one assembly is normal. Mixing tolerances is the mistake.

If your drawing shows a single blanket tolerance in the title block, expect a shop to quote either too high or too loose. Split the drawing into wood features and metal features before you ask for a price.

The same 3D model can cost twice as much in solid ash as in MDF. Grain direction is the reason. A cutter moving along the grain shears fibers cleanly. A cutter moving across the grain lifts them and leaves fuzz that needs a second pass at a lower feed. Parts drawn with a shallow angle to the grain are the worst case: the tool is always partly climbing and partly cutting down.

Density matters too. A softwood like pine cuts fast but crushes at the clamp point. Hard maple and oak hold a thread and a sharp edge, so they suit jigs, fixtures, and tooling boards. Plywood and MDF machine flat and stable, which makes them the normal choice for painted panels and vacuum fixtures. Tell the shop what the part does, not just what it is made of.

Sheet goods also change the layout math. A part that nests cleanly in a 1,220 × 2,440 mm sheet wastes less material, and material waste is often 30–50% of the quoted price on a wood job. Rotating a part 15° in the nest can pay for itself.

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  Along the grainCleanest shear, fewest finish passes, lowest cost.
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  Across the grainFiber lift and fuzz; budget a second pass.
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  MDF and plywoodStable and flat, but no grain to hide a scratch.
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  Hard maple and oakBest for jigs and fixtures that take abuse.

Ask what machine runs the job and how many axes are simultaneous. A three-axis router cuts the top face and needs a flip for the back. Every flip introduces a datum shift, and on a 600 mm part a 0.15 mm shift is realistic. A five-axis machine can reach an undercut and a side wall in one setup, which removes that shift. We run 16 simultaneous five-axis centers, 12 four-axis mills, and 27 three-axis machines, with a maximum processing size of 4,000 mm.

The toolpath strategy decides your surface finish more than the spindle does. A 12 mm flat end mill roughs fast but leaves scallops. A 6 mm ball nose with a 0.3–0.5 mm stepover gives a finish that needs little sanding. Stepover above 1 mm leaves visible ridges on a curved surface, and no amount of hand sanding fixes a ridge without changing the shape.

For deep pockets, watch the tool length. A cutter sticking out 80 mm deflects. Keep the length-to-diameter ratio under 4:1 where you can, and open the corner radius so the tool can clear chips. Wood dust packs a narrow slot faster than metal chips do.

Split the lead time into three numbers: quote turnaround, production start, and shipping. A vague '4 to 6 weeks' hides which step is slow. Our numbers are a quotation and free DFM analysis within 12 hours, production starting within 24 hours, and parts shipping in 3–5 days. Those are separate commitments, so you can see where a delay lands.

MOQ is the check that rules out most workshops for a design that is still moving. If a shop needs 500 pieces to set up, you cannot test a joint detail in the real material. We take one prototype to runs of 10,000+ parts. For a first article, that difference is the whole point of the exercise.

Read the quote line by line. A price without a stated finish, a material grade, and an inspection level is not comparable to another price. Ask for the material specification by grade, the finish by Ra band, and the inspection list in writing. Two quotes that look 20% apart usually differ in one of those three.

Machining leaves a surface that is ready for some processes and not others. As-machined wood at Ra 1.6–3.2 μm takes glue and paint well after light sanding. If the part is a visible panel, the finish step is where the money goes, so decide early whether the shop or your own team does it.

Wood parts often ship with metal hardware pressed in. That means the shop has to hold the wood pocket and the metal insert to different bands and check the press fit. Doing both in one shop avoids the classic failure where a bushing arrives 0.05 mm oversized and splits the surrounding grain on assembly.

For metal components in the same assembly, we run anodizing, electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, and laser marking with a minimum character height of 1.5 mm. On wood, the equivalent choices are sanding grit, sealer, and topcoat. Name the grit and the sheen, not just 'smooth' or 'natural'.

For a wood part that goes into a machine or a building, traceability matters as much as the cut. Ask which inspection steps run on your order: raw material check, in-process monitoring, and final inspection before shipment. Reports should be available on request, not as an extra you have to negotiate after a problem appears.

Certification is a filter, not a score. ISO 9001:2015 covers quality management. IATF 16949:2016 applies to automotive work. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security. Match the certificate to the industry your part serves. A wood fixture for an assembly line does not need a medical certificate, and a medical device housing does.

Send drawings under NDA if the design is sensitive. Uploads are handled as secure and confidential, and a non-disclosure agreement is available on request. Get that in place before the first file transfer, not after.

Not every part should be routed from wood. If the part needs a wear surface that sees constant sliding contact, wood will polish and then crush. Use a metal or plastic insert. If the part must hold a thread under load, a tapped hole in end grain will strip. Design a metal insert or a through-bolt instead.

Very thin wooden webs are another trap. Below about 3 mm, cutter deflection and grain run-out dominate, and the wall thickness will vary more than the tolerance you asked for. Thicken the web or switch to a composite. Parts with deep, narrow slots have the same problem: the tool cannot clear chips and the slot burns.

Finally, if the quantity is high and the shape is simple and flat, wood CNC may lose to a press or a molder on unit cost. Routing wins on complex geometry, short runs, and designs that change. Pick the process that matches the geometry, not the one you already have a quote for.