5 Tips for Flush Trim Router Bits

5 handy tips for using flush trim router bits

Flush trim router bits are a game-changer when it comes to getting smooth, professional-looking edges. Whether you’re working on templates, trimming veneers, or cleaning up edges on a project, knowing a few tricks can make all the difference. In this guide, we’ll share five simple yet effective tips to help you get the best results with your flush trim bits.

Pick the Right type of Flush Trim Bit for the Job

Not all flush trim bits are the same, so choosing the right one is key! There are essentially 3 styles of flush cutting bits with bearings:

• Flush Trim Bits (also called bottom bearing) work best for a router table when your template sits on top of the material.
• Pattern / Template Bits (also called top bearing) are ideal for a hand router when the template is on top.
• Combination Flush Trim Bits (also called dual-bearing) gives you the choice to work from either direction.

Pick the right cut direction and shank diameter

There are several options to choose from, from the standard steel shank straight bit with brazed carbide cutters to solid carbide spiral bits. Keep in mind with spirals, cut direction is always in relation to the router itself.

• Straight Cut bits work in a scraping action across the edge of the board and can result in heavy tear out or chip out, especially around end grain corners.
• Up-cut bits are shearing upwards toward the router and are the best general purpose choice for flush trim bits. On a router table, up-cuts help pull the workpiece down towards the table, helping the cut be more stable.
• Down-Cut bits shear down and away from the router and are suited for trimming laminates or plywood when you absolutely need to have a crisp upper edge. Keep in mind that on a router table, down-cut bits can push the workpiece up and away from the router, potentially resulting in erratic behavior.
• Compression bits are essentially a hybrid; the tip is up-cut and the rest of the flutes are down-cut essentially shearing the fibers towards the middle of the workpiece.
• Shank diameter depends on the jobs you do; if you’re working on a small, one off project, a 1/4″ shank.

Take It Slow and Easy

Trying to remove too much material in one go can lead to tear-out, burn marks, or rough edges. Instead:

• Try to rough-cut away as much extra wood as possible with a jigsaw or other method.
• Take multiple light passes instead of one deep cut.
• Adjust your router speed; spiral bits are designed to cut efficiently at 16,000RPM (about mid-dial on most routers). This serves two purposes; it helps keep heat build up at a minimum, prolonging the life on the edge and it keeps the lubricant in the bearings from overheating, degrading and ruining the bearing (especially on ¼” bearings).

Pay Attention to Feed Direction

Moving your material in the right direction is super important for a clean cut and safety.

• Always try to cut with the grain to avoid tear-out.
• Conventional cutting is easier to control, while climb cutting can give you a smoother cut but takes more experience.
• Avoid starting a cut in end grain which can cause a kickback immediately (especially an inside cut in a charcuterie board handle).
• If you’re new to climb cutting, practice on some scrap wood first, and keep a firm grip on your router.

Keep Your Bits Sharp and Clean

Dull or dirty bits can lead to messy cuts and extra wear on your router. Here’s how to keep them in top shape:

• Clean off resin and dust buildup with bit cleaner or a simple household degreaser.
• Store your bits properly in a case or rack to keep them from getting damaged.
• Keeping your bits in good shape will make your cuts cleaner and help your tools last longer!

By choosing the right bit, taking light passes, using the correct feed direction, and keeping your bits sharp, you’ll get smoother cuts and better results every time. Try out these tips on your next project and see the difference!

Got a favorite trick for using flush trim bits? Drop a comment below and share your experience! And if you’re in need of some quality flush trim bits, check out what we’ve got