Spoilboard questions and issues

I want to use a Spoilboard on top of my Shapeoko XXL Pro. I did make a spoilboard and it maintained being flat until I surfaced the top of it. The surfacing did not go as planned and some issues occurred.

The next day I went back downstairs to work on the spoilboard again and from about the center to the right hand side it bowed up off the table. Prior to surfacing it, it had not done this, so the surfacing apparently caused it to bow so now it looks like I will have to make a new spoilboard.

What can I seal it with to prevent this from happening again ?

Also is there any easy way to get 240 t-nuts out of MDF ? I need to get them out of this warped spoilboard.

And finally I got my Tramming gauge today, should I be tramming before or after trying to level the spoilboard as my previous spoilboard attempt resulted in very noticeable vertical ridging across the entire spoilboard

And finally how do I secure this spoilboard to my hybrid table ? Do I need to drill holes into the aluminum extrusions or just screw it into the hybrid tables MDF boards ?

Rather than try to remove the hardware, my inclination would be to:

  • spray the underside/sides w/ spar urethane — at least two coats
  • bolt it down, pulling it reasonably flat — my suggestion would be to use the T-tracks for securing things
  • tram it again

FWIW, I tried the array of threaded inserts a couple of times — I vowed that if I ever did it again, I’d set it up so that I could either access the underside and install the hardware from underneath, or use hardware suited to installation from above, and that I would only drill and install holes on an as-needed, where-needed basis — that way I’d be sure that a given hole/insert was used at least once.

Lastly, unless there’s something specific about using the threaded inserts for your work, I’d really suggest giving the Hybrid T-track a try — it’s really amazing, and the spacing almost always can be made to work w/ the various clamps we sell — if it doesn’t fit naturally, it can usually be made to work w/ a couple of cauls and a few pieces of scrap material.

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To extract tee nuts use a punch from the topside. They are reusable. I have made 4 spoilboards and used same tee nuts.

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I didn’t want to mess up the hybrid table so thats why i made a separate spoilboard as I will be doing 3d carving (hopefully) and I had seen a lot of people put spoilboards on top of their Shapeoko’s default table.

I honestly don’t know what I’m doing thats why I’m all over the place here. I just keep reading posts here and watching youtube videos and keep getting deeper into trouble/issues and more questions

I have never owned a CNC machine before, never really did wood working before. My enclosure for my Shapeoko is my first major woodworking project from my own plans, its passable but could have been better. The first version was a disaster.

Do you mean like a nail punch or something else ?

Thread a bolt into it and knock it through.
Or use anything that will fit in the against the top.

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I use a 1/4" flat punch but as Neil suggested thread a bolt in and tap it with a hammer and it will fall right out.

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One thing to note here is that on previous models of Shapeokos folks used to install a supplementary MDF wasteboard on top of the MDF bed because…while the MDF end could have been used as a sacrificial wasteboard, replacing it was not easy nor convenient (you would basically have to disassemble the machine back then). So it made a lot of sense to ADD a wasteboard that could be easily replaced when damaged. A number of videos you see might be from that period of time when it made sense, and might be from folks who kept that old habit.

Now, with the latest generation of Shapeoko and their hybrid table, I would argue that the situation is different: the MDF slats that go on the hybrid table slots are designed to be easily replaceable without impacting the machine’s structural integrity/squaring/tuning, so there is really no need for a supplementary wasteboard on top of them. This is especially true if you learn to be a little careful about your depth settings. I now very often use “stock bottom” as the Z zero reference, which pretty much guarantees that the toolpaths will barely scratch the surface of the slats when doing full depth profile cuts. Anyway, I thought I would mention that in case that can simplify things for you by not having to worry about installing a supplementary wasteboard.

We have literally all been there, it’s part of the CNC addiction :slight_smile:


@Julien, isn’t it kind of a pain in the butt to completely surface all the slats on the hybrid table? Aka, if you want all the slats to be flat from front edge to back edge and left edge to right edge and not just a flattened recess in the cuttable area? The last I saw, the procedure involved having to keep swapping the slats around to get all of the parts flattened. At that point, I wasn’t even convinced you’d end up with something that was truly flat due to slight differences in where and how the slats are finally screwed down.

FWIW, I’ve never tried to flatten the slats (I use SMW fixture plates and a sacrificial wasteboard on top of that if I need it for something specific) but when I first received the machine I was relunctant to do flatten the slats in the hybrid table because of what I thought was the complexity of that process.

