I just wanted to know if there is a best practice for drilling on a lathe.
I know to start with a center drill to get the hole started. After that should I just chuck up the bit size I want and go to town or should I start with a smaller bit and then size up in steps?
Also, my assumption is that drill bits are more of a "close" but not perfect size hole? If I wanted a perfect hole I would use a reaming tool correct?
The guys have given you excellent advice - start with a spotting drill if you can and if you need to drill a large hole then using a pilot drill that is sized to span the web of the main drill helps. It helps because the center of a drill does not cut; it locates the drill but it requires more pressure to move it through the cut and the pilot obviates this need.
The problem with using pilot drills is that they tend to be small drills that must also be pushed through the cut and the pressure tends to bend them and make those small drills wander. This will lead the main drill that follows to follow the same wandering path. For this reason, if you need an accurately placed hole it is often better to spot and follow with the main drill. You will also find the main drill will also produce a more accurately sized hole because it is larger, stiffer and is also not bouncing around inside the hole.
All drills deflect, even large ones. To minimize deflection, use enough pressure for them to continuously cut but no more than that. A properly sharpened drill will output equal sized curled chips from both flutes and you should see these chips continuously moving. If they stop moving, raise the drill and clear the chips. When you go back in, use more pressure initially to get the drill past the work hardened surface and then watch for the chip flow. With large drills, slow the speed way down and increase feed pressure to keep chip production going. This maximizes the cutting action and minimizes heat production. Done well, a 1/2" drill will only feel slightly warm immediately after the cut.
If you need an accurately sized hole or a hole with a good finish then reaming will do that. However, it may not be a straight hole. Reamers follow the hole so if the drill produced a wandering hole then the reamer will produce an accurately sized and finely finished wandering hole. If you need an accurate, straight and properly sized hole with a fine finish then you should drill the hole, bore it straight and then ream it. The problem is that quite often we do not have the right sized reamer, in which case the only option to get an accurate hole is to bore it.
Keep in mind that drills are like all cutting tools - if they chatter, slow down the speed and increase the feed. Since both flutes must cut, both flutes must be sharpened identically. Unless you are good at drill grinding by hand, buy a Drill Doctor or some other machine/jig to aid you.
Making a hole is easy. Making a straight hole is a bit harder. Making a straight accurate hole with a fine finish is much harder. And then you have to make sure its located in the right place! Fun, isn't it?
Guess the forum is working well.