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How to fix spade bits wobbling in drill press? Question
I have a cheap drill press and a set of cheap spade bits. Some of the spade bits wobble, the tip makes a circle of as much as 5 mm in diameter for some of them. Others wobble less, 1-2 mm.
Since they don't all equally wobble, I suspect the problem is the bits not the drill press. Also, I have some regular drill bits (different brands) which do not seem to wobble (although they are shorter as well).
Are there any general things I can try to diagnose or fix this wobble? I suspect one option is "buy tools that aren't bottom-of-the-bargain-bin, cheap junk" :) However, I'd like to understand why it's happening, what it takes to fix if I don't want to buy new tools, and how to detect similar issues in new tools I'm considering purchasing.
1 answer
The bits are either bent, or were made (formed, ground to shape) improperly.
Straightening bent bits is possible in theory, but likely to prove difficult in practice. Assuming you get everything lined up just right and supported in a way where you can bend it back, you have to bend it a bit more than "to straight" as it will spring back somewhat. And if you don't have it lined up and supported properly, it may end up more bent out of line than it started.
If they are improperly ground, there's unlikely to be adequate metal to even attempt regrinding them, and they will also be smaller than the marked size when you are done, if you manage to actually improve the shape with your attempts.
If you are not stuck on an island with nothing but time and some bent or malformed drill bits, junking them and buying better ones is the correct action. Used ones may offer a better return on your money (and time spent grinding to sharpen, if needed) if you make sure to take a portable drill and verify that they spin true before you buy.
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