Machinists use this phrase when making tiny, iterative adjustments to a setup to achieve tight tolerances. It originally refers to using a dial indicator to measure runout or alignment, tapping the workpiece until the needle barely moves. The phrase applies broadly to tweaking feeds and speeds, fixture alignment, or offsets until the resulting cut is exactly right.
I had to dial it in for an hour before the runout on that shaft dropped below a tenth.
Related terms
Indicate
To align a vise, part or bore to the machine axes using a dial or test indicator.
Sweep
To rotate an indicator in the spindle around a bore, boss or circle to find its center or check alignment.
Tenth
One ten-thousandth of an inch (0.0001 in, about 2.5 microns), the unit of precision grinding and fits.
Runout
The amount a rotating tool or workpiece wobbles off its true centerline.
Feeds and speeds
The spindle speed and feed rate chosen for a cut, set from material, tool and machine.