spoil boards

I would like to hear what others are using for drill patterns in spoil boards. We are using 3/4" lightweight mdf. We typically find the low point of the surface and then machine the entire surface flat. We drill drill eight rows of holes 3/8 deep. This sort of works but we do not get great hold down. What would make it better more holes, deeper ones?

Thanks,

Morgan

Been trying to get Robert to chime in on this, but allot can be said about the vacuum/suction source too. Here is a link that he shared with me ....
http://www.talkshopbot.com/forum/showthread.php?t=545
He also mentioned being willing to making up kits [completely wired and setup with motor] for folks who may be interested. rob is using two
motors wired together set up for 220v, but single motor set ups are an option. A stronger vac source will definatley give you better hold.

Your spoilboard sounds to be normal 3/4" MDF, although 1/2" is fine too. You can run without a spoil board too. Use gasket foam [weatherstrip]
in the channels to localize cut projects to that zone. Cut custom channels into the plenum to seal off specific cut programs regularly.

With your automatic bit hieght setter you worked up, you should be able to run sans spoilboard most effectively, without ruining the plenums. They are MDF
as well and can be resurfaced and/or replaced as needed without much expense.

MC

We have been using mechanical hold down for our cores but need the vacuum to work with base. The base is held down with the vacuum until it is about 75% cut out and then it starts to lift. It would be great to hear more about vacuum systems people our using we have not been sure what type of motor to use.

Thanks,
Morgan