Tooling cost per part, and three ways to reduce it

Tooling has an awkward property: it is bought in boxes on a purchase order and consumed one part at a time on the floor. Nothing connects the two automatically, so it tends to sit in overhead as "shop supplies" — where it is invisible, and therefore never improved.

Getting it out of overhead and onto the part is a small piece of arithmetic with a large effect on what you can see.

Converting a box of tools into a cost per part

Cost of the tool divided by the number of parts it makes before it is changed. For an indexable insert, remember it has several usable edges — the cost per part is the insert price divided by edges, divided by parts per edge.

Do this for the tools that actually dominate: usually two or three of them account for most of the spend, and the rest genuinely are shop supplies. Chasing every drill bit is how this exercise stalls.

Measuring tool life without buying anything

You do not need monitoring hardware. Ask the operator to write the part counter reading on a card at each tool change for a couple of weeks. The difference between two entries is tool life, in the only unit that matters for costing — parts.

Expect scatter between changes, and do not smooth it away. Wide scatter is itself a finding — it usually means tools are being changed on judgement rather than on a rule, and that is a cost you can address.

Three reductions the same number can prove

Once tooling is a measured cost per part, three improvements become measurable rather than arguable:

1. Change tools on a count instead of on judgement. Tools pulled early waste life you paid for; tools run too long scrap parts worth more than the tool.
2. Use every edge on an indexable insert. Edges left unused are money already spent and thrown away, and this is more common than shops expect.
3. Consolidate part numbers. Fewer tool types means better prices and less stock sitting on a shelf, and it costs nothing in cutting performance if the tools were interchangeable anyway.

Where this guide stops

This guide covers **how to measure and record** tooling cost. It does not tell you what speed to run, which grade to buy, or when a tool is worn — those depend on your material, your machine and your part, and you know them better than any general document can.

What is hard to do alone is the rest: keeping the before and after side by side, keeping the revision history of who changed which number and why, and having someone else in the trade confirm or challenge it with their own figures.