1/4-inch or 6 mm router shank: match the installed collet

Match the shank to the collet

Trend’s guidance explicitly distinguishes 6 mm from 1/4 inch and requires the cutter shank to match the installed collet. Do not treat a rounded metric description as an equivalent imperial size. A listing that says only “quarter-inch compatible” needs a clear shank specification before it belongs on your shortlist.

The shank is the portion held by the collet. The cutting diameter is a separate dimension. A cutter advertised with a 6 mm cutting diameter could have a different shank diameter, so read the field labelled shank instead of using the largest number in the title.

Check what is fitted, not just what is supported

A router’s supported collet sizes and the collet supplied in a particular kit can differ. Bosch lists 6 mm, 8 mm and 1/4 inch as compatible collet diameters for the GKF 18V-8, while its UK variant includes the 1/4-inch collet-and-nut assembly 2 608 570 142. That does not make the included collet accept all three shank sizes.

Use the tool’s exact UK variant and the identification on the fitted assembly to establish what you have. If that is unclear, use the manufacturer’s parts information or support service before buying a cutter or replacement collet.

A collet size is not a universal replacement code

Bosch’s UK GKF 600 page lists a 1/4-inch collet with nut under part 2 608 570 135. The GKF 18V-8 example uses a different part number for the same nominal shank size. These listings show why “Bosch 1/4-inch collet” is an incomplete replacement-part request.

Save the manufacturer assembly code alongside the router model. Check whether the offer includes a collet, nut or complete assembly. Do not assume that a separate nut or another model’s collet can be combined simply because the size description matches.

Finish the cutter checks

Once the shank matches, check the cutting profile, cutting diameter, length, intended material and permitted application. Trend also requires observing the cutter’s maximum speed and the router’s fitting instructions. The shank check is one part of the buying decision; it does not establish that every cutter of that shank size is suitable for the router or job.