Help, need advice on cross grain datoing

["Terry Pless"]

Hi, I'm building a couple walnut laminated 3/4" ply. display cabinets for a friend and I've had great success at cross grain dato cutting on 16" wide material using a sacrificial piece of wood on my radial arm saw but now if possible I need to cross grain dato cut on 8 pieces of 36" wide material. I have a jet 10" table saw with 2, 4'x8' tables attached to help support the sheets. Any advice or suggestions would be greatly appreciated.

[John Coloccia]

Can you use a router?

[Jerome Hanby]

+1 on using a router.


Can you use a router?

[Brian Tymchak]

How long are the pieces?

["Terry Pless"]

thanks for the response , router, had not thought about that, and they are 7' long or tall as they will be assembled. I haven't had great success with my router (with or without the table) using it for edges on wooden plaques, I most definitely could use some schooling on getting better results.

[glenn bradley]

+1 on the router. The small router base will follow the decidedly non-straight path of the plywood better than running that much length across a tablesaw thereby giving more uniform results. I know some tablesaw books promote the use of a ZCI with a hump built in to make the depth consistent on longer runs via a dado stack.

[Forrest Bonner]

another +1 on router. Try The Wood Whisperer website for a neat dado jig that sounds like it was designed for you.
http://thewoodwhisperer.com/exact-width-dado-jig/
Forrest

[Kent A Bathurst]

Sorry...late to the game. I was out of town, at a friend's house, fulfilling a [way-too-] long-standing promise for a built-in cabinet and shoe/boot shelves in their mud room.

The "pigeonhole" shelves are 3/4" & 1/2" ply, 24" x 6'+ tall, and since he doesn't have a full-blown shop I was cutting the shelves' dados with a router [MAN, did I miss my stuff!! - circ saw, jig saw and router, versus bandsaw and table saw with dado stack :(] . Here is my almost-foolproof method: [the only fool in the equation?? "C'est moi, c'est moi, I proudly proclaim.........." for you fans of Broadway musicals]

I had him buy a few sections of this stuff, in various lengths, to make alignment bars for his circ saw, and there was an extra piece laying around, so I made one for the router as well. 3/8" thick x 1-1/2" wide aluminum bar stock: http://www.grainger.com/Grainger/Flat-Stock-2EZE3. You cannot kill this stuff without serious abuse; it is flat and straight, and has a very low profile to allow clearance for tools' handles and motors.

Drilled and tapped some 1/4" holes in it [yes - I had him buy a modest tap & die set at the local Ace]. Used machine screws through 1/4" plywood with countersunk holes to mount the bar stock. Ply started out at "too wide" - prolly 10" - 12" or so - just grabbed a chunk he had laying around. Then, use the router [with the bit to be used on the dados - in this case, 5/16"] to run down one side of the bar stock and cut the ply to the exact offset location.

Then, working down the verticals, simply make pencil marks for layout. Align the cut edge of the ply to the layout marks, clamp it to the workpiece and table, and the router will cut exactly where the dado needs to be. I always messed before up with a simple piece of wood as a guide, and doing the math to offset for the router and the tenon shoulder, and then I'd end up in situations where the circ saw motor wouldn't clear the guide.......... The jig [~30" long, with 5 tapped holes] took maybe 30 minutes to make. The cut side is only accurate for that specific router [I took one of mine - I hate his] with that specific bit, but the other side [where I place the clamps] is still "too long" and can be made to work with any other setup or tool. Plus - the time was in the drill and tap step - the 1/4" ply can be tossed and replaced quickly.

Previously, I had made him a 96" version for the Sawboss circ saw - with the bar stock overhanging the ends by 6", to allow for a clean start. And also a shorter version of that one for circ saw on smaller stuff.

For this type of work, the accuracy of this method is excellent - nice clean layout marks and pay attention to the jig alignment, and I'm easily accurate within the width of a pencil mark. Not nearly as cool-looking as a Greenstuff EQ Plunge saw & track, plus router and track adapter, but hey...........I want him to spend his money on beer and wine for my visits, not Kool-aid :D

[Trent Shirley]

You could do this on the table saw or with the router but the router would probably be the easiest to manage with less tearout. Build the jig that Forest Bonner mentions in his reply, this makes setup of your dado very quick and accurate and it also helps you to avoid any tearout of the material on the top of the board since the jig itself will be covering that edge.
You would be well advised to leave the piece long in case you get any tearout on the ends of the boards or back the boards up with extra material so the router does not cause tearout when it reaches the end.

You are generally better off making your cut in two passes so you do not cut too deeply all at once which can lead to tearout and burning of the material. If the width of the dado you need is greater than the size router bit you have there is no problem you just cut the back side of the dado moving from left to right then cut the front of the dado moving right to left. It will make more sense once you see the design and demonstration for the router dado jig. The reason for left to right along the back then right to left along the front is to keep your router bit almost moving with the bite of the bit into the material.
The router dado jig will clamp down to your material but you should make sure the material is clamped down as well or it will want to move on you as you cut your dado.

Use the router dado jig

Hi, I'm building a couple walnut laminated 3/4" ply. display cabinets for a friend and I've had great success at cross grain dato cutting on 16" wide material using a sacrificial piece of wood on my radial arm saw but now if possible I need to cross grain dato cut on 8 pieces of 36" wide material. I have a jet 10" table saw with 2, 4'x8' tables attached to help support the sheets. Any advice or suggestions would be greatly appreciated.

[Myk Rian]

When using the router, the first stroke should be a very thin cut to break the edges. It helps prevent tearout when making the deeper, final cut of the dado.

["Terry Pless"]

Hey Guys, Thanks for all the help. I did the job using the router (whent and bought a new one) and did as advised with two pass's and it came out great, when I get these done I'll post some pic's. thanks again for everybody's response it helped a ton. Terry