You send one drawing to three suppliers and get three very different numbers back. Before assuming the cheapest is cutting corners or the dearest is padding, it is worth understanding what actually goes into the figure.
What the unit price contains
A machined part price is built from four blocks:
Material. Bar stock or plate, plus the offcut you pay for but never see. A part machined from a 60 mm block that finishes at 40 mm carries the cost of the material that became chips.
Machine time. Setup plus cycle. Setup is amortised across the batch, which is why a quantity of 10 and a quantity of 100 rarely differ by a factor of ten.
Secondary operations. Deburring, tapping, heat treatment, surface finishing. These are often quoted as a lump and are the most common place for two quotes to diverge.
Inspection. First article, in-process checks, final. On a part with tight callouts this can be a real share of the cost.
The questions that reveal the difference
Rather than asking for a discount, ask these:
*What quantity is this price based on, and what changes at double that quantity?* A supplier who cannot answer immediately has not thought about your batch.
*Is surface finishing included, and to what standard?* "Anodised" is not a specification. Type, class and colour all move the price.
*What inspection is included in the unit price, and what would a full dimensional report cost?* Many quotes assume a sampling plan. If you need an FAI on every batch, that belongs in the number from the start.
*Is tooling or fixturing included, and who owns it?* On repeat orders this matters more than the unit price.
Where the honest differences come from
Two suppliers quoting the same drawing can legitimately differ because:
- One has the right machine free and one does not. A part that fits a mill-turn centre in a single setup is genuinely cheaper than the same part done in three operations.
- One is quoting a soft-jaw setup and one a dedicated fixture. Cheaper per setup, dearer per piece, or the reverse.
- One has read the tolerance block literally and one has read the critical features. This is the most common cause of a large gap, and it is worth asking about, because it tells you who read your drawing.
Signals worth paying attention to
A quote that arrives with questions is usually a better sign than one that arrives instantly. Questions about datum choice, thread callouts or finish standards mean an engineer opened the file.
A quote that is dramatically lower with no questions asked often reflects a different reading of the drawing rather than a different cost base. That difference surfaces later, at inspection.
Before you place the order
Agree three things in writing: what inspection report comes with the shipment, what happens if a dimension falls outside the drawing, and what the lead time is measured from — order date, drawing approval, or payment. Most disputes we have seen in this industry trace back to one of these three never being written down.
