CNC machining creates geometry. Sanding, sealing, painting, hardware installation, assembly and retail packing are separate stages unless they are expressly included in the quotation. They can also change the geometry that should be machined.
Write the intended production sequence before finalising the design. A pocket that is easy to cut may be impossible to sand evenly. A slot that fits in raw MDF may bind after primer and paint. A screw recess can be dimensionally correct but inaccessible to the installation tool.
Define the hand-off state
Avoid using “blank”, “finished part” or “CNC cut” as the whole specification. State the actual condition expected when responsibility changes hands:
- machined sheet with parts still retained;
- separated raw components;
- agreed edge preparation;
- sanded blanks;
- coated parts;
- assembled components;
- grouped transit packing.
Quotes define exactly what is included. Depending on the project, this may cover CNC machining only or additional agreed stages such as part separation, preparation or packing. Assembly, finishing and other post-machining work are included only when expressly stated in the quotation.
For seller products, distinguish transit protection from retail packaging and fulfilment. A quotation for machined blanks does not imply stockholding, customer dispatch or marketplace-ready packing.
Map the finishing sequence
Three broad routes are common:
- Machine, assemble, then finish the complete item.
- Machine and finish separate parts, then assemble.
- Supply machined blanks for the customer or seller to prepare and finish.
Each changes access, fit, marking and handling. If parts are coated separately, mating surfaces may need clearance and glue areas may need masking. If assembly happens first, internal corners and recesses must remain reachable. If another party finishes the blanks, the expected raw edge and surface condition must be described accurately.
Visible faces and edges
Mark which face and edges remain visible. MDF factory faces and routed edges respond differently to preparation. Plywood edges expose layers and can reveal natural or manufacturing variation. Its faces and grain direction may affect appearance across a set.
Useful drawing notes include:
- Face A is the finished front.
- Face B contains hardware recesses.
- Grain direction is mandatory, preferred or unrestricted.
- These two edges remain visible.
- These edges form a critical fit and must not receive unplanned cleanup.
- Temporary labels must not leave residue on the coating surface.
Without these notes, efficient nesting or handling may produce the correct outline on the wrong face.
Design for sanding and coating access
Deep narrow pockets, closely spaced raised areas and sharp internal details can be difficult to prepare. Coating may pool inside corners or bridge fine engraving. Dust is harder to remove from small recesses.
Review:
- whether fingers, abrasives or application tools can reach each surface;
- whether internal radii are consistent and practical to prepare;
- whether fine engraving survives primer and paint;
- whether a pocket floor needs the same finish as the face;
- whether a fragile edge will hold the intended coating;
- where the part can be held while coating and curing.
If finish quality drives the product, test the complete finish system on representative machined material rather than relying on a generic sample chip.
Finish changes dimensions
Primer, paint, lacquer, veneer, adhesive and edge treatment can add material or change friction. The effect may be negligible on a decorative outline but decisive in a removable slot, hardware recess or flush stack.
Do not subtract a guessed coating allowance from the drawing and assume the relationship is controlled. Define the finished behaviour, apply the real process to a representative coupon and record the approved result. Finish can build unevenly at edges and inside corners.
The joints and tolerance guide explains how material and coating contribute to a fit.
Design around the exact hardware
Hardware descriptions are often nominal. Products with the same general name can have different bodies, flanges, screw positions and installation guidance. Use the actual component or a current manufacturer drawing and exact product reference where practical.
For each hardware feature, identify:
- component and purpose;
- clearance hole, pilot, recess, counterbore or locating feature;
- diameter, depth and reference face;
- installation direction;
- required tool access;
- adjustment or removability;
- finish or adhesive in the stack;
- material remaining around and beneath it.
CNC routing can locate or create a suitable feature, but it is not automatically the final process for every small or precision hole.
Holes, recesses and inserts
A clearance hole lets a fastener or shaft pass. A pilot supports a later operation. A locating hole controls position. A recess allows a head, flange or fitting to sit lower. These purposes need different geometry and acceptance.
Threaded inserts and similar fittings create installation forces and edge-distance requirements. Follow the component supplier’s guidance and test in representative material. Machining a suitable-looking recess does not validate pull-out strength.
If hardware may be substituted, decide whether that change requires a new drawing revision and test. A visually similar item should not inherit approval merely because it enters the same nominal hole.
Edge distance and remaining material
Holes and recesses close to an edge can leave a thin wall or cause breakout. The suitable arrangement depends on material, feature size, hardware, load and installation. Plywood ply structure and MDF edge behaviour differ.
Highlight edge-near features individually. Where load matters, provide design evidence appropriate to the finished application. Moving the feature, thickening the part or using a separate bracket may be more robust than preserving an unsafe layout.
Installation and assembly access
Hardware can fit on the drawing yet be impossible to tighten because a screwdriver, hex key or spanner cannot reach it. Show the assembly direction and approximate tool envelope. Check that later panels do not block access and that the sequence does not trap a component.
For flat-pack items, consider how a first-time assembler identifies faces, parts and hardware. Stable part IDs and unambiguous instructions may matter as much as hole position.
Map the sequence:
- Which part establishes the datum?
- Which joints engage first?
- When is hardware installed?
- Which tool needs access?
- Can a wrong orientation be corrected?
- Does finish need protection during assembly?
A full prototype may be justified when several steps interact.
Finish example: a painted sign blank
A painted sign blank includes a hanging recess and shallow alignment marks. The design needs to identify the finished front, hardware face, actual hanging component, recess depth, sanding route and whether the marks remain visible after primer.
If the seller receives raw blanks, the quotation can define the machined condition while the seller’s tested process covers sealing, paint and retail packing. If any preparation or packing stage is requested from Wood to Spec, it should appear expressly in the reviewed scope rather than being inferred from the word “blank”.
Finish example: a fitted insert
An insert must sit flush after coating. Relevant dimensions include the hardware flange, pocket depth, base material remaining, coating on the pocket rim and any adhesive. A bare trial at nominal depth cannot prove the finished result.
A representative coupon or partial prototype can compare pocket depth and installation method using the actual insert and finish route. The selected result should be tied to the part revision and hardware reference.
Product and packing interaction
Finish needs time and conditions appropriate to the product before surfaces contact packaging. Two coated faces can mark or block if packed too early. Hardware may protrude into protective material or increase packed thickness.
Design and packing should therefore be reviewed together for seller products. Measure a closed physical pack when shipping dimensions matter. Do not assume a material stack calculation includes finish, protection and closure tolerances.
Frequent omissions
- Finishing responsibility is not stated.
- A bare fit is approved for a coated assembly.
- Deep pockets cannot be prepared consistently.
- Fine lettering fills with paint.
- A plywood edge characteristic is treated as a machining defect.
- A hardware recess is based only on a nominal name.
- The installation tool cannot reach the fixing.
- Temporary labels damage the visible face.
- Parts are grouped as retail-ready without retail packing being in scope.
- A successful insert test is mistaken for proof of load capacity.
Information to include in the project review
Provide the desired hand-off state, finish system or target appearance, visible faces, critical fits, actual hardware and assembly sequence. Include manufacturer information for components, photographs of relevant samples and responsibility for preparation, coating, assembly and packing.
Machining guidance does not certify coating suitability, emissions, food contact, toy safety, fire behaviour, wall mounting or structural performance. Follow current material and component guidance and obtain specialist evidence for consequential uses.
Discuss the required hand-off, or compare the standard material options before fixing the finish route.