Checking Drill Bits for Straightness

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HarryJ

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I have some Harbor Freight drill bits that may not be straight. I'm trying to salvage them for drilling soft materials. I don't have a granite surface plate. Can the bits be checked in a lathe or mill?
 
HarryJ said:
I have some Harbor Freight drill bits that may not be straight. I'm trying to salvage them for drilling soft materials. I don't have a granite surface plate. Can the bits be checked in a lathe or mill?
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they can be checked in anything that rotates.
the question is how are you going to straighten them?

You will find that you can't indicate them. So it will have to be a visual.
 
woodchucker said:
they can be checked in anything that rotates.
the question is how are you going to straighten them?

You will find that you can't indicate them. So it will have to be a visual.
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I'm not going to attempt to straighten them, just cull them.
 
no problem then.
If they are bent toward the end, you may want to cut them off with a dremel and re-sharpen. Make some short screw size drills.
 
You do not need a granite surface plate. Use a piece of glass, the table of your mill or any other pretty flat surface. You just need to roll it across the surface to see if it is bent. No this will not get you to sub ten thous, But even a kitchen table will get you to a couple of tenths, I bet you can not sharpen that drill and have the point within a tenth.
 
See if they roll on a fairly flat table top. What is more suspect is the way they are ground as the point is often no ground symmetrical.
 
benmychree said:
Just say no to Chinese crap!
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Easier said than done.

At $20 for a set of 1/2 in 1/64, they are impossible to beat. I have a few indexes of American drills and Harbor Fright set for questionable tasks.


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What makes you think they're not straight? Roll them on a flat table or counter-top, you'll see it if they are bent. A drill that cuts an oversize hole is more likely to have a bad grind on the point. Easy to fix. And always remember, a drill is not a precision cutting tool.
 
MrWhoopee said:
What makes you think they're not straight? Roll them on a flat table or counter-top, you'll see it if they are bent. A drill that cuts an oversize hole is more likely to have a bad grind on the point. Easy to fix. And always remember, a drill is not a precision cutting tool.
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I have found many drills at the cheaper end of the spectrum that are quite straight, but the central axis of the flutes is not the central axis of the drill itself.

These drills are very poorly sharpened out of the box and are impossible to sharpen correctly, some are so bad that when sharpened the webb is so far off centre that it is quite obvious that it will not cut a hole in anything. Yes they are chinese. I won't buy them again.
 
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