The Drawing Checklist That Gets You A Firm Machining Quote
What to put on the print so the quotation comes back firm instead of hedged.
Four Things That Decide The Price
Material, tolerances, quantity and finish. Miss any one and the supplier either asks or guesses, and a guessed quotation is worth nothing to either of us.
- Material grade, not just family
- Tolerances on the features that matter, general tolerance elsewhere
- Annual quantity and batch size
- Surface finish and any coating
Tolerance Everything Tightly And You Pay For All Of It
A blanket tight tolerance across a drawing is the single most expensive habit in machined part buying. Tighten the features that have to fit, relax the rest, and the price falls without the part getting worse.
Threaded Flange Bushing With Knurled Collar
Datums Are Not Decoration
Tell the supplier which face or bore the part is located from in the assembly. That decides the machining sequence, and picking the wrong datum is how parts pass inspection and still fail to fit.
Say What The Part Does
Two lines describing the function let an engineer spot the feature that will cause trouble. Most of the useful comments we send back come from that paragraph, not from the dimensions.
Send Samples If You Have Them
When a part is moving from another supplier, a current production sample tells us what the drawing does not: what the previous shop actually held, where the part has been adjusted, and what your inspection really checks.
More Guides
Why Slender Parts Are Machined On Swiss-Type Lathes
What a guide bushing actually does, and why a long thin shaft behaves differently on a sliding-head lathe.
What To Check Before Importing Machined Parts From China
How to separate a machine shop from a trading company, and how to structure a first order so it proves something.
Reader Questions
Can you quote from a 3D model only?
We can give an indication, but a firm quotation needs tolerances and datums, and those live on a 2D drawing. For prismatic parts a model plus a dimensioned print is the usual combination.
How long does a quotation take?
Usually a few working days once the drawing, material and quantity are in hand. Incomplete information is what stretches it.
Do you comment on the design?
Yes, as part of quoting. If a feature is expensive or fragile we say so and suggest an alternative, which you are free to ignore.
Send The Drawing And Find Out
Material, tolerances, quantity and finish are enough for a firm number. Anything missing, we will ask in the first reply rather than guess.