# How cutting data works

How cutting parameters are structured, where operations come from, and how the machining calculator uses them.

Source: https://support.toolingmetrics.com/en/library/overview/cutting-data/
Updated: 2026-10-29

:::caution[Verify before machining]
Calculated speeds, feeds and depths are starting values. Before you machine, check the tool geometry, units, cutting parameters and the machine's limits against the tool manufacturer's data and your shop's procedures. See section 10 of the [Terms of Service](https://toolingmetrics.com/eng/legal/terms).
:::

## What a cutting data entry represents

A **Cutting Data** entry is a recorded answer to one specific question: "at what speed and feed does this tool assembly cut this material, for this operation?" It always ties together three things — a tool assembly, an operation type, and a workpiece Material — because the right cutting speed for a drill in aluminium is meaningless applied to the same drill in hardened steel. An assembly accumulates one entry per material/operation combination it has actually been run at, which is why the same assembly can carry several cutting data entries side by side.

## Where operations come from

A Product only supports the operations recorded on it — drilling, shoulder milling, external turning, and so on. These are parsed automatically from its `.p21` data file, or set by hand when no file is available (see [How the Product Catalog Works](https://support.toolingmetrics.com/en/library/overview/product-catalog/#how-operations-affect-downstream-workflows)). Operations gate the machining calculator: without at least one operation set on the cutting product, there's nothing for the calculator to compute cutting data against.

Not every operation type has a working calculation, either. Trepanning and the two broaching operations can be recorded as cutting data — Vc, fz, ap, ae all save normally — but the calculator doesn't yet derive spindle speed, feed rate, or power for them. That's a gap in the formula set, not a data-entry mistake.

## Why some results are blank

The calculator always computes Spindle Speed, Feed Rate, and Material Removal Rate from geometry and the parameters you enter. Cutting Power and Torque are different: they require the workpiece material to have a specific cutting force (*kc*) value on record. A material with no *kc* data simply can't produce a power estimate — the calculator isn't failing, the input it needs isn't there. This is the practical reason to prefer materials from the preloaded database over ad-hoc custom entries where possible: preloaded materials are more likely to carry *kc*.

## How the calculator and the assembly stay in sync

The machining calculator is the cutting data form on a tool assembly line, not a separate tool. Opening it from an assembly's **Cutting Data** tab pre-fills geometry from that line's cutting product. Opening an existing entry loads its saved Vc/fz/ap/ae values, so refining a calculation starts from what's already been proven to work, not from a manufacturer's generic starting point. Saving writes to that entry, which is also what a project operation and the setup sheet read from later. There is only one place cutting data lives; the calculator is a view onto it, not a separate record.