Spiral undersized dado bit?

[Michael Fink]

Does anyone make a spiral cutter that's undersized for plywood dados? I can't seem to find one, I have a plywood dado bit, but man, after using a spiral cutter, I'd love to have that for my dados!

[Rod Sheridan]

Hi Michael, plywood is metric in thickness, perhaps a metric bit is available?

The other issue seems to the variation in thickness between sheets.

Plywood is sanded after laminating and there's a tolerance allowed on the thickness........Regards, Rod.

[glenn bradley]

I too have found undersized questionable. The variations in plywood thickness between runs and (in the lower grades) even on the same sheet make them only partially useful. A metric spiral may be your answer. I have moved to using a smaller bit and a jig (https://sawmillcreek.org/showthread.php?262024-Auto-Width-Dado-Jig-Version-2&highlight=) to control actual width. This gets me the exact width every time (unless the thickness varies over the length :o).

[Bill Dufour]

Hunt ebay for a resharpened endmill. How much under do you need?
Bill D

[Martin Wasner]

Hi Michael, plywood is metric in thickness,

It's awfully thick if it's metric. The Russian plywood is, but domestic isn't that I've encountered.

[Brian Holcombe]

Working with the Russian plywood is a lot easier with standard tooling if you're putting veneers on it. If you have .710" plywood and put two .025" veneers on it, then you have .750" once you finish work the veneers. Of course I shop saw my veneers, so mine ends up around 7/8" thick once its finish worked.

I occasionally use it without veneering but pretty rarely, when I do I need to work with multiple passes to get a tight fit.