Tapping a Straight Hole With the Aid of a Drill Press





Introduction: 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

Step 1:

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

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



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Many of my taps have a conical tip not a centre hole in the end. I took a piece of round bar stock and, using a centre drill in the lathe, drilled a shallow hole with taper into which the pointed end of the tap will sit and centre. I put that into the drill chuck instesd of the

I also just put the tap directly in the chuck. On my el cheapo drill press, variable speed is achieved with a belt and two stepped pulley wheels. This allows me to just remove the belt and turn the shaft by hand (holding on to the chuck) when tapping. Consistent with my machinist skill and sophistication levels, I suppose I could grasp the tap shaft between the chuck and the tap threads with a needle-nosed Vice-Grip if necessary.

that is a great way as well. try leaving all belts in place and use your chuck key as leverage. this ible was meant for taps too large to fit into chuck.

Thanks for a great Instructable. After I have tapped the hole, what is a safe and easy way to remove the cutting oil from a thru hole? from a blind hole?

I just point hole away from me and blast with shop air.

That sounds good. Do I have to worry about loose chips flying about when I use air? Especially with a blind hole. I guess I could just put a rag over the hole and then blast away. Thanks.

The machinists that taught me would tell you to float it out with oil, never compressed air. In fact if they caught you with an airline next to a machine they would ask you if you were a machinist or an auto mechanic. You would get the day with a hand file to think about your answer. Never, ever, use compressed air in a blind hole. You know two things going in - one, there are razor sharp pieces of metal in there and two, the only way out for the air is back the way it came in. The one time you forget to have on your safety glasses is the one time you get a trip to the doc. Even if you always have them on you are still talking about spattering oil and metal everywhere under pressure. Personally, on large holes I take a bit of soft copper wire and bend it into a U and then bend the tips out and then chase the threads down with the bent out tips. On smaller holes I use a spray bottle filled with oil (But didn't you just say...) yeah, but you are talking a few psi vs whatever your compressor is set at (90?), it is a world of difference.

this is all true. there is a very good reason vintage machinist toolboxes have little mirrors in the lid.

I can see clearly, now. Thanks very much!