What to hold the bleeder board down with?

[jeffreymcgrew]

So we're going to soon be taking the plunge and going for the vac table. We're going to base our design off of David Buchsbaum's, with the T-rails and eight zones, as we do a lot of different types of cutting and I think this setup will work best.

However, one thing I'm confused about with that setup with the T-rails is: when you put the bleeder board down, you obviously don't want to glue it down. But if you don't glue it down do you get a good seal at all?

For those with removable bleeders: what do you do to hold the bleeder to the table?

[Brady Watson]

1) Countersunken screws
2) Brad nails
3) Tape around perimeter
4) Nothing. Let Vacuum hold it down.

-B

[jeffreymcgrew]

I'll take number three for the win. ;-)

Thanks again Brady

[harryball]

I used 1 and 3 before gluing. You need to realize the bleeder board can buck up with the vac off. I got in the habit of always running the vac even if I was doing a screwed down project.

Robert

[Brady Watson]

I tape my BradyVac jigs around the perimeter. There is enough stick to keep it from moving when repeatedly slinging. slapping and otherwise throwing plywood on the table during production runs...Foil tape is the best...blue painters tape works too.

-B

[pfulghum]

#4 for me - Nothing let the vacuum hold it down.

I don't run tape nor seal the edge of the bleeder. I have a vacuum gauge on the system, I see very little difference when I used to do those things.

But then again your mileage may vary.


-- pat

[beacon14]

#4 mostly but after a while sawdust can work it's way under the bleeder and cause unevenness - not really a problem when always through cutting but I'll clean under the bleeder when a level table is important. Taping the edges can help (with both the sawdust and the vacuum) until the tape wears out.

I'll use brad nails if I expect it to be in place for a while.

[knight_toolworks]

I ran a channel on the undersheet for a bead of glue. because I do most of my cutting without the vacuum going. but I have a choice I can have really flat with the vac on or without it but I don't get both. most of the time I need really flat without the vacuum so I surface the table without it on. but it would be nice to always have it flat.

[sawkerf]

I installed T-nuts underneath the plenum so I can screw it down using nylon bolts. I just run a file to drill and countersink the bolts when I change the spoil board. It holds tight and no buckling and no sawdust in the plenum. Kip

[jeffreymcgrew]

Kip: now that I've thought about it some, I think that's what I'm going to do. We're planning on putting t-rails into the tabletop anyway.

[sawkerf]

What can I say ? Great minds... Oh, you can get the 1/4 - 20 plastic bolts from lowes or ou can get them from Grainger. I bought 500 from Grainger a while back for about 35 bucks. Those should last a while. Good luck, Kip

[joelschuman]

Try these bad boys instead: McMaster item# 91345A684 Fiberglass Cap Screw Flange Head, 1/4"-20 Thrd, 3/4"l, Fully Threaded. Stronger than nylon, especially after you plane 'em down to 1/8". Use thin nylon washers under them. 90295A140 Nylon 6/6 Flat Washer 1/4" Screw Size,.252" Id,.472" Od, .054"-.070" Thk.
And instead of tee-nuts, which require drilling thru the plenum and have to be installed before gluing it down, use threaded inserts. If the plenum is MDF, inserts tear it up, so I oversize the holes and set 'em in epoxy. 92105A100 Zinc-alloy Knife-thread Insert For Wood Hex Drive,w/flange, 1/4"-20 Internal Thrd, 33/64"l

[davidp]

Steve,

Once our spoilboard/bleeder board got down to around 6 mm we resurfaced it then placed another 18mm sheet or whatever was on hand on top, then took about 1 mm of the surface, flipped the new board and then glued it about 12mm in from the edge all the way around to the old board. When the new board got down to around .5 mm we repeated the process and now after approx 10 layers our spoil board stays flat and level with or without the vacuum and does not move.

regards,
David

[brian_h]

I decided to create a removeable t-slot table that goes on top of the bleeder board. My bleeder board will be glued down.

[knight_toolworks]

that would be nice. I keep goofing mine up when a long bit slips. cuts so deep I have to replace the whole sheet.