A cutting rate is only one input to BTA drilling cost. The useful denominator is the delivered output defined by the quotation and its inspection requirement.
Name the charge boundary first
UNISIG’s construction discussion describes different tool-service arrangements. It supplies context for charges that might differ, but not a current price list or an economic threshold for a particular batch.
Keep setup, machining, consumables, tool service, inspection and any included finishing identifiable. State which charges are allocated to the batch and which are outside the comparison. Two totals can look comparable while covering different delivery stages.
A deliberately assumed batch example
The following values are arithmetic inputs, not a supplier quotation or observed production case:
| Included batch charge | Assumed currency units |
|---|---|
| Setup and machine time | 800 |
| Tooling and service | 240 |
| Inspection | 160 |
| Total | 1,200 |
With 100 accepted holes, the assigned cost is 1,200 / 100 = 12 units per accepted hole. With the same charges but 80 accepted holes, it is 15 units per accepted hole. A count of drilled holes cannot replace the accepted count when the purchased output is inspected delivery.
Compare a tool or process change on the same basis
If a proposed change affects cutting time, record the other included charges and actual accepted output as well. A shorter cut does not establish a lower delivered cost if the compared totals or products differ.
Retain the reference and changed assembly with the batch record. A service invoice for a sharpened item and a charge for an inspected ready-to-run head also cover different work.
Enter these assumed values in the accepted-hole calculator below to reproduce the denominator example, then replace them with the agreed job inputs. Continue to head service for the supplied tool state or the BTA/gundrilling economic comparison for aligning two complete routes.
Revision note
October 8, 2026: revised the technical explanation and connected reading after source review. Original publication date and URL retained.
