CNC Router Tips and Tricks for Better Woodworking

A CNC router opens up new possibilities in a woodworking shop. From cutting precise parts and joinery to carving intricate designs, a CNC can handle operations that would otherwise require considerable time and effort.

But getting the most from your CNC involves more than loading a design and pressing Start.

Choosing the right router bit, dialing in feeds and speeds, securing the workpiece, and planning efficient toolpaths all contribute to better results.

Woodsmith's Chris Fitch has spent years exploring these techniques through our CNC Basecamp video series. Along the way, he's developed practical tips for making CNC woodworking more accurate, efficient, and enjoyable.

Here are some of his favorite CNC router tips and tricks for working with wood, plastics, and even metal.

1. Combine CNC Machining with Traditional Woodworking

One of the biggest misconceptions about CNC woodworking is that the machine replaces traditional woodworking skills.

In reality, a CNC router can complement your existing tools.

For example, a CNC can remove the bulk of the material from a decorative carving. You can then use carving gouges and knives to refine the details and add the final hand-worked touches.

This combination saves time without sacrificing the character of traditional craftsmanship.

The same approach works for furniture parts, templates, joinery, and other woodworking projects.

Think of the CNC as another tool in your shop — one that's particularly good at repetitive cuts, precise shapes, and removing material.

2. Choose the Right CNC Router Bits

With so many CNC router bits available, choosing the right one can seem complicated.

You'll find upcut, downcut, compression, straight, single-flute, and multi-flute bits in a wide range of diameters and cutting lengths.

Although specialty bits have their place, Chris relies on two basic sizes for most routine woodworking operations:

• ¼"-diameter straight bit
• ⅛"-diameter straight bit

Both have relatively short cutting lengths.

These bits are versatile, durable, and reasonably priced. They work well for a variety of cutting and shaping tasks.

Check the Actual Bit Diameter

Not every router bit measures exactly what its packaging claims.

High-quality bits generally have more consistent dimensions, while inexpensive bits may be slightly undersized.

When accuracy matters, measure the bit with calipers and use the actual diameter in your CNC software.

Also inspect the cutting edge before each job. A dull bit can produce rough surfaces, excessive heat, and poor results.

3. Understand CNC Router Feeds and Speeds

One of the most important aspects of CNC machining is matching the feed rate and spindle speed to the cutting operation.

Feed rate describes how quickly the router moves through the material.

Spindle speed refers to how fast the bit rotates, measured in revolutions per minute (RPM).

Together with the number of cutting edges, these settings determine the chip load — the amount of material removed by each cutting edge as it passes through the workpiece.

Pay Attention to Chip Size

The chips produced during a cut can tell you a lot about what's happening.

Fine dust may indicate that the cutter is rubbing rather than efficiently removing material. This can generate unnecessary heat and shorten bit life.

Larger, well-formed chips often indicate a more efficient cutting action.

However, chip size alone doesn't determine whether a cut is correct. Bit geometry, material, machine rigidity, and surface quality also matter.

Starting Settings for Cutting Wood

Through experience, Chris has developed settings that work well with his CNC equipment.

For solid wood, plywood, and MDF, his commonly used settings include:

These are examples from Chris's shop, not universal settings.

Your machine may require different values depending on its power, rigidity, bit design, and workpiece material.

A chip load calculator and test cuts can help you find an appropriate combination.

4. Cutting Aluminum and Brass with a CNC Router

A CNC router designed primarily for woodworking can sometimes machine nonferrous metals, including aluminum and brass.

But cutting metal requires a more deliberate approach than machining wood.

The correct alloy, cutter, spindle speed, feed rate, lubrication, and chip removal all become especially important.

Choose Machinable Alloys

Chris recommends starting with materials known for their machinability:

• 6061 aluminum
• 360 brass

These alloys are generally easier to machine than many other metals.

Select the Appropriate Cutter

Chris's preferred starting choices are:

• Aluminum: Single-flute cutter
• Brass: Two-flute cutter

He has used settings around 18,500 RPM and 50 inches per minute for some metal-cutting operations, along with shallow cuts.

These figures should not be applied without checking the specific cutter manufacturer's recommendations and the machine's metal-cutting capabilities.

Manage Heat and Remove Chips

Chip evacuation is especially important when machining metal.

Accumulated chips can be recut, generating additional heat and reducing cutter life.

Chris uses compressed air to help clear chips from the cutting area.

Appropriate lubrication may also improve cutting performance, provided the machine and its components are compatible with the chosen lubricant.

Safety Note: Not every woodworking CNC is suitable for machining metal. Verify the manufacturer's approved materials, workholding requirements, and operating limits. Use appropriate guarding and chip collection, and keep hands clear of the cutting area. Avoid unapproved oil mist or spray systems.

