Replies

1. 
   DougF | Apr 18, 2005 04:33pm | #1

   There are couple of ways to deal with this problem.  The first is fairly obvious, shim the dado slot.  Since most ply vary in thickness, I would suggest that you under cut the dado slot using a 5/8" dado bit and then rabbet the plywood to match the slot. 

   Doug

2. 
   jackplane | Apr 18, 2005 05:08pm | #2

   A second suggestion requires a deft touch. Reverse the polarity on your router, then mount in a table. With the machine on, apply a honing stone to remove a fraction of material until with dial calipers the bit diameter is correct. Use eye and respiratory protection.

    

1. 
   Sancho | Apr 18, 2005 05:39pm | #3

   Couple of options here ,

   Just pick up a cheap set of bits from woodline (great bits, cheap but good) or

   buy one 3/8 to 1/2 bit from woodline and cut then move the fence and cut again...

   But

   personally, id spend the 20 bucks on a set from woodline Buck Construction  View Image

      Artistry in Carpentry

           Pgh, PA

1. 
   jackhall | Apr 18, 2005 10:27pm | #7

   I have been wondering about how to route dados for plywood that may vary in thinkness.  I was thinking of building one of those adjustable parallelogram jigs that can be set at any width, then clamped to the board and serve as a fence for the router.  I had a basic question though.  When setting up fences for routing slots, is it better to guide on the router baseplate, a collar around the bit, or use a bit that has a roller bearing to guide it?

1. 
   nikkiwood | Apr 19, 2005 01:12am | #8

   I never cut a full size dado to fit a piece of ply -- for all the reasons mentioned above. I generally cut a dado at 1/4" -- either with a TS dado or a router -- and then rabbet the ply to fit.For routering, to keep things quick and easy, I use one of those flat, guide clamps. To measure the distance from the guide clamp to the router cut, I have made up two different boards (one for a 1/4" cut, the other for a 1/2", both made from 1/4" luan ply). All I have to do is mark where I want the edge of the router cut to be, lay down my jig board, square it up, slide the guide clamp up to it, and tighten it down. I also have made up some shooting boards which I occasionally use for router cuts."I would never die for my beliefs because I might be wrong."
   -- Bertrand Russell

1. 
   dinothecarpenter | Apr 19, 2005 04:18am | #10

   Nice technique.

   The Other Ez way is the smart router kit. Instead reposition the "shooting board"

   The sliding arm moves in and out. As long as you position the "shooting board" parallel to your desire dado or whatever, the rest is under control.

    View Image 

   Edited 4/18/2005 9:27 pm ET by YCFriend

   Edited 4/18/2005 9:28 pm ET by YCFriend

2. 
   forestgirl | Apr 19, 2005 04:39am | #11

   I think a link should be provided:

   http://www.eurekazone.com/products/ezsmartrouter.html

   Eurekazone, Inc.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the  "I Rocked With ToolDoc Club" .... :>) 

3. 
   Len | Apr 18, 2005 05:44pm | #4

   It's possible that you have 17mm thick plywood rather than 3/4. It seems to be the norm today.  I your going to a lot of dadoes in plywood then it might be worth investing in the 17mm bit.

   Otherwise you can make a jig using a bushing and a 1/2 or 5/8 diameter bit. Rip a couple of 4 to 6 inch strips of plywood (or MDF). Attach a another strip to the end of one at a right angle. I like to use that piece to square it against the stock. Pick your bushing/collar size. (Say 3/4 diameter for a 1/2 diameter bit) Run the router into the cross piece. That will be your one edge. Mark your thickness on the cross piece and account for the difference between the bushing and bit. Mount the other strip to the cross piece and another cross piece at the other end. Voila.

   Hope this helps.

   Hi, I'm Len and I'm a Toolaholic...
4. 
   BG | Apr 18, 2005 05:53pm | #5

   Toolfreak,
   One other option: use a 1/2" router bit for the dado and put a 1/4" rabbit on the underside of you ply shelf..adds strength too and puts you back in control.
   I've used the special sized 3/4" bit and have found the thickness of the ply to vary.

   
   

   ---

   Edited 4/18/2005 10:56 am ET by BG

5. 
   Yogi | Apr 18, 2005 06:12pm | #6

   Maybe an adjustable dado blade for your t/s?

6. 
   ASK | Apr 19, 2005 01:15am | #9

   Toolfreak,

   I spent this last weekend cutting dados and rabbets for kitchen cabinets for my kids on the table saw with a dado blade. Had to do a lot of test cuts to get the right width with shims but everything worked out well.

   ASK

7. 
   bladeburner | Apr 19, 2005 03:48pm | #12

   Build this jig from Shopnotes:

   View Image

   They even have an online video showing it in action. I built it and it is sweet. The guides self-align for the thickness you're actually using. So it doesn't matter how thick or thin the material is.

   Joe

1. 
   DougF | Apr 19, 2005 05:03pm | #14

   Joe,

   What issue was the jig in? 

   Doug

1. 
   bladeburner | Apr 19, 2005 05:24pm | #15

   Just go here:

   http://www.shopnotes.com/main/sn76-toc.html

   Joe

1. 
   DougF | Apr 19, 2005 05:33pm | #16

   Joe,

   Thanks.  That issue is not listed in their back issue availability but I emailed them to inquire further. 

   Doug

1. 
   bladeburner | Apr 19, 2005 05:55pm | #17

   Email me :

   [email protected]

   Joe

2. 
   forestgirl | Apr 19, 2005 07:29pm | #18

   For those who want to search their own library, that router dado jig is in #76, July/August 2004.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the  "I Rocked With ToolDoc Club" .... :>) 

1. 
   DougF | Apr 19, 2005 08:25pm | #19

   Thanks Jamie.  I don't take ShopNotes but I'm trying to purchase a back edition.

   Doug

1. 
   forestgirl | Apr 19, 2005 09:13pm | #20

   Any time, Doug.  If I had a copy, I'd try and help you out, but last summer I let my subscription lapse.  Wish I hadn't, I could use that jig.  I'm there are other designs out there, but this one sounds like a good one!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the  "I Rocked With ToolDoc Club" .... :>) 

8. 
   Dave45 | Apr 19, 2005 04:11pm | #13

   Several years ago, I bought two straight cutting router bits for "undersized" plywood.  One is 23/32" and the other is 15/32".  If memory serves, I got them from MLCS (http://www.mlcswoodowrking.com).

1. 
   JohnSprung | Apr 20, 2005 03:31am | #21

   I got a set of three "plywood size" router bits at Rockler.  I had one of their discount cards, and was loading up on goodies that day.

    

   -- J.S.

    

9. 
   MiKro | Apr 20, 2005 10:11pm | #22

   http://www.grizzly.com/products/item.cfm?itemnumber=H5558

   Heres a plywood set of bits from grizzly $12.95