Can I use MDF as a spoil board when cutting aluminum?

Often times when cutting aluminum you will need a spoil board under the aluminum, especially when you are cutting all the way through the material.  MDF is a very common material to use as a spoil board for the following reasons:

• There is no grain so it cuts the same in any direction
• It is usually pretty flat
• It cuts easily so when your bit goes through your work piece, there is no additional strain on it when it makes contact with the MDF
• It is easy to find and relatively inexpensive.

Some things to be careful of when machining aluminum with an MDF spoil board:

• Make sure the MDF is secured well to the machine bed
• Make sure the Aluminum is clamped tight to the MDF/machine bed – if it is not you will get vibration, chatter, poor cut finish, and can possibly break your cutting bit.
• You can not use any lubricant when you use an MDF spoil board!  It will swell and expand if it gets wet.  So using spray or mist coolant or oils like Tap Magic is not recommended.

An alternative spoil board that we use is acrylic.  Acrylic is hard, flat, easier to machine than aluminum so it will not strain your machine and if you want/need to use lubricant, then you can without worrying about it damaging the spoil board.