5. Tips for Cutting Plastics on a CNC Router

Plastics offer another opportunity to expand what you can make with a CNC.

Materials such as acrylic and polyethylene can be used for decorative projects, templates, machine components, and other shop accessories.

But plastics present a different challenge: Heat can cause chips to soften and stick to the cutter.

The goal is to remove material efficiently while producing a smooth surface.

Choose the Right Bit for Plastic

Chris recommends starting with acrylic or polyethylene.

For cutting plastics, he suggests:

Prevent Melting and Chip Welding

When cutting plastics, Chris looks for a chip load in the approximate range of 0.004"–0.012", depending on the material and cutter.

If the plastic begins to melt or stick to the bit, he first considers increasing the feed rate, then reducing spindle speed.

The objective is to remove chips before excessive heat builds up.

These settings should be verified against the plastic and cutter manufacturer's recommendations.

For detailed carving, a smaller tapered ball-nose bit can produce a smoother finishing pass after the roughing operation.

6. Check Your CNC Setup Before Every Cut

Even an accurately designed toolpath can produce disappointing results if the machine isn't set up correctly.

Chris uses a checklist before starting a CNC job.

Preview the Toolpath

Always review the toolpath simulation in your CNC software.

Make sure the cutter follows the intended path and that the cutting depths and sequence look correct.

Verify the Workpiece Origin

Check the X and Y datum points.

Depending on the project, the origin may be located at the center or a corner of the workpiece.

Confirm that the software and machine use the same reference point.

Check for Obstructions

Make sure the router bit, spindle, and dust boot will clear clamps, screws, hold-downs, and registration blocks.

A simulated or manufacturer-approved dry run can help identify potential interference before machining begins.

Secure the Workpiece

Check that the material is firmly supported and held in place.

Suitable hold-downs, clamps, screws, and other approved workholding methods help prevent movement during machining.

Confirm Material Orientation

For plywood and solid wood, check that the grain direction matches the planned layout.

This can be especially important for visible project parts.

Recheck the Z-Zero Setting

After changing bits, confirm that the tool length and Z-zero reference are correct.

Forgetting this step can ruin a workpiece or damage a cutter.

7. Save Your CNC Router Settings

Once you've found a combination of cutter, material, and cutting settings that works well, save it.

Most CNC software includes a tool database where you can record information such as:

• Bit diameter and type
• Spindle speed
• Feed rate
• Plunge rate
• Depth of cut
• Material and cutting conditions

You can save multiple entries for the same bit when using different materials or cutting conditions.

This reduces setup time and provides a useful starting point for future projects.

8. Plan CNC Toolpaths for Better Efficiency

A CNC router can save considerable time in the shop, but inefficient toolpaths can make even simple projects take longer than necessary.

Chris recommends planning the machining sequence before starting the job.

Minimize Tool Changes

Whenever possible, group operations that use the same router bit.

This reduces the time spent changing cutters and resetting tool lengths.

Make Better Use of Your Material

Arrange parts to take advantage of the available cutting area.

Careful nesting can reduce material waste and allow you to machine several parts during one setup.

Compare Estimated Machining Times

Most CNC toolpath programs include a machining-time estimator.

Use it to compare different cutting strategies.

Small changes in depth of cut, stepover, or toolpath strategy can sometimes make a significant difference in machining time.

However, don't sacrifice workpiece quality, machine reliability, or safe operating limits simply to shorten a job.

Make Your CNC a More Useful Workshop Tool

A CNC router can do much more than cut decorative signs or shapes.

With the right tooling and techniques, it can create precise furniture parts, cut joinery, rough out carvings, and machine materials beyond wood.

The key is understanding how the cutter interacts with the material and developing a reliable process for every job.

Start with suitable bits, test your cutting settings, check the setup carefully, and save what you learn.

And remember that CNC woodworking doesn't have to replace traditional craftsmanship. Often, the best results come from combining the precision of a CNC router with the skills and tools you already use.

For more CNC woodworking techniques, projects, and demonstrations, follow Chris Fitch's CNC Basecamp series from Woodsmith.

CNC Basecamp: Aluminum Milling Basics

Think your CNC router is only for cutting wood? With the right tooling, setup, and cutting techniques, some home-shop CNC machines can also mill aluminum.

Join Chris Fitch in CNC Basecamp as he explores the basics of machining aluminum, including cutter selection, feeds and speeds, and practical techniques for getting clean, accurate results.

WATCH CNC ALUMINUM MILLING → Take Your CNC Beyond Woodworking