The short answer
Good DFM for milled parts is simple: fewer setups, stiffer tools, easier workholding, and only as much tolerance as function requires.
Start with setup count
Every extra face and re-clamp adds time and stack-up risk. Design parts so the critical features can be reached in one or two stable setups. If a feature only exists because 'that is how we modeled it,' remove it before it hits the quote.
A part with perfect CAD symmetry can still be a workholding mess. DFM starts with how the part sits on a machine, not how pretty it looks on screen.
Respect tool access
Inside corners need radii. Deep narrow pockets drive long tools, chatter, slow finishing, and ugly quotes. If you need a sharp inside corner, ask whether EDM or a relief feature is the smarter answer.
Wall height relative to thickness matters. Long unsupported walls move. So do thin floors. You can often save cost by thickening one region by 0.030 to 0.060 in instead of asking the shop to baby the toolpath.
Put precision where it matters
Do not blanket the whole print with tight tolerances. Tie tolerances to assembly function, sealing, bearing fits, and true datums. Leave the rest on general tolerances.
The same logic applies to finish. A sealing face may need a fine Ra. The outside of a hidden housing usually does not.
DFM review points worth checking
Check minimum corner radii, standard hole sizes, thread depth, reachable chamfers, stock size availability, and whether part orientation creates a nasty burr on a critical edge. Check whether a turned feature on a milled part really needs turning at all.
A ten-minute DFM pass on the model often cuts far more cost than a long price negotiation later.
What an experienced buyer does next
Related reading: GD&T basics for procurement engineers: the 10 most common callouts.
The right move is usually to define the real functional requirement, remove the decorative requirements, and let the supplier build a route around what actually matters.
Comparison table where relevant
| Checklist item | Good practice | Cost risk if ignored |
|---|---|---|
| Internal corners | Use realistic tool radii | Small tools, slow cycle |
| Deep pockets | Keep depth-to-width ratio reasonable | Long tools, chatter |
| Thin walls | Add stiffness where possible | Deflection and scrap |
| Over-tolerancing | Tighten only functional features | Higher inspection and cycle time |
How to specify this in your RFQ
Include a clean 2D print, 3D model, material, finish, and note which features are function-critical. If there is a preferred machining orientation, state it. If there is no preference, say the supplier can optimize the setup. That freedom often saves money.
A clean RFQ does not just list requirements. It separates must-haves from preferences so the supplier can optimize where it is safe.
Have a part that needs quoting? Email your drawings to rfq@precisionmachining.co -
we return a competitive quote within 24 hours. Phone: +1 312-579-0808.