One part number, one process, one heat
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The definition
A quantity of fasteners of one part number fabricated by the same production process from the same coil or heat number of metal as provided by the metal manufacturer.
One part number
So two sizes together are not a lot, which is the obvious condition and the one a sorted jar already satisfies.
The same production process
So the same part number made on two lines, or by two methods, is two lots rather than one.
And the same coil or heat number of metal
Which is the condition that reaches upstream, and it is the one a jar can break by accident.
As provided by the metal manufacturer
So the heat number is not the fastener maker's invention. It comes from the mill and travels with the steel.
Which makes a lot a traceability construct
A quantity you can follow back to one batch of metal, which is the whole point of defining it.
And traceability is destroyed by combination
Two lots in one container are not one larger lot. They are two lots you can no longer tell apart.
Which is irreversible in a way most container failures are not
A wrong container can be changed. A mixed jar of identical bolts from two heats cannot be unmixed.
So the practical rule is one lot per container
Which is a simple discipline with a real consequence, and it is the only thing a container can contribute here.
And a container big enough to tempt a top-up is the risk
Our shelf runs to 500 mL with a median of 177. A half-empty jar invites the next bag being poured in.
Which is an argument for the small end
60 of the 251 containers are under 60 mL and 22 are under 30. One lot per small jar is easier to keep honest than one lot per large one.
And for labelling at fill time
Because the heat number is on the bag the fasteners came in, and that bag is about to be thrown away.
We publish nothing that helps
Ten specification fields and not one is a lot number, heat number, coil reference or production date.