Spoil Board

[Josh_BCF]

Morning guys,

I need some advice on making a spoil board, When I first got the CNC Router (4ft x 4ft) in work I was using 3 clamps (tee bolts) to hold both the spoil board and the board I was cutting out of (Both made of MDF) - The problem I kept running into was that the clamps would slip off during the cutting and either ruin all the signs due to the board moving all over or just the last 2 when it slipped off.

Due to the spoil board being MDF - This is not the best wood to use for a spoil board? I'd love to attach it to the bed but I'm having problems when trying to counter sink the holes (The wood is too soft and will just split away)

I got some little Tee slot bolts and washers - which worked until I tried to put my cutting board on top and screwed it in - at this point the tee bolts came lose and I had to wrestle with it all to get it off the bed.

so I guess whats I'm asking is;

Is MDF suitable for a spoil board?
Whats the best way to attach a spoil board?
Is it best to try and cut the spoil board with the actual CNC? - As my bed is only 4ft x 4ft - I need to use all the wood for the length of the signs I'm cutting - also my cnc spindle has a dead zone on the left hand side of 20cm...

Sorry if this is a ramble but I'm really new to this kinda of thing.

TIA

Josh

[magicniner]

If you use a proper countersink cutter MDF will countersink fine, countersink deep enough to ensure your spoil board levelling cut will not hit the fasteners, if your countersink bottom is anywhere near the bottom of your board it's not thick enough, buy thicker material.
Your spoil board should bolt down to structural points which support the back of the MDF, pulling through should not be an issue.

[Neale]

Josh - you say you are fairly new to this, so I wonder if you are using your clamps properly? I use MDF as spoil board material all the time, and never have slipping problems. Most of the time I don't even clamp it directly to the bed, just keep it in place via the workpiece clamps. The only time I fix it to the bed is if I need to screw the workpiece directly to the spoil board.

Couple of things to watch.

I use a kind of bridging clamp, which is a flash way of saying some odd scrap of hardwood with a hole in the middle. I have T slots along the bed, so the clamp fits over a T bolt with one end resting on the work and the other end on a packing piece. It is very important that the packing piece is slightly higher than the work so the clamp does not bear on the very edge of the work. This tends to push it sideways rather than hold it down and you lose a lot of the clamping effect. If you can, arrange the hole position so there is less distance between the clamp bolt and work than between clamp and packing piece - the hole for the T bolt does not have to be in the middle. That way, more clamping force goes into the work.

Second thing is to make sure you are clamping both work and spoil board. Sometimes you can end up with a clamp that is tending to lift the work off the spoil board. For example, if I am supporting a long work piece on a piece of MDF at each end, I make sure my clamps are between the supports and not outside them.

Generally, try to space your clamps as far apart as your cut allows, and make sure there isn't any wood dust between bed, spoil board, and work. Like trying to clamp to a bed of ball bearings otherwise!

As an example, I was cutting some counterbores and through holes in MDF window board material yesterday - 25mm fairly dense MDF. Ok, light cutting loads, but each 1.8m board just sat on two MDF support pieces to give clearance for the cutter to pass through, and were held with a single clamp. No problem at all. MDF can work fine as spoil board material!

[Josh_BCF]

my bed: https://i.imgur.com/jx3NAJu.jpg
Clamps: https://i.imgur.com/VkjFngU.jpg (I did have 3 but cut one down to try and bolt it therough spoil board - so I'm currently looking to replace them all tbh - they are well used)

Thing with using my router to make the spoil board with counter sunk holes and what not is how would I be able to line up the tee slots, and I need the whole sheet for the signs in cutting out really. With clamps I still get a lot of waste as I have to set my work piece origin after them.

Really I just need more clamps - or at least decent Tee bolts for my clamps to sit in.

[Clive S]

Josh do you have a pic without the spoil board on?

[Josh_BCF]

No sorry - my slot things don't go all the way up, must be less than 4ft because my spoil board atm peeks over the edge by about an inch.

The way I had it set up was 2 clamps closest to me and one at the back with wood under the clamp... not very safe - as I'm the obly one trained with using it - trying to find a user friendly way for people to set the bed up when I'm on holidays and such.

[Josh_BCF]

So I didn't bother fixing a spoil board to it and instead am using 1 sheet of 18 mm MDF and then my cutting board on top of that (Which is another 18 mm sheet of MDF) - but now for some reason NCStudio keeps throwing up an out of limits thing when I try to set it with the mobile calibrator....

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