Been thinking about my LR3 build (order has shipped!!!) and was wondering if anyone has done a ‘cutting table’ style top? Picture a torsion box but without the top or bottom - it’d just be an open grid of squares.
I have 2 reasons for wanting to try this - 1) good plywood is freaking expensive right now, and if I’m gonna build a torsion box, I could save $$ by leaving the top and bottom off if it wouldn’t really be needed, and 2) I have an idea for setting one or more squares up with vacuum pulled from below for awkward work holding.
So the entire way a torsion box works is by having the top and bottom planes separated rigidly… And without either of those two, you dont have a torsion box. Its those 2 top and bottom sheets that give it the real strength, not the ribs
Any sheet material will do to create the torsion box - use cheap mdf and make it 4mm thick if you must. In that case you’d rely on your spoil board for the integrity of the top, but you’re doing that anyway. You can chop out between a few of the grids without messing up the torsional rigidity too much and can even build in a hinged panel to do the sort of thing you are talking about.
The cutting table style would be a bit difficult to keep straight in timber too - I imagine you’d have to make the webs out of ply or mdf to keep it stable, although without the thickness limitation that the LR@ had that’s more than possible.
My “torsion” table is entirely constructed of MDF - because cheap.
Yeah, I understand how torsion boxes work - I’ve built more than one - but a well glued up grid made of 3/4” material is still dang stable.
I guess the question is how sturdy does it really need to be? The material that’s being cut won’t cause it to flex at all, does the milling produce a lot of downward force in a small area?
That was my original plan - 3/4 MDF - but it’s not great with holding vacuum, so 3/4 ply was plan B.
If I give up on the vacuum idea, I suppose I can go back to MDF and throw a 1/2” top and base on it for not a ton more $$ than just making the grid out of good 3/4 ply.
My table is just a sheet of 1/2" particle board on some 2x3’s. I can say it works but is not enough. If I lean on it too much I can affect the touch plate readings. I think a skin on the bottom would help but I want to make a nice table for the first time. So I hope to use this to cut another.
I’ll do a test in mine. My table is 1750mmx3450mm or something silly like that, and I think I can lift one corner by 1mm and it’ll pull another leg up with it …
I’m not sure what you plan on using to generate the vacuum. I’ve seen vacuum tables constructed out of MDF. The sides and bottom were painted with a couple of coats of latex paint to seal the MDF. The top was surfaced/skimmed to “open the pores,” but no holes were drilled. The vacuum is pulled through the MDF. Also, you might get away with thin, cheap material for the bottom…underlayment, hardboard, or white hardboard.
I think that’s the ticket here - I’ll use MDF and if/when I get the vacuum bug going, I’ll spray a couple coats of a cheap thick paint (like PVA primer) on it.
Soooo yeah - boring old torsion box with 1/2” MDF top and bottom.
Now to get to work!! My shipment arrives today!! B
Hey! This is super awesome and I’m very interested. Will be driving out to Maryland May 14th. Would love to swing through and pick up if you can hold onto it until then? Can you send over any measurements so I can verify that it’ll fit in my LR4?
