How to Use Countersinking to Blind Mount a Sculpture
Kevin is working on the base of his functional sculpture Lady Bugme, a commission for a woman who is putting it in a high-profile location in her back yard. The sculpture will sit on a steel plate on top of a sump pump, which is used to drain off any excess water that flows off the yard's hard tile, concrete seating, etc.
For the base, Kevin used 1/8" steel plate and drew outlines of her feet on it, then he tapped the feet themselves. He then countersunk holes in the bottom of the plate so the Allen head, grade A bolts he screws in from the bottom are flush with the bottom of the steel plate. That way the sculpture will sit flat on top of the sump pump cover.
Next Kevin explains more about what a countersink is and how it works, and shows what it looks like. It has an angle that allows you to cut away the metal in the shape of the head of a bolt, using its forward cutting edges, so it can fit flush with the metal surface.
You use the countersink pretty much like a drill. You can use it in a handheld drill, a drill press and even in a mill, depending upon what you are working on. In this case, Kevin is going to use the countersink to fix a hole in which the edges raised when he was countersinking from the bottom of the steel plate. To allow Lady Bugme's shoe to sit flat, he's using the countersink to remove the ridge and slightly chamfer the hole. It just takes a quick couple of revolutions with the countersink to do the job.
Then Kevin explains why a countersink is better than using a drill bit for the same purpose: a drill bit only has two cutting surfaces, while a countersink has three. So a drill bit can chatter a bit, making the hole a little rough and uneven. Kevin says, however, that you can use a drill bit in a pinch - he has, many times - but the countersink does have advantages.
His countersink can be used for a lot of different sized holes, from 3/4" down to a point. It's a versatile tool that can be used on a broad range of materials, hole sizes, and it doesn't take up much room or cost much. Finally, Kevin gets back to assembling the sculpture.
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