While I'm here, how about a tip or two to reduce the chance of a broken tap? If you are a trained machinist or mechanic you should already know this. But there are a lot of people on this site working their first mechanical project.
1. Use a tap lube. Tap-eze is a very good one for steel.
2. Use a tap handle. Don't try to get by with Vise-grips. The straighter you can hold the tap, the less chance for breakage.
3. If you are cutting new threads, back off the tap to break the chips after each revolution. After 4-5 revolutions, back the tap out and blow or wipe it off. Blow the chips out of the hole if you have air or use a Q-tip. Squirt some more Tap-eze in there.
4. If you are using it as a "thread brush" on old threads you won't have the build-up of chips but it's still important to use lube and to back off occasionally.
5. If you are cleaning up threads in an area where chips could cause harm, as in an engine block, pack the flutes with axle grease to catch the chips.
