After this incident I weighed this chunk of cast iron cylinder head and found that it weighs 16-1/2-lbs. I was positive that a drill press was not going to snatch this much iron out of my hand, especially with a 5/16"-diameter drill bit! Yeah, that was stupid!
Click image to enlarge

A Close Call at the Drill Press

Or I overestimate size once again!

Text, photos and video by Tom Hintz

Posted – 2-25-2011

I have been working with metal in one form or another nearly all of my 60-some years. I really do understand the concept of a drill bit locking onto the piece it is drilling, particularly when it first begins to break through the other side. I also know that possibility makes it dangerous it is to attempt holding an object by hand while drilling it, particularly small pieces. Consequently I have never had a close call when drilling a small object.

Yesterday I proved to myself that size really doesn’t matter and that I simply do not understand the power of my Powermatic PM2800 drill press and its 1-HP motor. It is important to remember that Powermatic rates their motors using a continuous duty cycle which tells you the real power available all of the time, not just in bursts. I understand that power rating, honest. Until yesterday, I had not had the chance to witness such a graphic depiction of the capabilities of that single but very real horsepower.

The Task

You will never catch me holding a small piece by hand while drilling. I know that is why small vises (left) were born. The good news out of all this, in addition to my pointing this mistake out to everybody is that I got away with only this little nick.(right) I don't have a clue why that is all that I got but it was.
Click images to enlarge

I was doing a review of the KD 40-piece Gearwrench Tap & Die Set and wanted to tap a hole in cast iron. I had a section of a cast iron racing head left over from my magazine days and had already drilled and tapped it a couple times without issue before making the video. I was confident that the 16.5-lb mass (I weighed it later but it always felt heavy) of my chunk of cast iron would prevent it from taking off on me. I actually thought that the drill bit would break before the iron moved. Incidentally, I was using a Milwaukee 5/16”-diameter Thunderbolt bit that proved to be way stronger than I thought.

The drilling was going fine, the cast iron sat motionless on the table as the drill was working effortlessly at about 500-RPM. Then it broke through to an open space and the bit locked on the cast iron.

It’s Gone

Before I could hear or see any difference in the drilling process the chunk of cast iron was jerked out of my hand and made about three quarters of a revolution before it finally stressed the bit enough to snap it off. Fortunately for me the Milwaukee Thunderbolt bit held on until the iron was aimed towards the back of the drill press. At that point the bit snapped and the iron took off, bouncing off of the drill press column before flying to my right where it hit a bunch of stuff stacked against a large cabinet. That slowed it down enough that it dropped to the floor where it rolled/bounced enough to move my photo lights and the camera tripod.

Video Tutor

I shut the press off and looked at my hand that was holding the now departed iron because it hurt some. I was concerned that my hand was not hurting too bad as that has in the past meant that I was really messed up. Fortunately with the exception of one small, shallow nick I had escaped unharmed. Chalk that up to pure dumb luck.

Conclusions

Yes, I know I should have clamped the piece down. And yes I now understand that my concept of big enough isn’t big enough. And yes, I know that this was an idiot thing to do. My new goal in life is to never repeat this bit of stupidity. I decided to show this dumb mistake so you all know that I did it which will help prevent me from doing it again. I also hope that seeing my venture into stupid-land will make someone out there think BEFORE they get hurt.

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