Jodee from Inspire Woodcraft shared the woodworking tip featured in this video.
Jodee explains why using the round side of a router sub base usually gives more consistent results when routing along a straight edge and how a simple centering adjustment can eliminate wandering cuts.
The video covers why the flat side can cause problems, three practical ways to center the sub base, and when the flat face is actually useful.
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Why the round side works
The round side of a router base keeps the cutting bit at a consistent distance from a straight edge because the circular perimeter maintains the same radius as the router is rotated.
This stability means you can twist or pivot the tool slightly during use without the bit creeping closer to or farther from your guide.
How to center your sub base
Centering the sub base to the bit is the key detail many people miss, and it’s the difference between predictable cuts and wandering joints. Jodee demonstrates several simple approaches to get your sub base aligned.
- Measure with a bearing-mounted bit: Install a router bit with a clean bearing and measure the distance from the bearing to multiple points around the round base, then loosen the sub base screws, shift the plate until measurements match, and re-tighten while checking for movement.
- Use a chamfer (or two-flute) bit as a gauge: With the chamfer bit installed, loosen the base screws and lower the plate until the base hole edges just touch the cutters all the way around, rotating the bit to confirm even contact before securing the plate.
- Switch to tapered screws: Replacing flat pan-head factory screws with tapered-head fasteners can help the sub base self-center into the router body holes, bringing the plate closer to true center with minimal fuss.
Tools and tolerance
Perfectly machined circles sound ideal, but in practice being close is usually good enough when you use the round side of the plate
There are also purpose-built centering cones and jigs available for those who want a faster or more repeatable way to center different routers and plates.
When the flat side is useful
The flat side of a base isn’t useless—many routers (especially plunge bases) include a flat face to brace against a straight edge and reduce rotation when plunging into material.
When the flat side is held firmly and consistently against a guide it can provide extra control, but it’s more sensitive to small twists if the sub base isn’t properly centered.
Practical advice and common pitfalls
Always re-check centering after tightening screws because the plate can shift under torque, and small adjustments make a big difference in edge work.
Treat the round side as the default for guided straight cuts and save the flat side for controlled plunge operations or delicate maneuvering where a stable reference surface is required.
Why this tip matters
Getting the sub base centered and preferring the round face for guided cuts removes a common source of frustration and improves repeatability in joinery and edge work.
The approach is adaptable to most routers and can be applied with simple tools and minimal time investment.
Support Jodee by visiting his online store here: https://inspirewoodcraft.com/collections/all.
Matt’s Take
These are my personal thoughts and tips based on my own experience in the shop. This section is not written, reviewed, or endorsed by the original creator of this project.
This centering tip is one of those fundamental router techniques that can transform your work once you dial it in. The difference between a properly centered sub base and one that’s even slightly off becomes obvious when you’re trying to make consistent dadoes or edge treatments. I’ve found that taking the extra few minutes to check centering before starting a project saves way more time than trying to fix wandering cuts later.
The bearing method Jodee demonstrates is particularly reliable because you’re essentially using the bit itself as your reference point. When using the chamfer bit technique, work slowly and check multiple spots around the circumference — router bases can be slightly out of round from the factory, so you want to find the best compromise position rather than chasing one perfect measurement.
Safety-wise, always unplug the router when making these adjustments, even though it seems obvious. Those bits are sharp enough to do damage even when the motor isn’t running. And remember that different bit diameters can reveal centering issues that smaller bits might hide, so it’s worth spot-checking your setup when switching to larger cutters.
The round-versus-flat debate really comes down to control and forgiveness. The round side gives you that buffer zone where small movements don’t immediately translate to cut variations, which is especially helpful on longer cuts where maintaining perfect pressure and angle gets tiring.