# grblHAL / FluidNC

For grblHAL and FluidNC controllers. The file is the same as for GRBL, with one addition: grblHAL can use a tool table.

## What the file looks like

The file starts with comments naming the project, the machine and the tools, then:

```
G21 G90 G17 G94
G54
```

Millimetres are `G21`; a profile that outputs inches writes `G20` instead. The spindle starts with
`S{rpm} M3` followed by a dwell (`G4 P` seconds) for the spin-up time in your profile, unless spindle
control is set to none. Cutting moves are straight lines only — `G0` for rapids and `G1` for cuts,
never arcs — and every line is 80 characters or fewer.

The file ends with:

```
G0 Z{safe}
M5
M30
```

## Tool changes

- **One file per tool** works: run the files in order and change the tool between them.
- **M6 and pause** writes `T{n} M6` then `M0`.
- **M6 with G43** writes `T{n} M6` and `G43 H{h}`, where `h` is the tool's length offset number, taking the tool length from the controller's tool
  table. Enable and fill the table first — it is your responsibility, and the file trusts it.

## Before the first run

Check your firmware's tool-change settings before choosing an M6 mode: what `M6` does depends on
how your grblHAL or FluidNC build is configured.

Set X and Y zero at the front-left corner of the piece and Z zero on the top of the stock, and run
the first file with the tool well above the work and a hand on the feed hold.