I’ll go through and annotate some of them now. The design on this was like 10x the work of actually building it. I’ll attach my cutlist too. I used ultralight MDF for everything but the front and back strip since it wasn’t available in 10 feet but I think I would probably just end glue 8 foot ultralight if I did it again. Ultralight MDF is awesome stuff.
The strip with the threaded inserts is just for clamping. It’s 3/4" baltic birch. I’m not too confident this is what I want for a permanent solution so I just glued them on temporarily with contact cement. So far it seems good… I used my dewalt pen holder design to have the carriage draw a box around the cuttable area of the table and glued the strips along x=0 and then placed the top piece to accommodate an 8 foot sheet. The spoil board is only 1/2" foam so it makes a natural registration lip for what I’m cutting. I also have softwood blocks glued to the webbing strategically under the top skin so I can have some very strong threaded inserts directly in the table too. I’m wishing I had gone metric… finding 3/8" nylon threaded thumbscrews is a lot harder than getting metric ones.
Attaching to the wall… here is the disclaimer. I’m not an engineer and don’t follow my example thinking I know what I’m doing… I don’t. Hanging hundreds of pounds on a wall can be dangerous if done improperly and you should run your design by an actual engineer to make sure it’s safe. I chose to attach two three feet sections of 2x6 to the wall using six long structural screws in each side… two per stud, each into three studs. I just found out about structural screws and I’m never using lag bolts again. Then I bought some box steel and drilled it out and attached that to the 2x6’s with more structural screws (six per side). Everything is bolted together with grade 5 bolts 3/8" diameter. I doubled up on the 3/4" MDF where the bolt goes into the table and used a T-nut inside the table. There is also a 2x4 ‘cradle’ held together with framing angles and structural screws that goes under the bottom and up both sides that the bolt goes through. The idea being I can add a shim between the 2x4 and table to compensate for sag or worst case add a hinged adjustable height support leg. The swing arms should be as long as possible… mine would have been high up the wall near the ceiling but I just didn’t have the energy to move that huge heavy air cleaner mounted to the ceiling. The secret sauce is attaching rigid casters to the back and mounting a track on the wall for them to run on.
Not sure how the gantry could fall off… on a 4" table there is almost no wiggle room. The bottom pipe clamps have about 1/8" of clearance. There is only 1/4" gap on the sides and the carriage just slides to one side as you lower the table. I have a 1/4" spacer I can slide between the pipes and the table on the top side but I usually forget to with no ill effect. The one thing I do is raise up the carriage all the way and clip on some clamps to the pipes to keep it there so the lead screw and pipes clear the back wall. I posted this clamp on thingiverse.
4-inch-ultralight-box-without-rails.pdf (356 KB)