Guides / Cost
Where the Weeks Actually Go on a Heavy Machined Part
September 3, 2026
A buyer sees twelve weeks on a quote for a part with sixty hours of machining in it and assumes the shop is padding. Usually it is not. On heavy parts the machine is rarely the longest item, and most of the elapsed time is spent waiting rather than cutting.
A realistic breakdown
Take a welded steel housing, three tonnes, with bores that need to line up.
| Step | Typical elapsed time | Working or waiting |
|---|---|---|
| Drawing review and RFQ questions | 2 to 5 days | Working |
| Plate supply and cutting | 1 to 3 weeks | Mostly waiting |
| Welding and weld inspection | 1 to 2 weeks | Working |
| Rough machining | 2 to 5 days | Working |
| Stress relief, including transport if off site | 3 to 10 days | Mostly waiting |
| Finish machining | 3 to 8 days | Working |
| Inspection and report | 1 to 3 days | Working |
| Surface treatment, if any | 3 to 10 days | Mostly waiting |
| Crating and transport booking | 3 to 10 days | Mostly waiting |
Add it up and the machining is a couple of weeks inside a twelve week programme. These are typical ranges, not promises, and they move with how busy each link is.
The items that usually decide it
Blank supply. Plate of an unusual thickness, a forging, or a casting from a foundry with a queue. This is the most common single constraint and it is also the most compressible, because the blank can often be released before the final machining drawing is.
Oven availability. Stress relief needs an oven big enough for the part, and large ovens are not on every site. If the cycle is sub-contracted, add transport each way and the sub-contractor’s own queue.
The machine being free. Heavy machines are booked in days, not hours. A shop with the right machine fully loaded for five weeks cannot start your part sooner however much you pay, and honest shops will tell you the date the machine is free rather than a nominal lead time.
Sub-contract steps. Heat treatment, grinding, painting, balancing. Each one is a transport cycle plus somebody else’s schedule.
Transport. Oversized freight needs permits and a booked slot. See shipping oversized machined parts.
Where you can actually compress it
Release the blank early. If the outside dimensions and the material are settled, the blank can be ordered and welded while the detail drawing is still being finalised. This alone often saves two to three weeks.
Decide the sequence question early. Whether stress relief is in the plan changes the schedule by a week or more. Deciding it at kick off rather than after the first quote round avoids a replan.
Reduce the number of sub-contract steps. Ask what is in house at each shop. A shop that welds, machines and stress relieves under one roof can be meaningfully faster than a cheaper shop that sends three steps out.
Relax the tolerances you do not need. A looser positional requirement can remove an overnight thermal stabilisation and a re-cut cycle. See tolerance across a large part.
Book the transport when you place the order, not when the part is finished.
Split the order. If you need four pieces and only need one urgently, say so. The first piece can ship while the rest are in the oven.
Where you cannot
The foundry. If the blank is a casting and the pattern does not exist, nothing else you do matters for several weeks.
Cooling. A thermal cycle cools at a controlled rate. That rate is a metallurgical requirement, not a scheduling preference.
Weld inspection. If the procedure calls for non-destructive testing after welding, it happens on its own timescale.
How to ask so the answer is useful
Do not ask for the lead time. Ask for the schedule:
Please give the lead time as a sequence with dates: blank available, welding complete, rough machining, stress relief out and back, finish machining, inspection, ready to ship. Also tell me which step is the constraint.
The answer tells you where to push and stops you paying an expedite fee to a shop whose machine was never the problem.
What to do next
Ask every quote which step is the constraint. If three shops name the same one, that is your real lead time and no amount of supplier switching will change it. If they name different ones, the shop with the shortest constraint is worth a closer look.
Related: comparing heavy machining quotes.
Frequently asked questions
Why is the quoted lead time so much longer than the machining hours?
Because machining is one item among six or seven. Blank supply, stress relief, sub-contract steps, inspection and transport each add days, and most of that time is queueing rather than working.
What is the fastest thing I can do to shorten it?
Release the blank early. On most heavy parts the blank is the longest single item, and it can usually be started before the machining drawing is finally approved.
Is paying for expedite worth it?
Only if the constraint is the machine. If the constraint is an oven queue or a foundry, expedite money at the machine shop buys nothing. Ask which item is the constraint before you offer to pay.
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