[woodnthings]

I see a small set screw by the bolt

That may be the adjustment for level, I donno?
See post by handy-dan:
http://community.woodmagazine.com/t5/Tools-and-Tool-Buying/How-to-level-a-drill-press/td-p/320517

I've never seen nor heard of shims to level a drill press table. Usually there is just a large, bored hole on the casting that has been machined perpendicular to the table face.
That bolt head does look difficult to access. Use a high quality wrench when attempting to loosen it , not a cheapie that is sloppy on the fit.
If you round the hex over you are in big trouble. :laughing:
When loosening a bolt, a sharp rap is always better than an increasing pressure applied. A snug fitting wrench and a rap from a dead blow hammer should do.
Grizzly has online PDF manuals and you should look yours up to see how it's designed.
http://cdn0.grizzly.com/manuals/g7944_m.pdf

 

[woodnthings]

Ok I get it

The table can "tilt" so the location pin is used a t 90 degrees and possibly st 45 degrees to maintain those.
I'd bet that needs a 3/4" open end wrench on a 1/2" bole.... :blink:
Since it's an import, it may also be a 17 mm metric... :blink:
One you loosen the large bolt, find the 90 degree location by applying pressure inwards to the pin until it slips into the hole. Then tighten the bolt. It's meant to be used frequently since the pin the is means of registration, however it is not very easy to get to.

My old Craftsman has the same system for tilting the table.