Learned something about drilling today

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jpfalt
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Joined: Sun Jan 05, 2003 12:55 pm

Re: Learned something about drilling today

Post by jpfalt »

Concerning the prick punch, I learned to scribe two intersecting lines at the hole location. Then you place a prick punch tip in one of the scribe lines and follow the scribe like a phonograph record groove until the tip drops into the intersecting scribe line. You can feel it. Then you hit with a hammer to make the prick mark. To be old school true, i would set the tip of a center punch in the prick punch mark and restrike heavily to center punch. If my drills were not center cutting, I would use a 1/8" bit or a #5 center drill and let it drop into and center up on the center punch mark and finally go into the hole with the final drill, letting it drop into the 1/8" hole or center drill mark.

I also learned that with larger drills that did not have a split point, things went much easier if I first drilled the hole with a small drill the diameter of the width of the chisle point on the larger drill. I was taught that about 80% of the force required was to push the center of the drill through the metal and to push that metal sideways into the flutes.
John Hasler
Posts: 1852
Joined: Tue Dec 06, 2016 4:05 pm
Location: Elmwood, Wisconsin

Re: Learned something about drilling today

Post by John Hasler »

jpfalt wrote:Concerning the prick punch, I learned to scribe two intersecting lines at the hole location. Then you place a prick punch tip in one of the scribe lines and follow the scribe like a phonograph record groove until the tip drops into the intersecting scribe line. You can feel it. Then you hit with a hammer to make the prick mark. To be old school true, i would set the tip of a center punch in the prick punch mark and restrike heavily to center punch. If my drills were not center cutting, I would use a 1/8" bit or a #5 center drill and let it drop into and center up on the center punch mark and finally go into the hole with the final drill, letting it drop into the 1/8" hole or center drill mark.
That's exactly what I do. It's not real precision, but the resulting holes are not visibly misaligned and it's adequate for assembly holes with free-fit clearance.
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seal killer
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Joined: Sat Aug 18, 2007 10:58 pm
Location: Ozark Mountains

Re: Learned something about drilling today

Post by seal killer »

All--

As you might know, I am heavily involved in other matters at this time. However, I am very glad I took time to read this thread!!!

--Bill
You are what you write.
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