Need a back that will with stand racking

[Al Bacon]

I am building a case that will have a racking force at times. I can use a 3/8"plywood back or a frame of 3/4" with half lap joints and a 3/8 plywood panel glued in a rabbit in the back. The latter is what I would like to use but don't know if it would be as strong.
I would appreciate any feed back you guys could give on this.

Thanks

[Lee Schierer]

I think either format would resist most racking forces. The advantage of the frame and panel design is that you have a little more meat to join to the bottom, top and ends of your cabinet and your panel is glued in a U shaped groove.

[Al Bacon]

Thanks Lee

There is not an easy way to cut the grove in the rails and styles if the joints are half laps without the groves showing on the ends. I was thinking of a rabbit cut into the back of the frame after assembly and then gluing the plywood into the rabbit. Would this be weaker than the U shaped grove?

On second thought I guess I could cut the grove with the dado blade or on the router table if it is stronger.

[james klein]

I've done this with a horizontal slot-cutter with a bearing and chiseled the corners. You might consider running the rabbit a bit deep and running a bead of adhesive around the back to prevent any displacement where it's not wanted. Another thought is, if your not partial to the half lap joints, just do typical 5 piece shaker panel and back cut the 3/8 ply.

[Lee Schierer]

Thanks Lee

There is not an easy way to cut the grove in the rails and styles if the joints are half laps without the groves showing on the ends. I was thinking of a rabbit cut into the back of the frame after assembly and then gluing the plywood into the rabbit. Would this be weaker than the U shaped grove?

On second thought I guess I could cut the grove with the dado blade or on the router table if it is stronger.

I use lap joint construction as a frame fairly often. Cutting a groove that won't show if fairly easy with a horizontal slot cutting bit in a router and a fence. I mark the start point on my fence with masking tape and a pencil and also the stop point so that I get a full depth groove in the rectangle area of the frame (Some of the curved portion of the cut will be in the lap area). I adjust the width and depth of cut to what I want first. Then start the router and lay the piece to be cut flat on the table at an angle to the fence with the leading end near my start mark without contacting the bit and slowly rotate the piece into the cutter, keeping your hands behind the cutter. Once you have made the plunge cut, slide the piece along the table to the stop mark. Turn off the router, wait for it to stop and remove the piece.

[Al Bacon]

Thank you, Slot Cutter it is. When I stop to think of it that is the best and easiest way to accomplish it. :)