CAM basics

CNC Toolpath Types Explained: Profile, Pocket, V-Carve and 3D

Open any CAM program and you're faced with a menu of toolpath types. They all move a spinning bit through material, but each one is built for a specific job, and choosing the wrong one wastes time, bits and stock.

This guide explains the toolpaths you'll use most on a hobby CNC router, what each is for, which bits pair with them, and the settings that trip people up. The names vary a little between programs, but the concepts are the same everywhere.

A few terms first

Profile (contour) toolpaths

A profile follows a vector line. The key setting is which side of the line the bit runs on.

• Outside: the bit runs outside the line so the finished part matches your drawing. Use it to cut a part out of a sheet.
• Inside: the bit runs inside the line so a hole matches your drawing. Use it for cutouts and openings.
• On the line: the bit's center follows the line, leaving a groove as wide as the bit. Use it for decorative lines and slots matching the bit diameter.

Tips for profiles

• Add tabs on through-cuts, or use another way of holding the part (screws in the waste, tape and glue, or a vacuum table).
• Consider a small finishing allowance and a final light pass for cleaner edges and better dimensional accuracy.
• Use ramping instead of straight plunges where your CAM supports it. It's easier on the bit.
• Remember an end mill can't make a sharp inside corner. It leaves a radius equal to the bit's radius. Design for it, or use "dogbone" or "T-bone" corner relief for parts that must fit together.

Pocket toolpaths

A pocket removes all the material inside a closed shape down to a set depth: a recess for a coin, a tray, a drawer insert, a flat area under a raised logo.

Clearing strategies

• Offset: the bit spirals around following the shape's outline. Good edge finish, consistent engagement.
• Raster: back-and-forth lines across the pocket, usually followed by a profile pass around the edge to clean it up. Often faster in large, simple pockets.
• Adaptive / high-efficiency clearing (in some CAM programs): keeps the bit's engagement constant, allowing deeper cuts with a smaller stepover. Useful in harder materials, including aluminum, on less rigid machines.

Choosing a bit

Use the largest bit that fits the pocket's smallest inside feature, because a larger bit removes material faster. If the pocket has tight corners, many CAM programs let you clear with a large bit, then use a smaller bit just to clean up the corners. This is often called rest machining or a clearance tool + finish tool combination.

V-carve toolpaths

V-carving is the toolpath that makes CNC signs look professional. A V-bit cuts deeper where the shape is wide and shallower where it's narrow, so the walls come up to a sharp point. The result is crisp lettering with sharp inside corners that a flat end mill can't produce.

• The bit's angle (for example 60 or 90 degrees) affects the look. Steeper angles cut deeper for the same width.
• Wide areas would require very deep cuts, so most programs offer a flat depth option. The V-bit stops at a maximum depth and a separate flat-bottom bit clears the remaining floor.
• V-carving is also how CNC inlays are made, where a matching male and female carving fit together.

Our V-bit guide covers which angles suit which work.

Engraving and "follow vector"

A simple engrave or "follow vector" toolpath drives the bit along a line at a fixed depth. It's used for single-line fonts, outlines, and drawing-style designs. The width of the line comes from the bit: a fine engraving bit or small V-bit at a shallow depth gives a thin line. It's different from V-carving because the depth doesn't vary with the shape.

Drilling toolpaths

Drilling plunges at points, usually circle centers. Many routers use an end mill rather than a drill bit. For holes larger than the bit, use a small pocket or inside profile instead. "Peck" drilling (going down in steps and retracting to clear chips) helps with deeper holes and harder materials.

3D roughing and finishing

For curved, sculpted shapes (relief carvings, bowls, terrain maps, molds), CAM works from a 3D model and creates two toolpaths.

1. Roughing: a larger flat end mill removes most of the material in stepped layers, leaving a "staircase" a little above the final surface.
2. Finishing: a ball-nose bit follows the actual 3D surface with a small stepover. The smaller the stepover, the smoother the surface and the longer the job.

The finishing stepover is the main trade-off between quality and machine time. Fine stepovers on a large carving can mean very long run times, during which someone still needs to be with the machine. Tapered ball-nose bits give fine detail with more strength than tiny straight ball-nose bits.

Choosing the right toolpath: a quick table

Putting toolpaths in order

Most real projects use three or four toolpaths. A typical sign might be a V-carve for the letters, a pocket to clear a flat area, a profile to round the edges, and an outside profile to cut it free. A good order:

1. Surface or flatten the stock if needed.
2. Do detailed work (V-carving, engraving) while the part is fully supported.
3. Clear pockets and inside profiles.
4. Run the outside profile last, with tabs or secure workholding.

Group toolpaths by bit to minimize tool changes, as long as that doesn't break the "outside last" rule. After every tool change, re-zero Z with a touch plate or tool setter.

Where the numbers come from

Every toolpath needs feed rate, spindle speed, depth per pass and stepover. These depend on your machine, the material and the bit, so there's no universal list. Start from the bit manufacturer's recommended chart or the tool library in your CAM program, then run a short test in scrap of the same material. Listen to the cut and look at the chips. Our feeds and speeds guide explains chip load and how to adjust from a starting point.

Bottom line

A basic set of end mills, a couple of V-bits and one tapered ball-nose cover every toolpath in this guide.