Cross lap joint shelving advice

[ear3]

I'm designing a wall mounted bookcase for some folks where, because of the space, it can't be enclosed with an outer frame/case, and has to be assembled on site. I thought a good solution would be to make it via cross lap joints. I've done mini versions of cross lapping for boxes and drawers, but never something of this scale (assembled shelving unit would be around 6 or 7ft tall, 5.5ft wide with an 8 or 9" depth, which I'm thinking could be done via three uprights and 6 horizontal shelves). Anyway, was wondering if there are any best practices (other than dead flat boards) on sizing the boards to the groove, which leaves enough play for ease of assembly without making it too wobbly. Like if I'm working with 3/4" stock and use a .75 router bit to cut the grooves, should the boards be .73 thickness? .72? Etc.

Just did a test piece where I got the boards to around .74, but found the fit to be too tight.

 

[Michael Kellough]

I’d make the cuts with a tracksaw on an MFT. Finish with a jig saw and a chisel.

Will this bookcase have a back? I hope so, mounting three uprights on a random wall precisely enough to insert a half dozen shelves would be an extraordinary feat. Although if you can get the top and bottom shelves in you’re pretty much home free.

 

[P_K]

I've done something similar with Baltic Birch plywood and I can say it was a struggle to assemble. If I had to do it again, I'd be inclined to use these: https://www.festool.com/accessory/j...r-joining/domino-connectors/203167---msv-d825