9 mm router bits

[Ruperto Mendiones]

I am a hobbist woodworker. Recently I have been making boxes of 9 mm plywood.

While I can make tight fitting dados with my dado stack, there are many times I would prefer to use my router table. Has anyone else encountered this need? Has anyone found a bit 8.xxx mm bits that fit 9 mm [nominal] plywood?

[Ronald Blue]

I googled 8 mm router bits and came up with several matches. Whether they are what you are seeking I don't know. Amana has one but it's also an 8mm shank.

[Jacques Gagnon]

Ruperto,

Have you tried using a micro adjustment mechanism on your router table fence? This allows me to dial in exactly the width required, even when a rabbet is involved. The combination of a properly sized spacer and fixed « bump stop » allows for processing of multiple parts.

I find that while the dado on the table saw produces the cut in one pass, the router table is a good option when dealing with smaller components.

Regards,

Jacques

[Bill Dufour]

Have a 9mm bit sharpened and it will lose some diameter. Or buy some 9mm endmills that are resharps. Do you have a 9mm collet?
Bill D

[mike stenson]

I have never seen any plywood that is reliably the same thickness.

[Mark Wedel]

11/32 is fairly close to 9 mm (8.73mm), so that might also work.

[glenn bradley]

Experience has taught me that "plywood" sized bits are often not. The bits are fine; it is the ply that varies too much. Multiple passes with a 1/4" bit gives me better results over time. These things (shop made or not) are now quite pricey but, back when I bought mine . . . not so much. It is a common fixture when I am working at the router table.

[Jim Becker]

"Best practice" when you are using tooling that cannot have the width varied in a granular way for grooving to take plywood is a multipass with a smaller tool so you can zero into the exact thickness dimension of the plywood. As has been mentioned, plywood thickness varies a surprising amount. And that's even in the same lot, simply because of how it's made. BB as well as premium products tend to have less variability, but it's still there. So-called "plywood thickness" tooling (router bits) are almost never going to be the exact thickness of the material being used.

[George Yetka]

best bet is a dado stack. Seconded by 2 passes with an undersized bit.

[Richard Coers]

A 5/16 router bit is .3125 or 7.94mm. Any grind shop can grind a 9mm bit down as mentioned. Second fix is to cut a rabbet on the plywood edge so it will fit in a 5/16" or 1/4" slot. Third option. https://www.youtube.com/watch?v=ctvMBq4nK5Q