Guides / Cost
Why Two Quotes for the Same Large Part Differ by Thirty Percent
September 17, 2026
On small parts, three quotes for the same drawing land within about ten percent of each other. On large parts they routinely differ by a third, and buyers reasonably assume someone is padding.
Usually nobody is. The shops are quoting different jobs, because a heavy drawing leaves more room for interpretation than a small one. Here is how to find the difference.
First, normalise the scope
Before you compare numbers, get each quote to answer the same six questions.
- Who supplies the blank? A quote that includes buying and welding a steel fabrication is not comparable to one that machines a blank you deliver.
- Is stress relief included? This is the single biggest source of spread on welded and heavily roughed parts. See stress relief before finish machining.
- How many setups? Each re-clamp is handling time, crane time and another chance to lose position.
- What inspection is included? In-process probing and a written first article report cost real hours. A quote without them is cheaper and proves less.
- What finishing is included? Deburring, painting, preservation and marking.
- What does the price include on freight? Ex works, delivered, crated, uncrated.
Once those six line up, most of the gap is gone.
Where the money actually sits
On a heavy part the cost structure looks like this, roughly in order of size:
Machine hours. The machine is booked for days. On a large boring mill or gantry the hourly rate is several times that of a machining centre, and it dominates everything else. This is why removing unnecessary finish passes saves more than negotiating on margin.
Handling. Rigging, craning, turning over, re-indicating. Shops price this separately because it needs a crane and often a second person. A part that needs four setups carries roughly twice the handling of one that needs two.
Stock removal. Not the price of the steel, the hours to turn it into chips. A blank that arrives 15 mm oversize everywhere costs shifts of roughing before finishing starts.
Process steps outside machining. Oven time, transport to a sub-contractor, queue time at that sub-contractor.
Freight and packing. On very large parts this is not a rounding error.
There is a fuller breakdown in what a large part machining quote is made of.
The questions that explain a gap
When one quote is far below the others, ask the cheap shop these:
- What sequence are you planning, and does it include stress relief?
- How many setups, and where are the datums?
- What machining allowance are you assuming on the blank?
- How will you prove the bore position across the part?
- What happens if the part moves after roughing, and who carries that?
And ask the expensive shop:
- Which part of this drawing is driving the cost?
- Is there a tolerance you would relax if I let you?
- Would a different blank type reduce your roughing?
That last pair is worth more than any negotiation. Experienced heavy shops will usually tell you exactly which callout is expensive, because they would rather win the job with a cheaper sequence than lose it on price.
Lead time is part of the comparison
A quote that is ten percent cheaper and six weeks later is not cheaper if the equipment it goes into is waiting. Ask when the machine is actually free rather than the nominal lead time, and ask whether the sub-contract steps are booked or assumed.
See where the weeks go on a large part.
A practical comparison sheet
Put the quotes side by side with these rows and the winner usually becomes obvious:
| Row | Why it matters |
|---|---|
| Blank supplied by | Changes the scope more than anything else |
| Machining allowance assumed | Drives the roughing hours |
| Stress relief included | The classic hidden difference |
| Number of setups | Handling and position risk |
| Inspection included | What you get as proof |
| Surface treatment | Often assumed, rarely stated |
| Incoterm and packing | Can be a large number on heavy parts |
| Machine the part runs on | Tells you whether the route makes sense |
| Delivery date, machine free from | The real lead time |
What to do next
Send all three shops the same clarifying email rather than chasing each separately. You will get back comparable scopes in a day, and the price you finally accept will be for the job you actually wanted.
If you are still writing the request, the eight things a heavy quote needs from you prevents most of this work up front.
Frequently asked questions
Should I always take the middle quote?
No. Work out what each quote includes first. Once scopes match, the spread usually collapses, and the remaining difference is machine rate and how busy the shop is. Pick on scope and sequence, then on price.
What if a shop will not break down the quote?
You do not need a cost breakdown. You need a scope statement: how many setups, whether stress relief is in, who supplies the blank, what inspection is included and what the freight covers. A shop that will not say is a shop you cannot compare.
Is the cheapest quote usually wrong?
Not wrong, but usually shorter. The cheap quote is often the one that plans fewer setups or leaves stress relief out. That can be the right call on a loose part. On a tight one it moves the risk to you.
Need a quote for a part like this?
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