When using a router for planing wood, the bit you choose is an important decision that will impact the finish and quality of your work. There are a few key factors to consider when selecting a router bit for planing operations:
Page Contents
- 1 Straight vs Spiral
- 2 Diameter
- 3 Number of Flutes
- 4 Carbide Cutters
- 5 Feed Rate
- 6 Cut Depth
- 7 Grain Direction
- 8 Climb vs Conventional Cutting
- 9 Shank Size
- 10 Reduced Shank Bits
- 11 Chipbreakers
- 12 Feed Direction
- 13 Bit Length
- 14 Collets
- 15 Feed Direction Summary
- 16 Do a Test Cut First
- 17 Use a Jig
- 18 Pre-Drill Holes
- 19 Wear Eye and Ear Protection
- 20 Use Dust Collection
- 21 Conclusion
Straight vs Spiral
The two main types of router bits used for planing are straight bits and spiral bits. Straight bits have cutting edges arranged in a helix along the length of the cylinder. Spiral bits have one continuous cutting edge that wraps around the bit in a spiral pattern from top to bottom.
Spiral bits are ideal for planing because they produce very smooth, tear-out free cuts. The continuous cutting edge shears the wood fibers for a splinter-free finish even against the grain. Straight bits can sometimes cause more chipping and tear-out.
Diameter
Larger diameter bits 1/2″ or greater are preferred for surfacing and planing operations. The larger diameter provides a wider cut that removes more material in a single pass. This allows you to hog off wood efficiently while still taking light passes under 1/16″ for a smooth cut.
Number of Flutes
2 to 4 flute carbide tipped bits are common for router planing. 2 flute bits are most aggressive for fast material removal, while 3-4 flute bits leave a finer finish. 4 flute bits also provide more chip clearance when hogging off larger depths of material.
Carbide Cutters
Carbide cutter tips are highly recommended for router planing bits. Carbide remains sharper much longer than high-speed steel bits, providing more cuts between sharpenings. The carbide cutters shear the end grain cleanly for minimal tear-out.
Feed Rate
When planing with a router, use a slow, steady feed rate to achieve the best results. Roughing out heavy cuts quickly will likely cause chatter, burn marks and an uneven surface. For final light planing passes, slow down the feed rate to allow the carbide cutters to shear the wood cleanly.
Cut Depth
Make very light passes not exceeding 1/16″ depth of cut when planing wood with a router. Taking off too much material in one pass risks burn marks, tear-out, and an uneven surface. Roughing out thicker cuts up to 1/8” is acceptable when removing waste efficiently.
Grain Direction
Always plane or rout with the wood grain, not against it. Planing against the grain fibers causes splintering and chipping. If the workpiece edges are not oriented with the grain direction, start by edge jointing sides before planing the faces.
Climb vs Conventional Cutting
For planing, a conventional cut is recommended where the router bit rotation moves downward through the workpiece. Climb cutting pulls the router in the feed direction, increasing potential for tear-out. However, a light climb cut may be used for final smoothing pass.
Shank Size
Use a router bit with a shank size that matches your router collet. Common shank sizes are 1/4″ and 1/2″. Larger diameter cutters often require a 1/2″ shank to provide stability when hogging heavier cuts.
Reduced Shank Bits
Some spiral planing bits have a reduced shank under the cutter section allowing greater depth of cut. This helps maintain router power when removing thicker passes of material.
Chipbreakers
Chipbreaker grooves located above the cutting edges can help break up wood chips and improve chip ejection when planing thick stock removal with a router. This helps prevent clogging.
Feed Direction
For table-mounted or handheld routing, feed the workpiece from right to left. This helps prevent climbing and tear-out. Use a router table fence or edge guide to maintain a consistent feed direction.
Bit Length
Standard length 2-1/2″ to 3″ long bits allow sufficient cut depth for most edging and facing operations. For surfacing wider stock, use extended reach 4″ to 5″ router bits.
Collets
1/4″ and 1/2″ collets should be standard accessories with any router. Double check collet size matches the shank diameter of your chosen router bit before use.
Feed Direction Summary
Here is a summary of optimal feed directions when planing with a handheld or table mounted router:
| Operation | Bit Rotation | Feed Direction |
|---|---|---|
| Edge planing | Downcut | Right to left |
| Face planing | Downcut | Towards operator |
| Surfacing wide boards | Downcut | Right to left |
Do a Test Cut First
When switching to a different bit profile or wood type, always do a test cut on scrap first. Check for any signs of burning, tearing or chipping before moving on to cutting your final workpiece. Adjust feed rate and depth of cut as needed.
Use a Jig
For safety and accuracy, use some type of guide or jig when planing stock with a handheld router. Options include a straight edge guide, piloted planing jig or reducing sled to reference off a workpiece edge.
Pre-Drill Holes
If planing a workpiece that already has mounting holes drilled through it, take the time to pre-drill clearance starting holes. This prevents the chance of the router bit grabbing the edge of an existing hole, potentially causing kickback.
Wear Eye and Ear Protection
Always wear proper eye protection to prevent debris from being thrown by the spinning router bit into your eyes. Ear protection is also a must for reducing noise exposure when running a router for extended periods of time.
Use Dust Collection
Connect your router to a shop vacuum or dust collection system. Planing produces large quantities of wood chips and dust that can quickly build up without proper chip extraction.
Conclusion
When planing wood with a router, opt for a large diameter spiral upcut or downcut carbide bit. Take light passes of 1/16” or less with a slow feed rate to achieve a smooth surface. Always feed against or parallel to the wood grain to prevent splintering and tear-out. With the right technique and a quality router bit, you can achieve professional, splinter-free planing results.