How do you cut Dado's for 1/4" Ply.?

[Stephen Dixon]

I need to cut several dados for 1/4" plywood. My plywood is so thin that even the undersize plywood routerbits are too big. I normally use a full kerf sawblade and move the fence to adjust the width, but in this case I need to make multiple indexed cuts for shelf dividers. I am thinking of using a couple of thin kerf blades together and adjust them with the shims from my dado set. What would you do?

Thanks Steve

[Mike Vermeil]

Steve,

You could make multiple passes with a 1/8" router bit, or modify a cheap steel 1/4" straight cutting bit to cut the width you want. If you work carefully with a bench grinder & maybe a stationary sander, you should be able to take a 1/4" bit down to the final size & get decent results.

Mike

[Jeff Sudmeier]

In this case, I would build a straight edge with fences on both sides, to cut the perfectly sized dado, with an 1/8" bit in two passes.

[Doug Cowan]

I just got a bit for 1/4" undersized plywood from LV and it worked great. If you have a caliper, you might want to check the thickness of the plywood and see if somebody like Lee Valley or Routerbits.com makes a bit that diameter. Personnally I would be a little gun shy about modifying a routerbit, and I would be surpised if the two saw blades turned out to be the right width. Another possible solution would be to try a shim along your table saw fence. Make your cuts with the shim, then pull the sim out and make the second pass. Good luck with it.