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Mark's Web Site
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Date: 2-22-2014
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Number of Hours: 2.00
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Manual Reference: 09-02
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Brief Description: Countersink 101 (09-02)
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Countersink 101 (world according to MJ):
OK, I think I figured the issues I was having with the countersinks. There are 2 challenges with countersinking:
First is that we are putting countersinks in very thin sheet metal and as a result the chamfer almost or in some cases completely goes through the thickness of the metal. This causes the hole at the opposite side of the hole to get larger as the countersink is driven deeper. The countersink tool has a pilot tip on it to keep it centered, but this becomes useless once the far side of the hole (small end) becomes oversized, which allows the tool to walk.
The second issue is that either the countersink, the micro-countersink tool or the drill can have a slight wobble (eccentricity) which can enlarge the countersink holes, near and far side. When you hold the micro countersink tool firmly it translates that wobble right to the work piece, which enlarges the hole.
To resolve these issues I did two things. First I used a scrap part underneath (with the same size hole) to increase the thickness of the hole and allow the countersink pilot tip to maintain its center. Second I originally held the micro-countersink tool rigid, but realized that it translated the wobble to the part and enlarged the hole, so instead, I let it wobble, which allows the tool to rotate around the true center of the hole. In addition I went back to using the cordless drill since I could control the speed and slower works better. As a result, the countersinks have been working out well.
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Using scap part as a pilot hole to keep countersink centered
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countersink workin much better with additional thickness for pilot
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16 perfect countersinks and no issues
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