How to Get a CNC Machining Quote That
Doesn't Waste Your Time

Most engineers send a drawing, wait three days, then receive a quote that's 40% over budget and full of clarification questions they could have answered in five minutes. Here's how to fix that — permanently.

Why most quotes take forever (and come back wrong)

When a machining shop receives an incomplete drawing, someone has to stop what they're doing, read the file, identify the gaps, write an email, and wait for your reply before they can price anything. Every back-and-forth adds 12–24 hours. Do that twice and you've lost a week.

The shops that quote fastest aren't necessarily faster at machining — they're faster because customers send them complete information. So let's make you one of those customers.

The 8 things every CNC quote request needs

1. A 3D file AND a 2D drawing

The 3D file (STEP, IGES, or Parasolid) tells the machinist what the geometry is. The 2D drawing tells them what matters — tolerances, surface finishes, thread callouts, and GD&T. Sending only a 3D file means the shop will assume default tolerances (usually ±0.1mm), which may be wrong for your application. Sending only a 2D PDF means they'll spend time reconstructing geometry they could have imported directly.

Send both. Always.

2. Material specified down to the grade and temper

"Aluminium" is not a material spec. "AL6061-T6" is. The difference in machinability, cost, and lead time between AL6061-T6 and AL7075-T651 is significant. If you're not sure which grade you need, say so — a good shop will advise you. But don't leave it blank.

3. Surface finish for every surface that matters

If a surface is unmachined, say so. If it needs Ra 0.8µm, call it out on the drawing with a surface finish symbol — don't write it in an email where it might get missed. If you only care about a few critical surfaces, mark the others "as machined" — this reduces cost significantly.

4. Tolerances on features that matter, not everything

Over-tolerancing is the single biggest way to inflate your quote unnecessarily. If a clearance hole for an M5 screw doesn't need to be ±0.01mm, don't call it out that way. Standard ISO 2768-m covers most non-critical features. Reserve tight callouts for bearing bores, sealing surfaces, and mating interfaces.

5. Surface treatment and finish

Clear anodise, hard anodise, powder coat, electroless nickel — each has different lead times, costs, and DFM implications. If you need a specific colour or gloss level, say so. If you have a Pantone or RAL reference, include it.

6. Quantity (prototype vs. production)

Quoting 1 off vs. 100 off vs. 1,000 off requires completely different approaches — fixturing strategy, toolpaths, and sometimes material sourcing change at different quantities. Give the shop the real number, or at least the range you're planning. "Quote for 5, but we might order 50" is useful information.

7. Required lead time

If you need it in 7 days, say so upfront. Rush jobs can usually be accommodated, but the shop needs to know to schedule it differently. Discovering on day 3 that you needed it yesterday helps no one.

8. The intended use (briefly)

This sounds unnecessary but it's the most underrated piece of context in a quote request. "Heatsink for a 150W GPU — thermal conductivity is the priority" tells a machinist that you might benefit from AL6063 instead of 6061, or copper instead of aluminium. "Structural bracket for a UAV" tells them to flag any features that might be a fatigue risk. One sentence of context can save days of DFM back-and-forth.

What NOT to send

• Screenshots of drawings. Low resolution, no scale, no metadata. Send the actual PDF or DXF.
• STL files as your only 3D reference. STL is a mesh format — it has no dimension data, no tolerances, and is painful to work with in CAM software.
• Drawings with revision history buried in a change log. Make sure the drawing you send is Rev X, not Rev A with handwritten corrections.
• Verbal specs in an email with no drawing. "I need a box, 100×50×30, 3mm wall, aluminium, anodised black" feels complete but produces five clarifying questions every time.

How to structure your email

That email produces one response: a quote. Not five questions, not a request for a different file format — a quote.

One more thing: ask for DFM feedback

Always include "please flag any DFM issues before quoting." A good shop will tell you if a feature is unnecessarily expensive to machine, if a tolerance is tighter than it needs to be, or if a design change would cut lead time in half. This costs you nothing extra and can save you significant time and money on the next revision.

At Quality Prototype, DFM review is included with every quote request, automatically. We'd rather spend 20 minutes flagging a problem now than machine a part that doesn't work.