What are ramps and lead-ins, and when does a beginner actually need them?

The two features, untangled

RAMPS control how the bit ENTERS DEPTH. Instead of drilling straight down (the center of a bit cuts poorly, see the plunge-marks entry), the bit descends while moving forward along the cut. The Profile toolpath has three ramp types on its Ramps tab:

• Smooth: ramps into the material using a set Distance or Angle
• Zig Zag: ramps down by going back and forth over a set distance
• Spiral: a continual ramp down around the whole profile. Spiral is only available when the toolpath has no lead-in moves.

The Pocket toolpath has a single Ramp Plunge Moves option with a distance. All ramp moves are performed at the plunge rate of the current tool.

LEADS control WHERE the bit meets the profile edge. A lead-in brings the bit onto the cut line from the side (and a lead-out takes it away), so the entry mark that every plunge leaves lands off the finished edge instead of on it. The Profile form offers a Straight Line Lead and a Circular Lead.

When a beginner actually needs them

Ramps: almost always, on anything deep.

• Pockets and profile cuts more than about 1 pass deep: ramp ON, with a ramp distance of 2 to 3 times the bit diameter. This is a community starting point, not an official rule. A community recipe for snapped 1/4" bits on plunge is a ramp distance of 2x the diameter with a plunge rate of half the feed rate.
• Plastics and aluminum: strongly recommended, because dwelling melts or welds (see those entries)
• Shallow V-carves and engraving: not needed (V-carve manages its own entries)

Leads: when the edge is the show.

• Visible profile edges on finished pieces (cutting boards, plaque edges): a small lead-in, with a lead length of about 1/8 to 1/4" as a starting point (shop advice)
• Parts that get sanded or rounded over anyway, or interior waste cuts: skip them
• Inlay pockets and plugs: leads help keep walls pristine

Pro tips

• Start point choice matters with leads. Put the entry on the least visible edge (in Node Edit, press P to move the start, a method from the software maker's user forum).
• The ramp options are easy to miss: on Profile they are on the Ramps tab, and on Pocket they are the Ramp Plunge Moves checkbox. Beginners miss them and blame the bit for entry burns.
• If an edge shows a little divot where the cut began, that's your missing lead-in.