Spoilboard size?

What preferable size should the spoilboard be at if my cutting area is X 800 and Y 1200?
I have found material at exactly 1200x800mm but not sure if that is enough…

Ideally you’d want it a bit larger to support and hold down your work piece on the opposite side of the cut if needed. But I don’t think it would be a huge deal if you didn’t. You should be fine. You just may get a bit of chatter if you mill to the extremes of you cutting area.

It should not be bigger than your max workspace plus half the diameter of your surfacing bit of your ever want to plane it. :slightly_smiling_face:

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This is the correct answer.

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Assuming that you are using a CNC machine and that the spoilboard will be used to hold down the material being cut, a good rule of thumb is to have a spoilboard that is at least as large as your cutting area in both X and Y directions.

In your case, if your cutting area is X 800 and Y 1200, a spoilboard that is exactly 1200x800mm would be the minimum size you should consider. However, it’s generally a good idea to have a larger spoilboard if possible, to give yourself more flexibility in your workholding.

Having a larger spoilboard also allows you to re-surface it multiple times before needing to replace it, which can save you time and money in the long run.

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Having oversize can be a negative because after surfacing, you will have a shallow pocket in your spoilboard with a lip around the outside, which is a problem when loading larger workpieces that hang outside the working area.

If you will never load larger workpieces, then you could go larger and you could mount workpiece fences along the X=0 and Y=0 if you wanted. Or those could be mounted to the machine and not mounted to the spoilboard. It’s whatever fits your style of work holding.

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smart thinking

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You could, if you did want to go with a larger with the board, mill flat as much as the machine would allow and then flush up the edges with a bent neck chisel.

It’s archaic, I know, but stone age tools do come in handy every once and a while! :laughing:

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