Ok so in pictures of vacuum tables I have seen it looks like holes drilled through to the table connected to the vacuum supply. My question is if you don't have the entire table covered with a part, doesn't the vacume just suck through the open holes, how does it hold the part?

Chad

 

You keep scap to put on the table

the table can be cut with a criss cross grid of say 6 mm slots  spaced about 10  20 mm apart the vacuum holes link from bottom of table into these slots
you can then use a rubber type seal that you push into the slots so that it is covered with the work  this sits over the top of it you have to make sure that you have a vac
hole that will draw from this area .

the rest of the holes that are not used you bung up with stoppers  the idea is that you do not have any leaks so that the full vac will hold the part in place

you have to also put seal round any area that you will break thro  so that it will not release the vacuum  while you are cutting 

or  you set  your cut so that you leave about  0.5 mm in the bottom of the cut    with plastic this can be cut with a knife after   

if you are doing a lot of jobs  sometimes it pays to make up a spoil board with all the seals in the right place and mount this on top of the table with screw fixings
you have to seal between this and the table as well

regards Bill

Brian, Bill, 

Thanks.

Ok I that is what I was guessing, I just didn't know if there was some high tech solution that I wasn't aware of.

thanks again

Chad

you cover the entire table with a piece of mdf board
the vacuum sucks though the fibers of the board distributing the vacuum equally among the holes
no need for plugs or scraps
however some folks will install sectional shut off valves to increase suction in specific areas
i have a 5' X 10' table and use a 10 hp Fuji blower/vacuum from grainer with great success 

on a side note use the router to "plane" the top of the board to insure an equally distance to the tool