First Spoilboard Setup for a PRO4896

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I’m commissioning a used PRO4896 and trying to settle on my first spoilboard setup. I’ve read everything I can find here on the forum and watched Corbin Dunn’s and Jay Bates’ videos. There’s a lot of good advice, but I’m trying to keep my first setup simple until I learn what I actually need.

My primary interest for the machine is curved and more complex furniture work, although my business seems to attract plenty of cabinet builds as well. I’d like to use the Avid for cutting cabinet boxes and, where practical, machining Domino mortises or Lamello grooves as part of the CNC workflow.

Right now I’m leaning toward two full 48” × 96” sheets of 5/8” Baltic birch as the permanent base, with a replaceable 49” × 97” MDF/MEDEX spoilboard on top.

For workholding, I’m considering a 20 mm/96 mm dog-hole grid and/or MATCHFIT grooves, along with composite nails where appropriate. I’d prefer to avoid T-track initially because it seems to add expense and unnecessary complexity. I may add a removable vacuum fixture later.

Avid specifies the PRO4896 cutting area at 49.5” × 98.75”. Is it worth complicating the base to chase that last 1.5” × 2.75” of cutting envelope, or would you just build around standard 48” × 96” Baltic birch and a 49” × 97” spoilboard?

For those who have been using their Avid for a while, does this sound like a sensible first setup, or am I overlooking something important?

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I’m still on my “starter table” - two MDF sheets glued together, nothing else. I still just screw into it to hold down the part (or screw down 3d-printed clamps). IIRC I clamped the first sheet in place temporarily, used the CNC to mill all the bolt holes and countersinks, and bolted it down. For the second sheet I clamped it down temporarily, used the CNC to mill a grid of 1/8" holes in it, removed it, spread glue, replaced it, and screwed through all the holes. After the glue dried, I removed the screws and used the CNC to flatten it.

The slightly extra “cutting envelope” range is - IMHO - there to let you get your bit to the outside of a nominal-sized sheet. The extra 0.75" around the edge lets you get a 0.5" bit next to the full-sized sheet (and some sheets are slightly oversized anyway) with some clearance.

If your Y has more “extra” consider adding a vertical table at the end - the extra would let you work around the edge of nominal sheet stock.

And yes, I keep a sanding block handy to remove the “divots” :slight_smile:

Tip for table assembly - the Avid instructions have you cut a length of scrap wood 14 3/16 long and use it to space the many cross-pieces. It’s better to realize they’re on 400mm centers, and use a metric tape measure to lay them all out from one reference end. That way, when you’re CAD’ing up your table, everything lines up better, and you won’t have accumulated error (ask my how I know about that :wink:

(alternately, use 15 3/4 centers, but the key is to measure from ONE REFERENCE POINT)

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Jim Neeb here has a nice spoilboard setup. I downloaded his file and adjusted it a little to suit my needs (extended it from 4’ to 6’). I’m still using it as I haven’t found a specific reason to change. I have the embedded rotary at the front and his file has a separate panel that interlocks with the main panel so it can be installed when not using the rotary, or removed when rotary operations are being performed.

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I think you have a good start there! I would add the t-track as well it gives you more options for work holding. It’s a buy once cry once..

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I would not recommend plywood. MDF is harder, is flatter, and stays flatter. You will want to do a flatening pass on it when its installed, and with plywood you can end up cutting through the different layers which will look like crap and also put the stress out of balance causing more warping. MDF also comes 1" oversized, just like AVID’s machines, so you end up with a sheet that fits the machine perfectly. Also, you can buy MDF thicker than 3/4" - mine is 1" thick. However, on my next one I will probably just glue tow 3/4" sheets together.

Soak a couple heavy coats of lindseed oil into the top of the MDF and that will make it a little more durable and let you set a beer on it w/o the can sweat swelling up a ring on it :slight_smile:

What I use on mine for hold down is a 3" spacing of 3/4" holes. This gives me lots of options for side stops, side clamps, hold down clamps, and vacudogs…and its relatively cheap because you already have a CNC to cut it with. If you do this, make sure you chamfer the top edge to recuce chipout from the dogs being pulled out.

If you are interested, I have my Vectric design here. This includes a front removable section that fits around my rotary, as well as a vertical section below that for doing endwork such as dovetails and tennons.

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Thanks everyone for the additional input. This has been very helpful, and I appreciate the examples of what has worked long-term on your machines.

I also found Avid’s full-size spoilboard instructions and “Spoilboard Project,” which answered a lot of my questions. I’ve decided to skip the plywood and go with two layers of 3/4” MEDEX. The first will mount directly to the rails using Avid’s mounting pattern, and the second will be screwed to the first with deeply recessed screws so it remains removable and replaceable. The additional cost of MEDEX over standard MDF is small enough that it makes sense to me.

