How to Set Up and Use a Multi-Radius Router Bit

Quick answer

To set up a multi-radius router bit, install the desired bearing for the radius you want, set the bit height using a test cut, and match the shank size to your router collet. Always unplug the router before changing bits or bearings, and make a test cut on scrap wood to confirm the profile before routing your final piece.

Choose the right shank size for your router

Router bit shank sizes must match your router collet. Common sizes are 1/4-inch and 1/2-inch. A 1/2-inch shank provides more stability and is preferred for larger bits and deeper cuts, while 1/4-inch shanks fit smaller routers and trim routers. Never force a bit into a collet that is the wrong size. If your router accepts both sizes, use a reducer sleeve only if it is designed for your specific collet. Check your router manual for the maximum shank size and recommended bit diameter.

Understand how a multi-radius bit and bearing kit work

A multi-radius router bit uses interchangeable bearings to change the cutting radius without changing the bit. The bearing rides against the workpiece or fence, controlling the depth of cut and the profile shape. By swapping bearings, you can rout different roundovers, coves, or decorative profiles with one bit. This is especially useful when you want to create custom moldings or edge treatments without buying multiple bits. Always ensure the bearing is the correct size for the profile you intend to cut and that it spins freely.

Install the bearing and set the bit height

Before installing the bit, unplug the router. Select the bearing that matches your desired radius and slide it onto the bit's bearing post, securing it with the included screw or clip. Hand-tighten only; over-tightening can damage the bearing. Insert the bit into the collet, leaving about 1/8 inch of the shank exposed below the collet nut, then tighten the collet properly. Set the bit height by adjusting the router's depth mechanism. For edge-forming cuts, the bearing should contact the workpiece edge; for plunge cuts, set the depth to the desired profile depth. Always make a test cut on scrap wood to fine-tune the height.

Set up your router table or fence for safe routing

When using a router table, adjust the fence so the bearing rides against it or against the workpiece edge, depending on the cut. For edge profiles, the workpiece should be guided along the fence with the bearing contacting the edge. For plunge cuts, such as rosettes, you may need to use a starting pin or a template. Ensure the fence is parallel to the miter slot and that the bit guard is in place. Feed the workpiece against the rotation of the bit (from right to left) at a steady pace. Do not force the cut; let the bit do the work.

Make a test cut and check the profile

Test cuts are non-negotiable. Use a piece of scrap wood that matches your final workpiece in thickness and species. Run the cut with the same feed rate and direction you plan to use. Inspect the profile for burn marks, tear-out, or an uneven radius. If the profile is too deep or too shallow, adjust the bit height or switch to a different bearing. If the cut is rough, try a slower feed rate or take multiple passes. Once you are satisfied, proceed to your final piece.

Common mistakes to avoid

One frequent mistake is using the wrong bearing size for the desired radius, which results in an incorrect profile. Another is routing in the wrong direction, causing kickback or tear-out. Always feed against the bit rotation. Over-tightening the collet can damage the bit shank or collet, so tighten firmly but not excessively. Finally, do not bottom out the bit shank in the collet; leave a small gap to allow proper tightening.

Step-by-step setup

1. Unplug the router and select the bearing: Choose the bearing that matches the radius you want. For a multi-radius bit, the bearing size determines the cutting depth and profile. Ensure the bearing spins freely. Checkpoint: Bearing should rotate without wobble.
2. Install the bit and set the height: Insert the bit into the collet, leaving about 1/8 inch of shank exposed, and tighten the collet nut firmly. Adjust the router's depth so the bearing rides against the workpiece edge or fence as needed. Checkpoint: Bit is secure and height is set for a test cut.
3. Make a test cut on scrap wood: Run the cut with the same feed direction and speed you plan to use. Inspect the profile for accuracy and finish. Adjust height or bearing if needed. Checkpoint: Profile matches your intent and cut is clean.
4. Rout the final piece with steady feed: Feed the workpiece against the bit rotation at a consistent rate. Avoid stopping or forcing the cut. Use push blocks or a featherboard for safety. Checkpoint: Smooth cut without burn marks or tear-out.

Product facts

• Infinity Tools 1/2" Shank Multi-Radius Router Bit w/ 3-Pc. Bearing Kit: Infinity Tools 1/2" Shank Multi-Radius Router Bit w/ 3-Pc. Bearing Kit includes three 3/16" I.D. bearings for creating multiple radii without changing bits. This kit lets you switch between three popular radii quickly, saving time and cost compared to buying separate bits.
• Infinity Tools 1/2" Shank Ovolo Router Bits w/ Bearing: Infinity Tools 1/2" Shank Ovolo Router Bits w/ Bearing cuts six different profiles and is designed to plunge directly into your workpiece. Its plunge capability and six-profile versatility make it useful for decorative details like rosettes and custom moldings.
• Infinity Tools 1/4" Shank, 3/8" Cutter Radius, 1/2" Cutter Height Cove Router Bit: Infinity Tools 1/4" Shank, 3/8" Cutter Radius, 1/2" Cutter Height Cove Router Bit features a 1/4" shank and is designed for concave detailing on furniture, cabinet doors, and molding. This bit is a good choice for smaller routers and precise edge profiles where a 1/4-inch shank is required.