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The drawing checklist: what turns a quote into a part that fits
Most wrong parts were not made wrong. They were ordered with a drawing that left the important things to be guessed.
Project
Most wrong parts were not made wrong. They were ordered with a drawing that left the important things to be guessed.
Every job that goes wrong has a moment where somebody assumed something. Usually it is the fabricator assuming a default, and the default being different from what the customer pictured. A drawing checklist is cheaper than that conversation.
| Item | Why it matters | Common default if omitted |
|---|---|---|
| Outline dimensions | Defines the part | No default: the part cannot be made |
| Material and grade | Cast, extruded, ESD, FR, UV, optical | Whatever is on the shelf |
| Thickness and tolerance | Drives stiffness, cost and fit | Nominal, ±10 percent |
| Hole positions and diameters | Defines the fit | Scaled from the drawing, sometimes wrongly |
| Which holes are locating features | Decides process and tolerance | Treated as clearance holes |
| Edge finish, by edge | The most visible and most costly variable | As cut |
| Face finish and which faces are seen | Decides polishing and protection | All faces equal |
| Print, etch or engrave artwork | Defines the graphic and the method | None |
| Fixing detail | Decides whether the part cracks in service | Tight holes, no washers |
| Tolerance for anything that mates | Prevents a part that almost fits | General tolerance only |
| Quantity and inspection level | Decides price and schedule | One off, no inspection report |
A drawing with no visible-face callout gets a part machined and finished symmetrically, which is the most expensive way to make it. Mark the visible faces. Every hole in a visible face costs extra because it has to be re-polished; every hidden edge can be left as cut.
Nobody puts the cleaning product on a drawing, and it is the single fact that most often decides whether a part survives its first year. Ammonia based glass cleaner will craze acrylic; so will acetone, MEK and most workshop degreasers. If the part will be cleaned daily, name the product.
Temperature decides the fixing detail as much as the material. A panel that swings 30 degrees needs slotted holes; one that sits in a stable office does not. It takes one line to state and it prevents the most common service failure.
GENERAL TOLERANCE: ±0.5 mm UNLESS STATED covers most acrylic parts and costs nothing extra.HOLE POSITION: ±0.2 mm only for holes that take a pin, a dowel or a bearing.±0.1 mm on a part under 300 mm is achievable; on a 1,500 mm panel it is not, because the sheet expands more than that over a few degrees.THICKNESS: cast sheet, ±10 percent is normal. ±5 percent selected costs more and is worth it only for a stack that must close.A tolerance is a cost instruction as much as a quality instruction. A general tolerance is free because the process naturally holds it. A tight one means slower feeds, more measurement and a higher reject rate, which is why the price moves when the number gets smaller.
This is the part of the drawing that most affects whether a part lasts, and it is usually the least detailed. A standard block that can be copied onto any acrylic drawing:
FIXING: Ø[fastener + 1.5 to 2 mm] THRU, NYLON WASHER BOTH FACESSLOT ±3 mm ON THE LONG AXIS FOR ANY PANEL OVER 800 mmNO THREAD IN ACRYLIC (or specify an insert and its depth)MIN EDGE DISTANCE 1.5 × HOLE Ø, 2 × WHERE LOADEDDO NOT CLAMP: PANEL TO FLOAT ON GASKETWith that package, a quote is accurate and a first article usually fits. Without it, the quote is a guess and the first article is the test.
We check the drawing against itself first: outline against hole pattern, thickness against the fixing depth, edge distances, radius against cutter. Anything that contradicts is raised with a marked-up drawing before material is cut. That check is free and it is the cheapest part of the whole process.
For a simple flat part, yes, if the dimensions are complete and the material and finish are stated. For anything machined or bonded, a drawn file is faster and avoids a wrong interpretation.
DXF and DWG for flat parts, STEP and IGES for three-dimensional parts, PDF for drawings with notes, and AI, EPS or PDF for print artwork with fonts outlined.
A DXF with hole centres is enough and is less error-prone than a dimensioned drawing. If you send a drawing only, dimension from two datums rather than chaining dimensions, which accumulates error.
It is the tolerance that applies to any dimension without its own callout. We apply ±0.5 mm unless the drawing states otherwise, and we write it on the drawing so both sides have agreed it.
Because it changes the process and the price. A visible face needs protection, careful handling and re-polishing after machining; a hidden face does not. Knowing which is which is how a part gets finished properly at the lowest cost.
Most back-and-forth on a quotation comes from the same eight or nine fields being missing, and the fastest way to stop it is to put those fields on the drawing itself, in a block, filled in. The template below is the one we reconstruct by hand on half the drawings that arrive. Print it, fill it, and the first reply becomes a price instead of a list of questions.
| Field | What to write | What it prevents |
|---|---|---|
| Material and grade | Cast PMMA, 8 mm, clear, one or two sides masked | Extruded sheet substituted on a machined part |
| General tolerance | ±0.3 mm unless noted | Quoting to ±0.1 mm across the whole part |
| Critical features | Datum A = face; holes at ±0.1 mm from A | Tightening every dimension to protect two |
| Edge finish | Diamond polish on visible edges only, as-routed elsewhere | Polishing a metre of hidden edge |
| Bonding | Solvent bond, joints on the returns, cleats hidden | A visible seam under store lighting |
| Annealing | Anneal after machining, 80 °C / 4 h, ramp ≤10 °C/h | Crazing three weeks after delivery |
| Flatness | <1 mm per metre, measured free-standing on three points | Two different measurement methods in one argument |
| Quantity and breaks | 50 / 200 / 500 with a per-store split | A quote that cannot be compared to another quote |
| Packing and marks | Export carton, logo on film, buyer part number label | Re-packing at your warehouse |
The two fields that get skipped most often are edge finish and packing, and they are the two that move the price furthest. On a typical display part, changing "polish everything" to "polish visible edges" removes 30–40% of the finishing cost without changing what the customer sees. Changing from bulk to retail-ready packing can add 8–15% of the goods value. Neither is visible on a drawing that does not mention them, so both get guessed — and the guess is not always the one you wanted.
One habit worth adopting: put the revision number and the date in the file name as well as the title block. We receive files called "bracket-final.dxf" at revision 3, 4 and 5, and the one thing nobody can answer later is which one was approved. A filename of "MJ-2401-bracket-R03-2026-03-14.dxf" costs nothing and settles the question permanently.
We mark up anything that contradicts itself or will not survive service, before material is cut.