From contributor M:
We use 1-1/4" MDF in 5 x 10 sheets. I have found that the thicker the spoilboard, the better the parts are held on the table. We found a unit of this material at Blue Links (formerly Georgia Pacific).
From contributor J:
Why do you think a thicker spoilboard holds the material better? I understand that within the exposed spoilboard (cutter kerf), the vacuum loss will be less, as there is more resistance from the thicker spoilboard, but exactly how does thickness equate with more vacuum? Doesn't thicker mean longer time to develop full vacuum? If you're working with 2 spoilboards, as is anyone who is doing production work, isn't 1 1/8" and its extra weight causing operator fatigue?
Our vacuum gauge consistently reads better as the thickness of the spoilboard decreases. With 500cfm, we lose no significant vacuum through the kerf, therefore from where I stand, thinner is better as long as you have the vacuum capacity.
From contributor M:
I know that it seems backwards, and I don't know technically why, but thicker equates to better hold down of parts, particularly small plywood parts. I do not know what type of machine you are using, but this is true, at least, for the Biesse Rover 30. We find on a consistent basis that as the spoilboard gets thinner, smaller parts begin to come loose. Now you have to onion skin (more time), or change the spoilboard. It also helps if you edgeband your spoilboard. As far as operator fatigue... get someone to help you! You get the added benefit of having to change your spoilboard less often.
From contributor L:
We use 3/4" MDF, surface both sides with a 4" fly cutter before use, sometimes edgeband with PVC, and use 40hp vacuum and 5x10 table, which works fine.
From the original questioner:
What HP vacuum pump is everyone using? I have a 25HP Quincy.
From contributor K:
That's a pretty popular pump. Keep the filters clean and the oil changed! Either vacuum the filters out or use compressed air and blow from the inside out.
From contributor C:
Contributors M and J are both correct, and I suspect it has a lot to do with the type of pump. If you are trying to hold small parts well, you must have the CFM at the pump to replace the air being lost. Biesse machines usually use high pressure pumps which have a lower CFM rating and can not make up the air being lost as you open up more table during cutting. These pumps work very well at holding solid parts and fixtured parts. It could be said that the 1-1/4" material works better for you with this style pump because it allows less air to flow due to thickness. Pumps that produce high CFMs (450cfm and above) usually work better with thin (1/2" to 3/4") spoilboards. Contributor M is doing the right thing by sealing the edges of his spoilboard with edgeband. Paint works well, too. 38-45lb MDF is what most of the industry recommends. I would suggest looking up info on your vacuum pump to see what the CFM rating is at what hg. The higher the CFM at a given hg, the better for small parts.
From contributor D:
We use a 3/4" MDF spoilboard and a 1/4" MDF wasteboard. I sealed the spoilboard edges and a 2" strip around the bottom edge where it sits on the gasket with epoxy. With the 1/4" wasteboard, I never have to touch the spoilboard. It's light enough to move off the table loaded with parts. Easy to flip over when I need a fresh surface. Some nests reach 40-50 parts, some parts smaller than the labels we use (1x3). We have an 18hp Becker pump and rarely have parts move. After using both sides of several wasteboards, I flycut them all, both sides, to the same thickness again. I can usually do this twice before they're too thin to lift without breaking. It seems to me that the combination of the 3/4" and 1/4" MDF gives me better holding power. Go figure.
From contributor G:
If your primary material size is 4 x 8, then that's the size spoilboard you should be using.
From contributor J:
We have a phenolic table which does not require a gasket, and I use a 3/4" MDF spoilboard which I try to cut into only 1/10mm. The first thing I do when preparing my spoilboard is to edge band with 3mm PVC and dress 0.5mm off each face to expose the less dense core of the board. I don't know why anyone would use a "wasteboard" on top of a spoilboard. We have reverse air on our table and rotate two spoilboards continuously, so our spoilboard is our wasteboard. When we set up properly, we can run a spoilboard for weeks. We start at 18mm and cut 0.2mm each time we dress the sheet. Our pump is a Bekker 25hp with pulls -7.2 inches mercury at slightly over 500cfm, and our table size is 5x12, but we generally run 4x8 material. One of the last posts said it the best - if you have a pump with high CFMs, you are rewarded with proper hold down vacuum, and you can work with multiple spoilboards and save time leaving out the onionskin step.
From contributor R:
We use 2" thick LDF for spoil boards on our 5' x 12' machines. The Airboard comes to us in 5' x 10'. Our 40 hp vacuum pumps have no trouble sucking through the board and holds better than using 3/4" MDF. The 2" thickness allows us to go a month before changing spoil boards, so as you can imagine, these last much longer. Sierra Pine makes this.
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