Using a 'dog' and lantern a collet

You mount your gear with a pivot in need of burnishing, or in the example here; some raw cut pivots. We made small brass carriers for the 'ears' of the dog to lock onto. You can see the bow twisted around it. As you operate the bow, it spins the dog, which the ears engage the spokes of the gear or in our case, the long screw of the carrier.

In motions opposite of your bow, you place your burnisher atop the pivot which rests in a lantern collet slightly smaller than the target you plan to size your pivot to. For example, you want to cut your pivot to .25mm, you'd use a groove in the collet sized to .22mm or .20mm. That way the burnisher doesn't bottom out and some material of the pivot sticks up, able to be cut.