I'm on the first step of building my 3 axis Lindberg skull from kit from Graveyard Skulls. I'm using a 3/32 bit and got one hole drilled in the plexiglass plate. The next hole the bit gets stuck and breaks off in the plexiglass. I filed it down and started another hole and the same thing happens. Is it bad bits, wrong type of bits or is there a trick? Will these bits embedded in the plexiglass affect anything?