Those are designed "exactly" for that purpose. Those holes
match the Biesemeyer back rail, which an outfeed table can
be attached.

The Biesmeyer rail is attached with thru bolts and nuts.

Go here for detailed instructions on how to build the
outfeed and bolt sizes....

http://www.biesemeyer.com/print/comm...e%20Manual.pdf

No drilling required......


Roy Smith wrote:

I've got a Unisaw that I want to attach an extension table to the rear of.
There's two holes (approx 3/8" diameter) already drilled in the rear flange
of the cast iron top (it came from the factory that way), but they're not
tapped; just through-drilled. They're a little too small for clearance of
a 3/8" bolt; it would be nice if they were whatever the tap drill diameter
for a 3/8 UNC is supposed to be, but I haven't measured them exactly, so
I'm not sure.