balindamood

I now have a granite alignment table (1.75-inch granite slab from a billiard table...ugly, heavy, but flat).

Anyway. I need to drill a 1-inch hole in it to attach a BB boss. How do you drill a 1-inch hole in granite (preferably without cracking it)??

Alan Edwards

Hay Balindamood, well before the bust of '08 I was a granite fabricator. What you need is a diamond core bit. Harbor freight has them some times. Hay give me a PM, I have one in a box.

rafi

It's a good idea to drill a pilot hole with a smaller bit, and then go in with the bigger bit. Also, most likely, if you go in from the top, when you break through the bottom you're going to chip out a hunk of granite. It doesnt matter too much, but a way to avoid that would be to drill the pilot hole half way in from the top, measure really really well it's location on the table, and drill the other half of the depth of the table from the bottom, then repeat with the bigger drill bit.

Also, for a 1" threaded rod for your post, you'll want a slightly larger bit.

And try not to breath the dust.

Smudgemo

I drilled a 1" hole through mine for a 7/8" bolt using a diamond core bit. I'd drill until the bit was mostly filled, then break out the plug with a screwdriver. I also used plumber's putty to contain water to cool and lube the bit while eliminating dust issues. I probably should have drilled just enough for a threaded insert, but I didn't know they existed at the time. I wasn't sure of how close to the edge I could go, so I called Standridge and they said 1/2", I think. I went more just to be sure. Since a pool table is thinner, you probably need to stay further from the edge, but I'm just guessing.




The photos don't seem to be showing up, but you can see the somewhat lame setup here:
https://www.flickr.com/photos/smudgemo/5064992682/

Alan Edwards

Well I'm glad to see a lot of good suggestions. The pilot hole is one I never used but I used a little drill press that I put on the counter to drill the hole. Making a little dam is what I did also and a sprayer to keep the whole thing cool. If you don't go all the way through don't use the bit to get the plug out, thats how one of my guys broke one of my bits. With a drill press even the broken bit drills holes just fine. With kids I used play dough to build the dam.

balindamood

All good suggestions. The slab is not on the table carcus yet. I was going to drill on the floor, backed with a piece of plywood or 2-by-something to try to eliminate break-out. The slab is 3.5x4.5 feet, and I left 4-inches of lip around the edge fo the table for clamping. The 1-inch threaded rod will actually go into the top of one of the legs to try to keep any prying forces on the slab to a minimum. I pulled the BB clamp off a spare Park FRS-1 (diagram below), so it is a matter of drilling one of the 4x4 legs to accept the shaft, plus some counter sinking to put a nut and the mother-of-all fenderwashers on the bottom side to support it. The drilling of the hole through the slab is the one part I have not fully gotten figured out yet.

Live Wire 

Granite surface plates use are usually much thicker than what you're using and cold-setting is not recommended on them....it would be a good idea to not do any prying/bending on yours.

balindamood

Agreed. I am running the long end of the bolt for the BB thingy into one of the table legs, but do not expect the granite to be thick enough for cold setting without cracking it. It is more for alignment measurement and futzing about.