I’m still leaning toward starting without T-track and seeing what I actually need as I use the machine. The examples of dog-hole workholding, removable sections, and especially the vertical workholding capability have given me some good ideas for where I may take it later.

Thanks again everyone—I think I have a solid plan for getting my first spoilboard up and running.

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I wanted to add something when I made my spoil board back in 2022 my mind was set that I didn’t want to make a new spoiled board later. I knew I wanted dog holes, t-track, and thick enough to flatten out. I used 3/4 in Baltic Birch for the base and two layers of 3/4 in MDF. The BB ply was good foundation for screwing in the t-track I bought the cheapest stuff I can find on Amazon. And they held up just fine. I did buy longer screws than the ones that came with the t track. I guess I lucked out and live in a near perfect environment near Cleveland Ohio LOL because the table never turned into a giant potato chip. As long as you use calipers to measure your workpiece and enter that into your software you’ll never see those big huge diggins and the new CNC 12 software helps even more..

Enjoy your build!!

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Thank you for the response. I really appreciate your perspective, particularly hearing how your spoilboard has held up since 2022.

Simple, with flexibility to grow, is really my objective as I get started with CNC. Like many people getting into this, I have extensive experience with 3D printing and the Shaper Origin. I feel like moving to a full-size CNC will significantly improve my work, but I haven’t quite figured out exactly how it will fit into my workflow yet. Because of that, I’m hesitant to invest a lot of time and money into an elaborate spoilboard system in the early stages.

Several users have mentioned that they ultimately do most of their work in a relatively small portion of the table, particularly the area closest to home. Jay Bates’ recent video reinforced that point for me. So, after taking in all the great advice here, I think I’ve landed on a fairly simple starting point.

Initially, I’m going to use a single row of dog holes along both the X and Y axes for locating and squaring workpieces, similar to Jay Bates’ recent build. I’ll also add several MicroJig-style MATCHFIT dovetail grooves, probably 8–10” long and evenly spaced across roughly the first quarter of the cutting area. That idea comes from the setup Frank Howarth showed in his CNC upgrade video.

For the spoilboard itself, I’m planning on two layers of 3/4” MEDEX. MEDEX is stiffer than conventional MDF and has better screw-holding ability, which I’m hoping will also make the dovetail grooves a little more resistant to pullout. The additional cost of MEDEX is roughly 50% over traditional MDF, so for the amount of material involved, it really isn’t a huge additional cost commitment.

I think that gives me enough workholding capability to get started without committing the entire table to a system before I really understand how I’m going to use the AVID. As my workflow develops, I can always add more dog holes, dovetail grooves, T-track, vacuum fixtures, or something else entirely.

I also just received my new EX Controller upgrade kit today. From what I’ve been reading here about CNC12, the surface-mapping/compensation capability seems like another useful tool for dealing with small variations in bed flatness.

For now, I think this gives me a simple, flexible platform that I can grow into rather than trying to anticipate every possible use before I’ve even started cutting.

Thanks again to everyone who offered advice. It has definitely helped me work through the options and settle on a starting point.

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Is the surface mapping part of the Avid CNC12 package?

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I reread my own post… Not in the sense you’re thinking of (and my post suggested).

I checked the current Avid CNC12/EX documentation. The standard Avid CNC12 package includes “Calibrate Work Surface Location,” but that establishes a single Z reference for the spoilboard relative to the tool-height setter. It does not map a grid of Z heights across the entire 4×8 surface and dynamically compensate the toolpath for variations.

Sorry for the confusion.

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CNC 12 does have a digitizing feature that can use a KP1 or KP3 probe to digitize a surface. It’s not “dynamic” in the sense that it will automatically adjust Z during a cutting operation, but you can import the resulting point cloud into a design software and convert to a surface. I’ve installed the KP1 probe about a year ago and did some very limited testing just to ensure it worked to measure some items and it works well. If I recall correctly the Pro version of CNC 12 has a limited number of points that can be probed, about 5k I think. The Unlimited version of CNC 12 has vastly more if not unlimited.

I saw a YouTube video where someone used the probe in CNC 12 to digitize a surface of wooden handle to map it for a subsequent checkering operation with a v-bit. I don’t know if it was an Avid machine, but the controller can do it. I’ll look for the video and post a link if I find it.

Pertech 12
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Well damn, appreciate both of you. This is pretty rad - I need to be retired so I have more time to mess around with this stuff.