So I needed to put 2.75" and 3.25" holes in 1" thick plate. I didn't want to spend all day trying to machine that big of a whole start to finish on the lathe, so I instead decided to use a hole saw to get 2.5" out of the way, and then use the lathe to finish up the project. I had used big hole saws on 1/4" plate before, and it works fine. Usually I will drill most of the way though on one side and then flip the part to finish it off..
I didn't have a lot of success on 1" plate. I have a big drill press and used the slowest speed, also used tons of oil. It cut about 3/16 or 1/4" deep pretty quickly and then bogged down there. After what seemed like an hour of cutting, lifting to clear chips, cut, lift to clear chips etc. I finally got the first of 4 holes done. So deciding that the issue was the chips had no where to go once the teeth were too deep I decided to try a new tactic. The hole was supposed to be 2.5" diameter so 1.25 radius. I drilled 1/4" holes with their outside edges right at 2.5" giving the chips a place to go as I cut. With drain holes, the hole saw cut through the 1" plate in a few minutes. It took time to drill the 1/4" holes, but the overall process was at least twice if not 3 times a fast as trying to just cut the plate with the hole saw alone... Not required for thinner plate, but if you need to make a big hole in thick plate, you might want to try this technique...
I didn't have a lot of success on 1" plate. I have a big drill press and used the slowest speed, also used tons of oil. It cut about 3/16 or 1/4" deep pretty quickly and then bogged down there. After what seemed like an hour of cutting, lifting to clear chips, cut, lift to clear chips etc. I finally got the first of 4 holes done. So deciding that the issue was the chips had no where to go once the teeth were too deep I decided to try a new tactic. The hole was supposed to be 2.5" diameter so 1.25 radius. I drilled 1/4" holes with their outside edges right at 2.5" giving the chips a place to go as I cut. With drain holes, the hole saw cut through the 1" plate in a few minutes. It took time to drill the 1/4" holes, but the overall process was at least twice if not 3 times a fast as trying to just cut the plate with the hole saw alone... Not required for thinner plate, but if you need to make a big hole in thick plate, you might want to try this technique...
