Thx , i will buy that set when i get paid. i did a hole for my tank a while back uing a similiar bit and it turned out slightly bigger than the bulkhead connection . i had to use silicone to seal up the excess place.
Here is a couple of pictures showing the difference of a hole saw for wood and plastic vs. one for glass or stone. Note that the one for wood and plastic has a drill bit in the center. This keeps the thing from drifting all over the place. Thus a jig is not needed. Since the one for glass does not have a center bit, a jig is needed to keep its location in one central place. The jig also holds water to keep the bit cool. Water is a must because the heat generated will weaken the bonding material in the bit and the diamonds will pop off. No diamonds, no cutting.
And while I am playing Show-n-Tell, here are more pictures:
The first shows the billet cut from a ten gallon tank and my 15g breeder tanks. The breeder tanks are about three times the weight of a ten gallon tank and the glass is a little thicker than double. I love my breeder tanks.
The ugly ass tank in the second pic is one of my breeder tanks. That is how I got them. The guy scraped some of the paint on all of them but didn't scrape a single tank clean. For forty bucks for 120 gallons of breeder tanks, I think I can put the time in scraping them. I have all but two done so I think my raw bleeding fingers will survive.