Holding or hold downs for Cutting

[Bill George]

Thinking now for cutting 4x4 sheet stock plywood and other. What besides a vacuum table are people using, in the past I have just screwed down to a spoil board and cut leaving tabs.

[Gary Campbell]

Bill...
If you are going to cut sheetgoods commercially, vacuum is the only viable option as no other method sucks the sheet down to the spoilboard. Even with good vacuum, some sheets are so warped that they wont lie flat. Once you go vac, you'll never go back

[Brad Shipton]

Clamps, screws or the carbon fiber nails is about it. The carbon fiber nails (Raptor) work so so, but the cost of the gun is about 1/2 the cost of a homebuilt vacuum. A vacuum is sooooooooo awesome for sheet goods. The Hurricane is a good option, but there are many examples of home built ones online.

[Jim Becker]

There are many methods that work well. I agree with Gary that someone frequently cutting sheet goods will be best served by a vacuum table and the initial cost will payout with both ease of use and speedier material changes.

For a 4x4, Black Box recently released their new Cyclone, a mid-sized unit that's sized well for 4x4 machines and at a lower price point than the larger Hurricane unit. The advantage with Black Box is that their units work on single phase power.

I don't do a lot of sheet stock (today will be one of the rare times as I'm cutting some things out of Advantech for Professor Dr SWMBO's beekeeping operations), so I haven't missed not having a vacuum table, but I am using vacuum for fixtures with a small unit I already had in the shop. Otherwise, I use a combination of clamps in tee tracks and screws, depending on what I'm doing.

[Mark Bolton]

I would argue in this instance that vacuum shouldnt be arbitrarily relegated to sheet goods. We process a lot of solid wood (hard maple) glue ups. School furniture. Our process is to glue up blanks rough (rough sawn). We will toss as many blanks as we can on the CNC allowing for scraps on four sides to cage them in. We will toss on scraps of shiny laminate scraps, melamine, whatever that will pull down with the vac. We will then zero off the corner of the blanks and set an XY an inch - in X and Y, and setup a deck off pocket tool path 2" larger than the blanks we've tossed on. Use a rubber mallet to peck the shinny wood scraps tight to the rough sawn blanks with the vac on, til everything is pretty tight. Then we will fly gut the face with conservative passes (we use a 3.5" fly cutter and will run .01" passes til we are down to .080 or .100). Smooth face, we flip, and rip.

We often use the CNC as a planer or widebelt sander. If you think about it, even if its a little slower, you are jointing your rough sawn glue ups or blanks, and you are surfacing them flat with NO chip slamming in the planer, your not standing there feeding and tailing the planer, your eliminating your jointer step, in addition youve likely free'd up the floor space for a jonter AND a planer. And, to beat the band, you have multiple parts sitting on the machine being jointed and surfaced one side, and then flipped and the other side, and all the while.... YOU ARE DOING OTHER WORK. So imagine taking a board, rip, joint, go to bench, glue up, out of clamps, across the jointer to flatten, then through the planer to thickness,.. that is all eliminated. We straightline on the slider, glue up, on to the CNC, and then we are doing other work while the CNC flattens, we flip, run the other side and done.

We shoot all waterborne. So the CNC is a win win there in that the planer will inevitably develop a knick in the knives. We can either open up and shift the knives to stagger the knick or swap them out (all the while no work is being done). If we leave the knick, the planer pounds down the wood fibers where the dull knick is, we then sand out the ridge the knick left til the board looks perfect. Then it goes into finish and the water bourne finish swells the compressed woodfibers back up at the knick and your perfectly sanded and preped part has a light colored raised line running down its length where the knick in the knife was.

With the CNC there is none of that. Fast pass your deck-off and run a slow second pass and your parts will be nearly 150 grit off the CNC. You save on abrasives. You save on grueling sanding times, you save all the way around.

Even in a solid wood shop, if you could capitalize on the CNC Id venture its like adding 3 men to the shop.

[Jim Becker]

Mark, you make a good point about vacuum being more useful than just for sheet goods. But for those of us with smaller machines and smaller budgets, we have to consider the cost/benefit given that a really good vacuum table setup costs a larger percentage of our CNC router investment. I'd certainly consider adding it if I feel it will increase my revenue stream or better support what I do, but at the present time, I just can't justify it.

And thanks for the reminder of all the other things we can do beside "cutting things out". I fully intend to use mine for surfacing slabs and other solid stock work, you can be sure.

[Mark Bolton]

Mark, you make a good point about vacuum being more useful than just for sheet goods. But for those of us with smaller machines and smaller budgets, we have to consider the cost/benefit given that a really good vacuum table setup costs a larger percentage of our CNC router investment. I'd certainly consider adding it if I feel it will increase my revenue stream or better support what I do, but at the present time, I just can't justify it.

And thanks for the reminder of all the other things we can do beside "cutting things out". I fully intend to use mine for surfacing slabs and other solid stock work, you can be sure.

Where it really shines for us is flattening, and surfacing material that basically sands like iron (Hard Maple is a perfect example). You take a good sized hard Maple glue up or even any part, and run it through the planer, then through the sander, and you've still got linear sanding scratches that are a nightmare to sand out with an orbital. Now of course if you had a massive 5 head orbital production sander, but in a reasonable shop. We (mainly I) am pushing myself every day to run operations I never would have thought to run on the CNC. The surfacing for us is a real game changer. Like I say, a couple quick hogging passes, and a final slow pass and your knocking down hard maple with 150 grit on the RO and done. Its night and day.

Its interesting (and very nice) how little our planer and sander runs now. Old routines are hard to break.