Tapping a Straight Hole With the Aid of a Drill Press

This is a description of a simple operation that might make tapping holes a little easier! Ever wondered why your taps have a little chamfered hole in the top? Read on and learn

tools and supplies:
material that needs a tapped hole
drill press
center punch
hammer
center drill
tap drill ( sized to tap )
chamfer
live or dead center
tap
tap handle or wrench
tapping fluid
safety glasses

Center Punch Hole Location and Center Drill

Using your center punch and hammer locate where the hole is to be tapped. Centet drill hole location ( sorry forgot pic ) I cannot stress enough the importance of a centet drill when hole location has to be accurate!!

Drill Hole With Appropriate Drill Size

Now drill your hole with the drill you selected. There are charts available for this. There is also a formula for this as well.

Chamfer Your Hole

Using your chamfer tool, chamfer the hole. I like to go slightly larger than the major diamter of the thread to be tapped. This gives a nicer lead into the thread with no burrs. It also looks better.....

Line Up Tap

So at this point install your live/dead center in drill press. Install tap handle on tap. Line up your taper tap with drilled hole. Now the tricky part. Bring your live/dead center down on the little hole in the top of the tap. Now you should be lined up dead cenrer on your hole.

Start to Tap

Ok now apply some cutting fluid. Apply pressure to drill press and rotate tap handle. If you dont have a tap handle any wrench will work with this method. For every rotation of 360°of cutting action rotate tap reverse 1/4 turn to break off chips. If this is not done broken taps may be in your future!!!
If you are tapping a blind hole start with a taper tap and once full thread engagement is achieved switch over to a bottoming tap.

Finish Up.

Once you are finished tapping the hole clean out all the chips and cutting fluid. If done correctly you should have a nice straight tapped hole.
I use this method quite frequently when I have to tap very large holes. If everything is locked done to bench tapping a 3/4" npt hole is pretty easy.
Hope this helps make life a little easier
Enjoy