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
tap drill ( sized to tap )
live or dead center
tap handle or wrench
Step 2: 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!!
Step 3: 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.
Step 4: 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.....
Step 5: 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.
Step 6: 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.
Step 7: 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