Router Bit Shank Size Comparison

Router bit shank sizes determine compatibility with router collets and affect bit rigidity. Larger shanks provide better stability for demanding cuts.

North American Standard Sizes

The 1/4 inch and 1/2 inch shanks are standard in North America. Most full-size routers accept both sizes with appropriate collets. Trim routers typically accept only 1/4 inch shanks.

European Sizes

European routers commonly use metric shank sizes: 6mm, 8mm, and 12mm. These are not interchangeable with inch sizes. A 6mm bit will not fit properly in a 1/4 inch collet despite similar dimensions.

Collet Requirements

Bits must match the collet exactly. Using an undersized bit in a collet is dangerous and can cause bit ejection. Never use adapters or sleeves that were not designed by the router manufacturer.

Selection Guidelines

Use 1/2 inch shank bits when available for large-diameter bits and heavy cuts. Use 1/4 inch shank bits for trim work, detail cuts, and when using trim routers. Match shank size to the demands of the cut.