I did this once. And I did have to make an adjustment in Z to get the far left & right areas outside of the cut area. Front to back worked well. Although the screws holding the slats are not evenly spaced ???

I’ll be doing it again today/tomorrow, I think I’ll cut a relief around the outside of the cut area 1/8 - 1/4" deep. I use a 3" sanding disc to flatten the spoilboard, taking maybe 0.005" so that should last quite a while.

I thought of just adding a secondary spoilboard on top, but then I lose that much Z space, and also the T-slots.

Well, there is a 30-day warranty — that said, yeah, I just nicked one of mine the other day — in parallel to how I describe my truck:

It’s a spoilboard, I expect it to get scratched up when working

It’s not something I would enjoy doing every week, but honestly it’s still relatively simple

  1. surface the bottom half of the slats (except the two outer ones)
  2. flip them and rerun the surfacing job to do the other half
  3. if you really want to squeeze every last inch of travel/work area, swap the two middle slats with the two outers ones and repeat 1 and 2 on the two center slats only, then swapped them back to their outer slot.

On a XXL I don’t even bother, I just surface them to a smaller thickness and you will only have to do this once (they just won’t support your stock, but the work area loss on an XXL is minimal)

As I mentioned, since I’ve been using the “zeroing on stock bottom” method, I rarely ever cut into the slats anyway, so I have not had to resurface in the last 6 months.

Like Tod mentions there is the matter of losing some Z clearance, and losing the ability to use T-slots. But hey, the beauty of those machines is that everyone can customize their setup at will very easily, so using a supplementary wasteboard is an option for sure. I was trying to convey to @cog that it’s not a mandatory part of the setup now, while it pretty much used to be. I also get that while one is in the process of learning CNC, it’s a good safety net to have to feel at ease.


As an alternative, you can surface down the outer slats and that portion of the inner slats so that they are level w/ the Hybrid T-track, or just a bit higher:

or see what I did on my XL:

Thanks for the explanation. It doesn’t sound too bad but definitely sounded more intimidating when I was brand new to CNCing. I’m still not convinced you end up perfectly flat but since you surface the cutting area in its final position that’s probably not critical that the outer parts are flat. And that’s a good idea to surface the outer slats lower!

Also, I definitely agree with the zero on bottom. More people should do that! In the dozen or so jobs I’ve run on the sacrificial wasteboard using double sided tape, I haven’t even cut all the way through the tape yet let alone into the wasteboard!


Chris, it may not be as convenient as a complete spoilboard, but for the last couple of months I’ve been using a bunch of strips of 1/8" plywood (about 1"x12") arranged loosely under my workpieces (on top of the MDF hybrid table). The clamping pressure provides enough friction that I’ve had no problem with them shifting. As they get torn up, I can just make more. Anyhow, it’s another option.


Is this what I should be getting to spray it with to seal it ? https://www.lowes.com/pd/Minwax-Helmsman-11-5-fl-oz-Oil-based-Varnish/999913673

Pick any moisture-resistant finish you are comfortable applying/using.

I used a spray spar urethane.

Should it be oil based or water based ?
What about polyurethane ?

I have no idea how any of this stuff reacts on MDF

Water based will swell your mdf more than oil based. Oil based will soak in better but if you have any scraps try it out before applying it to your spoilboard. Oil based like polyurethane and the spar urethane are oil based and as the urethane name implies is also a plastic. Thinks like polycrylic is waterbased and will penetrate but tends to swell and raise grain. Now MDF does not have grain but it will swell more than the oil based.

I do not put anything on my spoilboard but I am not machining metal with any lubricants. So mileage varies depending on what you will be machining. I live in East Texas where the humidity is 80% most days. So it is hot and humid. Unless you live by the sea humidity may or may not effect your spoilboard because mdf is a mix of sawdust and glue. There are different types of mdf and some have more sawdust and some have more glue. There is no specifications for what you get.

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I have a question for the group. If I seal my MDF waste board, will I be causing issues?

Mounting holes “Screw”, when I attach the board, won’t I be scaring the protected surface allowing moisture an access point? When I cut into the MDF, should I follow that up with a spray of sealer?

Some of our climates are not helpful to the MDF. That is why I call it a waste board. I use it up, waste it, then replace when used up.

Will sealing it make it last longer? Will the extra steps used to re-protect it save us time in the long run?

Not trying to be obnoxious. Like anyone if I can save a dollar, I will try.