I.D. Chamfering on a Lathe: When I am facing parts on a manual lathe, I like to use an SNMG inserted tool to do the work. This tool uses a square insert with a negative rake and it works great for facing and O.D. chamfering, but it doesn't work very well for chamfering the I.D. of a small diameter bore. The problem is caused by the thickness of the insert under the cutting edge which will make contact with the trailing edge of the material below the cut. The simple solution is to raise the tool above center just enough to clear the heel of the insert from the material below the cut. This is easily done on a machine with a quick change tool post. Keep in mind that this procedure will slightly alter the angle of the chamfer.

Tap Drill Size: This next quick hit comes from Dale Schafer who is an instructor at Topeka Technical College. The nominal tap drill size (± a couple of thou.) for a straight cut thread is the major diameter of the tap minus the pitch. For example: Let's say you need to determine what drill to use to tap a 5/16-18 thread. The formula is simply .3125 minus (1 divided by 18)*. Simplified, this is .3125 minus .0555 = .257. Another example for tap drill size for a 1"-8 thread would be 1.000 minus (1 divided by 8) or 1.000 minus .125 = .875

* The pitch of a thread is the distance between the crest of one thread form to the next crest so that if we have 20 threads per inch, the formula is 1 divided by 20 which = .050

This also works for metric threads except these guys went ahead and figured out the pitch for us. (What a lousy idea). Example: Tap drill size for M14-2 thread is 14 millimeters minus 2 millimeters = 12 millimeter tap drill size.

Poor Man's Transfer Punch: If you have to transfer a hole location from one part to another and you don't have a transfer punch, the simplest thing to use is a drill bit that is the same size as the hole to be tranferred. Simply slip the pointy end of the drill into the hole until it makes contact with the part to be punched. Gently tap the blank end of the punch with a ball peen hammer, rotate the drill 90º and once again tap the drill with a hammer. Now, remove the drill and the part with the hole and X marks the spot.