Woodworking Tips
Woodworking Tips Index
Modifying a Spade Bit

My grandfather owned an old Stanley brace and bit set that included an expansion bit for drilling any sized hole. That drill bit would have come in handy the other day, while I was working on one of my projects. I was making some wood collar blocks that needed to fit snug around some iron pipe.

But I ran into a snag when it came time to drill the holes for the pipe. I didn't have a bit that matched the 1-1/16" outside diameter of the pipe. So I modified a 1-1/8" spade bit by filing the sides until it was the correct size.

To ensure that the bit stays balanced and continues to cut evenly, it's important to remove the same amount of material from each side. A handy way to do this is to use a nail and scrap block to position the bit, see drawing above. The nail positions the side of the bit 1/32" above the scrap and the clamp holds the bit in place.

Once you've filed one side down to the top of the scrap block, you can repeat the process on the other side until the bit matches the size of the hole you want to cut, see drawing at right. One last thing — I made sure to mark the new bit size on a piece of masking tape that I wrapped around the shaft. Or, if you have an engraver or moto-tool, you can mark it that way.
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