Guides / Choosing a Supplier
The Eight Things a Heavy Machining Quote Needs From You
September 19, 2026
Most delays in a heavy machining quote are not caused by the shop being slow. They are caused by an RFQ that is missing two or three facts the shop cannot proceed without, so the first reply is a list of questions rather than a price.
Here is what a shop needs, roughly in the order it checks them.
1. Overall envelope
Length, width and height of the finished part, in millimetres or inches, stated in the email as well as on the drawing. The shop is checking it against travel, table area and spindle to table height before it reads anything else.
Give the envelope of the blank too if it is much bigger than the finished part. A weldment that arrives 200 mm oversize on every face is a different job to one that arrives near net.
2. Finished weight
The single most useful line in a large part RFQ. It decides whether the table, the crane and the floor can take the part, and it is the fastest way for a shop to rule itself out honestly instead of quoting and backing out later.
An estimate is fine. Say it is an estimate.
3. What the blank is
Weldment, casting, forging, plate or solid stock. This changes the roughing plan, the amount of stock that has to come off, and whether stress relief belongs in the sequence.
Also say who supplies it. A shop that has to buy, weld or source the blank is quoting a different scope from one that machines a blank you deliver.
4. Material and its condition
Grade, and whether it is annealed, normalised, quenched and tempered, or as welded. 42CrMo4 in the soft state and the same steel hardened are not the same job.
For castings, say the foundry standard and whether the casting has been aged.
5. The tolerance that actually matters
Not every tolerance on the drawing. The one or two that the assembly genuinely depends on.
On a large part this is critical, because holding a feature is easy and holding two features in position across several metres is not. Say which relationships carry the function and which numbers are inherited from a template. Shops that know the difference quote a sequence that protects the real requirement. Shops that do not will either price for the worst case or miss it.
More on this in tolerance across a large part.
6. Quantity and whether it repeats
One piece, four pieces, or four pieces a year for five years. On heavy work the quantity curve is flat compared with small parts, because machine time per piece does not fall much, but a repeat order justifies a proper fixture and that does change the price.
Say plainly if this is a one off, a prototype for a series, or a spare.
7. Everything that is not machining
Welding, stress relief, heat treatment, grinding, painting, balancing, assembly, marking. Each of these is either in house at the shop, sub-contracted, or your problem, and the quote means something different in each case.
If you do not say, you will get quotes that include different scopes and they will not be comparable.
8. Where it has to go
The delivery city, port or plant. Oversized freight, crating and lifting arrangements can cost more than the machining on a very large part, and they change which shops are worth asking in the first place. A shop 500 km away that charges more per hour can still land cheaper than one an ocean away.
See shipping oversized machined parts for what drives that side.
What good looks like
A strong large part RFQ is short. Something like:
Welded steel gearbox housing, S355, stress relieved before finish machining. Envelope 2 400 x 1 100 x 900 mm, finished weight about 3.2 t. Blank is a weldment we supply, 12 mm machining allowance on the machined faces. Two bores 420 mm H7 on opposite faces, coaxial within 0.08 mm. Everything else is ±0.5 mm. Four pieces, repeat expected once a year. Painting not required. Delivery to Rotterdam. STEP and PDF attached.
That paragraph lets a shop decide in minutes whether it can take the part, and quote without a single clarifying email.
What to do next
Write those eight lines before you attach anything. If you cannot answer one of them yet, say which one is open rather than leaving it out. An RFQ with a stated unknown gets a useful quote. An RFQ with a silent unknown gets a padded one.
Then read how to compare the quotes that come back.
Frequently asked questions
Do I have to send a 3D model?
It helps, but a PDF drawing with datums and the critical dimensions is enough to get a quote on most large parts. What you cannot skip is the overall envelope and the finished weight, because they decide which shops can take the job at all.
Should I say which machine I want the part run on?
Usually not. Describe the part and which relationships have to hold, and let shops propose the route. A shop that owns a boring mill and a gantry will pick whichever gives you the better price for the same result.
What if the design is not finished?
Send it anyway and say so. A budget quote on an unfinished drawing is still useful, as long as both sides know that is what it is. Mark the dimensions that are fixed and the ones that may move.
Need a quote for a part like this?
Send the drawing with the envelope and finished weight. We match you with up to 3 shops that take parts this size and reply within 24 business hours.
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