This sets lead-in and lead-out feedrates. The default is 0.5, Router-CIM's standard 50% feedrate for lead-in and lead-out.
Setting the parameter to a number less than 1.0 is a percentage of max feedrate set in the Control Panel.
Setting the parameter to a number greater than 1.0 will give you an exact feedrate.
Setting the Leadfeed to 180 on a cut where the normal feedrate is 600, would allow the feedrate to be slower on the lead in than normal. Normally the lead in would be 300. In the code the lead move feedrate would appear on the same line as the lead.
%
:1234
N1 G00 G17 G20 G28 G40 G80 G91 Z0 M5
N2 G90
N3 G52 X0 Y0 Z0
N4 G08 P1
N5 M08
N6 (ROUTER-BIT .5 DIA.)
N7 G28 G91 Z0 M05
N8 G90 T2001 M06
N9 T102
N10 M03 S18000
N11 G00 G17 G55 X5. Y-.249
N12 G00 G43 H1 Z.25
N13 G01 X3. Z-.75 F180. <<<<<< Lead In feedrate here.
N14 X.5 F600. <<<<<< Normal cut feedrate here.
N15G02 X-.249 Y.5 J.749
You could also set the Leadfeed in the example above to 0.3 and get the same result as 180 is 30% of 600.