Touch drill bit against the end of the workpiece.

Put a bit of square bar or back end of a tool bit in the toolpost and bring it upto the front of the chuck, zero handwheel dial.

Now move the bar towards the work by the depth of your hole using hopefully more accurately marked graduations.

Drill hole until the bar stops the chuck going any further,

Bit of masking tape round the drill at the designated distance. If that isn’t accurate enough you need to decide if it is the tip of the drill or the edge that is your required distance then clean up the hole with a D-bit.

Sometimes a semi-sacrificial tool is the way to go. Drill a through hole is a suitable bit of material to make a sleeve and fit a setscrew to clamp it to the drill. Adjust so the drill projects the same as the depth needed and make the hole.

Once done put it the possibly useful bits box for next time. Which will either never happen or, if it does, the tool will have migrated to that dimension that stores stuff until the week after you need it!

Generally best to go touch undersize when drilling so the sleeve has t be worked onto the drill. I’d do the setscrew hole before drilling.

Good way to get some use out of the short ends that aren’t long enough to hold in the chuck.

Clive