Dados in Walnut Plywood - Suggestions???

[james bell]

Any suggestions about dados in walnut veneer plywood? I am inserting the same plywood as shelves.

1) Should I use a dado blade on my TS - have a fair dado blade, not top of the line? If this is the answer, maybe I will need to upgrade to a better blade - the forest or freud, both of which got good reviews.

2) Use a router? In the past I have used a 5/8" bit with two passes. For a large number I will probably purchase a plywood bit ("assume" they are sized for veneered plywood).

3) Use a circular saw (festool) to cut the edges to prevent chipping prior to either option 1) or option 2), thus allowing me to use what I have. But many many passes, which in my experience just gives me a lot more opportunity to screw up somewhere!

4) Or any other solutions?

Thanks ... jim

[Greg Portland]

Assuming you have a stacked dado set (not a wobble blade) then it should work fine. To eliminate chip out be sure to use a zero clearance insert for that blade width -or- a crosscut sled w. zero blade clearance.

[glenn bradley]

+1 on the dado stack if it cuts clean. If you get unacceptable results a downcut spiral bit in your router and a couple passes (http://www.sawmillcreek.org/showthread.php?t=103755) would do the trick.

[Erik Christensen]

make sure all your dado's are with the grain - when I have tried to cut cross grain dado's even with a top line stacked dado set from CMT or RidgeCarbide the tear out along the whole edge was horrible.

[Chip Lindley]

As Glenn suggested, I believe I would use the router with a good upcut bit. Make a router jig to cut the slots at an exact 90deg. The bit can be referenced from the edge of the router base, or from a rub collar in the base. An accurage jig insures the bit will cut precisely where you want it. With a router, you can *stop* the dado at the front of the piece, rather than expose the shelf edge.

If the TS is your only means of cutting dados cross-grain to mount bookcase shelves, a very accurate/large sled will be needed. I'm not keen on cutting cross-grain dados *face-down* in this manner. Good clamping is required! One slight bobble and you've wasted some very nice walnut plywood.

Add: the edges of cross-grain dados can be scored or taped to minimize tearout. The freud SD508 gives great results! Even a used set I bought cuts solids and plys across the grain just Great!

[Darrin Davis]

Get a dado set with -12 degree hook on the teeth. I don't have any tearout across the grain of any playwood. (walnut, red oak, ash, mahogany, poplar....I've tried them all) I have the frued set and refuse to try anything different. You can't improve on perfect!

[David Prince]

Layout where your dados are going to be cut on the plywood and score the two edges with a utility knife. This will eliminate any tearout even if you use a wobble blade.

[Karl Brogger]

You want a dado head with a negative hook, not a positive hook. Even then its not a guaranteed cleen cut. I've got FS Tool dado heads, and a Forrest. The FS Tool ones do not do a good job cross cutting in veneer, while the Forrest does.

Regardless the easiest way to score the plywood is to do it with the dado head itself. I drag most parts backwards over the top of the dado head while running to score it, then push it through like I normally would. Its scary the first few times you do it, but once you get used to it you're only adding a couple of seconds to each dado. If you're squeemish about doing it that way, you can just make a pass with the head barely sticking out of the table, but then you have to adjust the height every time you have to cut a different piece.

[Kent A Bathurst]

+1 on tape advice - the wonderous blue masking tape. I have no problems cutting cross-grain dadoes on on my TS, but I use a Forrest stacked dado.

One other option - instead of a (nominal) full-width 3/4" dado, make it 5/8". The edges will be hidden. This means you need to rabbet your shelves by 1/16" on each face - make this with an initial cut using your best TS blade, then hog off the rest of the rabbet using dado set.

I'm not much of a router guy, so my advice is not a contradiction to the router responders.

[Joe Scharle]

I prefer the router with a jig like this. I've cut dados in walnut, oak, birch and even Chinese ply with no tearout using a 1/2" downcut spiral bit.

http://www.ncwoodworker.net/pp/data/194/Dado_Jig.JPG

[james bell]

decided against a dado blade for two reasons - 1) trying to keep it balanced and straight on my table saw (was cutting across a 2' x 8' piece and then ripping in half to ensure the dado's lined up; and 2) the cost of a good set compared with an undersized plywood bit.

purchased the whiteside, plywood bit used an All-in-One clamp as the guide, and did two passes - one very light to score the veneer and the second 3/8" deep. No problems at all. I did secure the clamp with extra irwin quik-grips to ensure my guide did not wander. Now I just need to wait for warmer weather to finish prior to glueing together and installing. shop isn't heated and global warming hasn't come yet - at least to my neck of the woods this winter.

many thanks for all of the input (and hopefully another project will force me to spend the money on a decent dado blade set.

[Walt Pater]

Nice looking router jig, Joe. I was going to suggest the same.