Tap and Die Question

You should be able to find a 1/4-20 bottoming tap at your local Ace or True Value store. It's a pretty common size. Sometimes it's easier to just go put eyes on the thing. Also, you may need to start it with the normal tapered tap just to get some light threads started.

 

Why a bottom hole? Why not a through hole, far simpler to tap. A bottoming tap is a b1tch to start, usually you start with a tapered tap and then finish with a bottoming tap.

 

Take A tapered tap also known as a gun tap and take to belt sander. Lightly grinding away the tapered tip do not burn use water to cool at intervals. Now you have a bottoming tap that will actually tap threads all the way to the bottom. Always use a tapered tap first and bottoming tap second to assure your threads are straight.