Methodology / Lead time

Lead time — definition and counting

Time from order and drawing confirmation to dispatch, queueing included, excluding customer-side delays.

Unit

days

Formula

scheduling queue + material preparation + machining + surface finishing (outsourced) + inspection + packaging

Why suppliers disagree

• Sample versus batch: seven days and 45 days are both normal and cannot be quoted as one number
• Whether queueing is included; when capacity is full, queueing can be half the lead time
• Outsourced steps: anodising and heat treatment are frequent bottlenecks the plant does not control
• Inspection: full inspection versus sampling differs by days
• Holidays: the month around Chinese New Year is effectively lost capacity

How to collect it on site

• Ask how many days the last comparable batch actually took, not how long it usually takes
• Ask for three months of order-to-dispatch records
• Ask which subcontractor handles finishing and what their lead time is
• Record promised lead time and actual lead time separately

The three most common misreadings

1. Quoting stock-item lead time for a custom part
2. Ignoring subcontractor queues; finishing shops can add two weeks in peak season
3. Treating 'scheduled' as 'started'