Hindsight being 20/20, I now realize I should’ve got a 60120 as it would’ve given me more options for holding a full 4x8’ sheet of plywood! What are some options people have come up with that doesn’t involve a vacuum table, screws, or composite nails? Any thoughts shared would be greatly appreciated.
I think you still have just enough room around a standard 4x8 sheet to fit in some small edge clamps (assuming your spoilboard is bigger than 4x8, the 4896 working area is actually 49.5 x 98.75, plus room around that). Fix some hardwood strips along two edges to press against, and use a wedge-style clamp along the other two edges. I don’t think a standard wedge will work, but something like
https://www.printables.com/model/393687-cnc-wedge-clamp
might. I use something like this to hold down hardwood when I need to surface the whole top.
Of course, this assumes your machining doesn’t pull “up” too much in the middle. I would tell the cnc to drill screw holes in places it knows will be out of the way, and screw it down there. Or you could use double sided tape to hold it down. The overkill solution is to put a grid of threaded inserts in your table and have the cnc drill access holes to those into the plywood, so at least you’re not destroying your table with wood screw reuse.
You may find you have room to fit a few standard down-force edge clamps in your design too.
Alternately, if your spoilboard is also exactly 4x8’ you may find there’s an inch or so of gap around it? A small clamp might fit there too.
Another option would be to remove the rubber rail guards and replace them with hardwood guards that extend up enough to push plywood against, perhaps even with integrated clamping solutions.
Remember, think outside the box 
The other option, of course, is to call Avid and get a quote for an upgrade…
As far as really outside the box, if you have plenty of Z space, burn some. Lay down 1 or 2 4x8 sheets. Screw them to the spoil board. Lay down 1 or 2 52+x100+ sheets, counter sink screw them to the previous pieces. Now you have a 2+ inch lip around a 4x8 sheet that you can work with. Choose your clamps, and have at it.
Thanks for the replies! Both are great options as they are relatively easy to implement and easily removed if they get in the way of other jobs!
This is along the lines of what I was thinking.
3D Print these and attach along the rail with the Linear Rail Dust Covers
I am moving my shop in a year or so and will look at that option then.
This also a great idea! I may consider this when I replace my spoil board down the road.
I know you said no screws, but just for some feedback; I’ve run hundreds of sheets on my Avid and always use one screw about 1/2" in from each corner. The spoilboard still holds fine and I just need to remember not to nest any vectors in the extreme corners of the sheet. If the spoilboard ever gets to a point where it can’t hold the screw, simply mill out a rectangle and glue in another section of MDF.
I know you said no screws. But it just works and it doesn’t require buying or modding anything.
I find the composite nails a perfect solution here, despite OP calling for alternatives. Unless the plywood being cut is going to be unfinished and the area visible in the end product. The composite nail will hold firm, will break off clean in the spoilboard, can be sanded/painted, wont damage an end mill, etc. If you’re doing repeat work and want to spend a little time with setup, you could engrave crosshairs or something in a spoil area of your ply to indicate where you can nail/screw it that won’t interfere with the cutter or show in a final product. Just some thoughts for the next person browsing the topic.
I’m planning to what @corbin did in this video, but I’ll be using 2 foot long sections of t-track and mounting them so they overhang the linear rail covers (and just short of the risers as they move!). The should be enough room for some toe clamps (also designed by Corbin!).
Yeah! I just use the toe clamps; the spoilboard is 49" wide (MDF standard), and a 4’ wide sheet has enough on the edges to clamp it down just a bit. Having it hang over the rail covers an inch would be super helpful to have a little more clamping area – it might be hard to completely machine that spoilboard area flat with the CNC though, so make sure a 2" bit can make it.
Thanks Jay,
I am subscribed to your channel and have been watching you for years (even before you got your first Avid)! I am glad to see you recently purchased another and hope you will be creating new content as to how you are using/accessorizing it.
I did purchase your Spoilboard files and designed a hybrid version based off of your dog holes and the MicroJig System. Having used two sheets of MDF glued to each other I figured I could resurface until the MicroJig slots start to cut into the first layer and replace the second layer at that time. I also squared the top layer MDF around the perimeter and now have 48.25" width.
The pre-finished plywood I get from my local supplier is 48.5"x96.5" so putting screws in the corners would probably work still.
I am now considering your suggestion and may glue MDF or hardwood blocks into the corners to regain 49" for screws as you mention.
Thanks Corbin,
Yes, this is one of the options I am considering! See my reply to Jay above. Toe clamps may be a little tricky but I am sure I can model and 3D print an option that will work.
Also have watched your channel and have learned from it. I am still figuring out what works best for my workflow and projects that I may have coming up.
Yeah I like this idea! It is close to what I have in mind. I have already created and installed a 3D print that is a bump/stop for the plywood. I will add some other 3D printed plates that I can attach toe clamps to. I am only adding the bump/stop on one side to allow easier loading of sheets. I cut and re-installed the rail guard dust covers for now. I do not cut full size sheet goods all the time so I think this system will get out of the way when I don’t need it.
Cool!
I have two minor comments on this printed bump-stop…
- It looks like you already do this, but for anyone copying it, print it on it’s end so the layers run from the bump down to the screws.
- When I do stuff like this, I include a bit that extends into the slot the screws use (see photo). This would brace the bump against being moved by the plywood, making it more predictable position-wise. You want this brace to take the force, not the screws.
I might also put a triangular brace between the two faces but it’s unlikely to be actually needed. You could position it at one end so it’s against the print bed, for simplicity.
Bonus points for printing it in Avid Red though
Yes, printed on end. Seems pretty secure but if I notice it moving I will add your suggestions.
If anyone is interested in the files for these prints as it progresses let me know!