G81

Hi,

Tried the drill tutorial in Deskam and wondering if others on the
list are familiar with the drill tutorial?

What is G81?

If one is using a 5/16" drillbit, what does a command like the one
below does?

N100 G81 x0.4 Y0.2 Z-0.3 R0.1 F10

The parameters given were

Tool : 5/16" drill bit
drill depth: 0.373
rapid ht. : 0.1
Tool dia. :

The input for the tool diameter appear to be irrelevant as
irrespective of whatever one input for the tool diameter, the above
remains ....R0.1

What is the significance of R0.1?

Or other examples (not from Deskam) like

N200 G81 R.50 Z-5

N300 G81 V1=5 V2=-7

What does these figures mean

Thanks

Ed