Guides / Cost

The Five Things That Turn a Request Into a Real Quote

September 23, 2026

There are two kinds of machining quote. One is a number the shop can stand behind because it could see everything it needed. The other is a number with a cushion in it, sized by how much the shop had to guess.

The difference is entirely in what you send. Here is what makes a quote real.

1. Geometry the shop can open

In order of how much they help:

What you send	What the shop gets	Good enough to quote?
STEP or IGES	Exact surfaces and dimensions	Yes
PDF drawing with dimensions	Intent, tolerances, callouts	Yes, with the model
DXF or DWG	Flat profiles, good for plate parts	For 2D parts
STL or 3MF	A mesh approximation of the shape	No, reference only
Photos with a ruler	A rough idea of size and features	Only with measurements
Native CAD files	Often nothing, if the shop runs other software	Not on its own

STEP is the format to ask your CAD for. Nearly every package exports it and nearly every shop can open it. If you have a model and a drawing, send both. The model carries the shape and the drawing carries everything the shape cannot say.

2. Material and temper, written out

“Aluminum” is not a material specification. “6061-T651 plate” is.

Say the alloy, the temper and, when it matters, the form. For steel add the condition and whether it is hardened before or after machining, because that decides whether features get ground afterwards.

If you genuinely do not know, describe what the part does and let the shop propose something. That is a better outcome than a guess that nobody wrote down.

3. The quantity you actually want

Quantity moves the price more than anything except the part itself, because setup spreads across it.

Give the shop three numbers if you can: what you need now, what you expect over a year, and whether it repeats. A shop that knows 25 pieces will become 100 will fixture the job differently and quote the first batch lower.

4. Only the tolerances that matter

This is where most money gets lost. A drawing with every dimension tightened out of habit prices like a precision part, and the extra precision buys nothing.

Mark the features that have to be right: bores that take a bearing or a bushing, faces that clamp or seal, the positions that must line up with something else. Put a general tolerance block on everything else, typically plus or minus 0.1 to 0.25 mm for a machined automotive part, and say so on the drawing.

The same goes for surface finish. Call out Ra where it matters and leave the rest as machined.

5. Context, in one or two sentences

Tell the shop what the part is, what it bolts to and what happens if it fails. It takes a sentence and it changes how the part is quoted and made.

A bracket holding a wiring loom and a bracket locating a suspension arm can look identical on a drawing. One is a simple job. The other needs material certification, attention to the fillet radii and possibly an inspection report.

The five things buyers forget most often

1. The finish. Anodizing, plating, powder coat, bead blast. If it is not on the drawing, the part arrives as machined.
2. Edge condition. “Break all sharp edges” is one line and it saves cut fingers and stress risers.
3. Threads. Size, pitch, depth, and whether they are through or blind.
4. Marking. Part number, revision, orientation arrow. Cheap when it is in the program, expensive afterwards.
5. When you need it. A date, not “as soon as possible”. Shops schedule around real dates.

An RFQ template you can copy

Paste this into an email or into the notes field on an RFQ form, fill in what you know and say plainly where you are unsure.

Part: front engine mount bracket, one side
Quantity: 2 now, likely 20 next year
Material: 6061-T651, happy to be advised
Files: STEP attached, PDF drawing attached
Critical: two 12.00 H7 bores, 84.00 mm between centers
Also critical: mounting face flat within 0.05 mm
General tolerance: plus or minus 0.15 mm unless marked
Finish: clear anodize
Threads: 2 x M8 x 1.25, 16 deep
What it does: bolts to the block, carries the mount bush
Needed by: 14 November
Notes: original is cast and cracked, photos attached

Everything in that block is something the shop would otherwise have to ask about or price defensively. Ten minutes writing it will usually save more than it costs.

What not to send

• The entire assembly model when only one part is being made
• Twenty photos with nothing in frame for scale
• A screenshot of a part on someone else’s website with “like this but stronger”
• A drawing with every dimension boxed as critical
• A deadline of yesterday with no drawing attached

None of these are fatal. They just move the conversation from quoting to guessing, and guesses cost money.

Send what you have and we will tell you what is missing before it goes to any shop. For the full sequence from idea to part, start at the buyer’s guide, and see what actually drives the cost for where the money goes.

Frequently asked questions

Keep reading

• What a Custom CNC Auto Part Actually Costs
• Where Aftermarket Car Parts Buyers Meet Suppliers in 2027 and 2028