Making A Rabbet in 1/2' Baltic Birch Plywood Best Practice

[Roger Davis]

I am building a sanding downdraft box from 1/2" Baltic birch plywood and need to make 1/4"W x 1/2"H rabbets in the box sides to accept the bottom panel.

I have both a stackable and wobble dado blade for the table saw and a router table with both upspiral and regular straight bits of various sizes.

As I was planning the cut, I asked myself should I stand the side on edge and make rabbet or put the side on the face and make the rabbet.

What is the best practice to make this rabbet that would minimize tear out? Should the router bit or saw blade be parallel or perpendicular to the plywood plys?

Thanks,

Roger

[glenn bradley]

I score the face line with a razor knife. Use your stack and assemble it wide. Add a sacrificial fence to your tablesaw fence and bury the dado into it leaving the width you want exposed.

k-Ped-Table Dado 3.jpg

The example picture is, of course, not plywood but, you get the idea ;-)

[Bill Huber]

On plywood I agree with Glenn 100%, now if it was hardwood I would just use my router table and a rabbeting bit.

[Rod Sheridan]

Roger, best practise would be a shaper with a stock feeder and a rebate head.

Of the options you've listed, flat on the saw with a dado cutter would be my choice.

Note that with sheet goods you often have a warped sheet, make sure you press down hard on the material to flatten it....................Rod.

[Justin Coon]

When you're burying a dado stack in a sacrificial fence attached to your fence, is there a certain amount that you want to have buried? That is, is part of the idea to have one of the outer blades completely buried so you are cutting the rabbet with only one outside blade for the shoulder and the chippers for the remainder of the waste? On the same line of thought, do you need to have more than just the outside blade of the stack buried for optimum performance?

[John TenEyck]

For shop cabinets I wouldn't waste the effort to pre-score anything. I'd either cut them with two cuts using your standard TS blade through a ZCI, or with a stacked dado buried in a sacrificially fence, as described above.

John

[Huck Schwee]

Don't forget a backer board to reduce the tear-out on the backside of the plywood.

[Prashun Patel]

I'd just blue-tape the underside. Also, I wouldn't do rabbets in the sides; I'd make a groove so the bottom panel is fully supported.

[Alan Bienlein]

I would just use my dado set on the table saw.

As for scoring I don't understand why anyone does that as it's not necessary. If your dado set can't make a clean cut in plywood without a zci then you need a better dado set.

[Mark Wooden]

A router with a rabbetting bit will be easiest to get an even depth of cut. Best would be a shaper with a feed (like Rod said)because it would leave you with an even amount of material left on the sheet which is what you want to maintain dimension. If you use a tablesaw (most common method) use a good featherboard or such to hold the stock down tight to the table.

[Jim Barstow]

I just built 14 drawers and 4 cabinets all with rabbets. I made a first cut across the face of the plywood the depth of the rabbet with a good blade and ZCI. I then put a tall auxiliary fence on the table saw and cut the rest of the rabbet with the wood on edge. (The cabinets were 30"x30"x3/4 and it was easy to handle the wood. The drawers were all 1/2" Baltic birch and tedium was the only problem.)

The result was perfect with absolutely zero tearout. I don't even own a dado blade and I've been at this for 35 years.

[Roger Davis]

Thanks to all that provided great ideas. I set up a 5/8" diameter straight carbide router bit in my router table that has an Incra/Jessem Router Lift II, set the fence for a 1/2" width cut and 1/4" bit height and routed a clean rabbet in the Baltic birch plywood. Used a backer board to eliminate tear out. Joints are perfect.
Roger

[Peter Quinn]

Post mortum, for the base of a shop cabinet or utility fixture, I'd do whatever is quickest/easiest. Probably use whichever tool I could set up fastest at the time, which for me is usually the router table.