The cog fitted to the axle.
https://files.mastodon.social/media_attachments/files/112/622/562/212/933/149/original/adb29e93cb9486d7.jpg
Managed to burn out my drill - motor's gone. So either another hundred and something quid on a new one, or £15 on a new motor (coincidentally saving the two perfectly good battery packs that don't work with current models).
But the new motor had a round axle, not the flattened side I need. So clamp the motor, needle nosed pliers to hold the axle (filing something that rotates is a nightmare), then clamp the pliers to the bench. Fiddly, but chuffed how well it worked.
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