Dado on TS?

[Reed Wells]

Does anyone have any jigs or tips on cross grain dados for 4' plywood. I have an excellent set of blades. My problem is doing it by myself, when the plywood is slightly cuped (most of the time), I can't put enough pressure on the center to get the full depth of the dado. I feel like a fool calling help in every time I build an armoire. Any advise would be appreciated, Reed

[Steve Clardy]

I guess you can't turn it over, due to the good side and bad side?
Router will do it.

[Cliff Rohrabacher]

Ideally you'd have a sliding table saw. (Ideally that is.) I haven't bought mine yet so I have to make do.
When cutting big sheets and especially dadoing I have found it helps to have an infeed & outfeed tables and a side support table. With ply that's a tad warped I pop a 50 pound bag of sand on it and slide it that way. The infeed outfeed and support tables make my job simply to push and guide. When the pass is done the sheet is just sitting n the outfeed and I can take the bag off.
The outfeed table Sometimes it can take two people one to push and one to guide.

Note: Used pillow cases are great for keeping stray sand from getting around.

[Doug Shepard]

I'm guessing this might be for the back panel since it's 4' ?? If so could you screw some temporary stiffener strips of hardwood or MDF to it? The screw holes would only be visible from the back.

[Kelly C. Hanna]

I no longer do dados on the TS...I use my router and a sled I built for it. Much easier to maintain depth and no gymnastics required!

[Gary Swart]

Reed, me thinks you are not using a very good grade of plywood if it doesn't lay flat. You could use a router and follow the cupping in the plywood, but then what? The piece is still cupped and the piece you are sliding into the dado will be straight and not follow the cupping.

[Justin Nelson]

Reed,

I found this picture and it might be of use to you.

http://www.true32.com/WSWrapper.jsp?mypage=Groover.htm

Notice on top of the fence is two wheels mounted on it that hold the piece down and to the fence. They are known as "board buddies", they are directional so be sure to get the right colors. In your case you would want the yellow ones. Hope that helps :)

Justin

[Mike Cutler]

Reed.
I would use a router with the correct straight cut plywood bit, and a straight edge.
You end up between plywood thicknesses with a standard dado set, and have to reposition the fence to remove the final 32nd. The router is much easier, and more accurate.

[Norman Hitt]

Reed.
I would use a router with the correct straight cut plywood bit, and a straight edge.
You end up between plywood thicknesses with a standard dado set, and have to reposition the fence to remove the final 32nd. The router is much easier, and more accurate.

You don't with either of my Dado sets, you just have to use the right shims to get the correct dado width. Now the HOLD DOWN on warped PLY is another story altogether.:( I can buy the straightest/flattest ply there is, (not cheap stuff either), and take all the proper precautions with it, and it still warps. The stuff we get now sure isn't like it used to be. The old construction grade ply stayed flatter than the hardwood AND even Baltic Birch ply that I get anymore.:mad:

[Mike Cutler]

You don't with either of my Dado sets, you just have to use the right shims to get the correct dado width.

Norman.

Who makes your dado set?, and does it leave the little "ears" at the corners?
I have an old Freud dado set that I'm looking to replace, or at least get reground so that it doesn't leave those little "ears".

TIA. Mike

[Kelly C. Hanna]

No such thing as flat ply anymore around here. Once the dado is finished and the shelves installed any cupping is eliminated. Warping is another story, but I haven't found that to be an issue with my casework.

I can pick out the flattest ply in the metroplex and the minute you free it from the stack, you see the cupping and warping. It's just not made well these days. The more expensive you go you would think that wouldn't be an issue, but it is. Sad but true.

[Joe Chritz]

While cutting all dados on a TS is faster when you have lots to do for anything wide I now use a router and a simple two piece jig.

A piece of hardboard about 6 inches wide with a plywood piece glued/screwed on top. Chuck up a 3/8 straight bit and run it down the plywood edge. When the hardboard gets trimmed you now have the exact edge of your dado. Make two and place one on the layout line and clamp. A scrap piece of the material to go in the dado and position the other one and clamp. Only leaves one adjustment to mess up since the router can't leave the channel made by the jigs. Just mark your base and keep the same point against the jig face.

It's not an answer to your question but it is a solution and in practice is much easier than it sounds. It does require a decent work table for clamping. It's built from scrap so it's worth a try.

Joe

[Ed Bamba]

Does anyone have any jigs or tips on cross grain dados for 4' plywood. I have an excellent set of blades. My problem is doing it by myself, when the plywood is slightly cuped (most of the time), I can't put enough pressure on the center to get the full depth of the dado. I feel like a fool calling help in every time I build an armoire. Any advise would be appreciated, Reed

I'm not sure if this will work since you are trying to dado the concaved side of the cup using your TS (if I'm reading your post correctly). I read in either Kelly Mehr or Jim Tolpins TS book that a TS insert for use with a dado blade should have a slight hump in it. This is to counteract the convex profile of the piece you are dadoing. I don't think it mentioned how much of a hump is necessary, but it probably needs to be at top dead center of the blade. I haven't tried it since I don't have a dado blade, so I can't opine on the effectiveness of this idea.

Take care,
Ed

[Reed Wells]

Thanks ever so much, Problem submitted and solved thanks to you all. Ed B. I tried your table insert idea and it worked like a charm. I shaped it on my pump sander. Great ideas all, Thank you, Reed

[Ed Bamba]

Thanks ever so much, Problem submitted and solved thanks to you all. Ed B. I tried your table insert idea and it worked like a charm. I shaped it on my pump sander. Great ideas all, Thank you, Reed

Reed, I'm glad it worked out for you but I can't take credit for the idea. Like I said it was in one of the two books I mentioned earlier. There are other great ideas, procedures and jigs in those books, you may want to check them out. I found them in the County library. I do plan to purchase them one of these days though.

Take care, Ed

[Charlie Plesums]

Ideally you'd have a sliding table saw. (Ideally that is.) ....

I do have a sliding table saw, and mine does support dado blades (many do not). But I make my dados with a router, rather than fighting the warp of the panels.

I do have a 23/32 inch router bit, but I still often have to make two passes (I have gotten very good at it, since plywood thickness varies). Would you believe that I even got a batch of plywood recently that was 3/4 inch thick? 0.749 to 0.751 inches? I didn't think they even made real 3/4 inch plywood any more.

[Gary Keedwell]

http://www.newwoodworker.com/reviews/graphics/photos/tools/acurateguidervu/acurtguidevidfrm.jpg (http://www.newwoodworker.com/reviews/graphics/photos/tools/acurateguidervu/acurateguidedemo.wmv) Click on picture for new fixture Demo;)

[Rob Blaustein]

Would you believe that I even got a batch of plywood recently that was 3/4 inch thick? 0.749 to 0.751 inches? I didn't think they even made real 3/4 inch plywood any more.

Interesing--I've been using birch veneered ply lately from Home Depot--it's from Norwood Industries, or something like that, and it too really is 3/4".

[Scott Vigder]

Real 3/4" ply......cannot find anywhere........does not compute.....brain ready to implode.....