Checking a drill bit for warping

[Herb G]

How do you check your drill bits to see if they are bent or warped?

[barryvabeach]

roll them on a flat surface?

[jlanciani]

Put it in a drill press, turn it on and observe...

[castguy2003]

Ditto to rolling on a flat surface

[Steve N]

Ditto to rolling on a flat surface

Yep

[daddo]

The best way is to use the drill press to know if it is running true. Rolling it on the counter won't show very slight defects.

However you have to check your drill press accurately for runout and fix that problem first. A drill may roll fine but be off in the press. The cause could be a slip in the chuck at one time causing a little spur on the drills shaft- file that away or it will never run true. Even filing it may not return it to specs.

It depends on what you expect as "accurate"- .002", .003", .010"+ ?

For the most part, I keep the "best bits" stored for accurate cuts and use the cheaper ones without worry about wobbling (within reason) for most hole cutting.

[Steve N]

The best way is to use the drill press to know if it is running true. Rolling it on the counter won't show very slight defects.

However you have to check your drill press accurately for runout and fix that problem first. A drill may roll fine but be off in the press. The cause could be a slip in the chuck at one time causing a little spur on the drills shaft- file that away or it will never run true. Even filing it may not return it to specs.

It depends on what you expect as "accurate"- .002", .003", .010"+ ?  

For the most part, I keep the "best bits" stored for accurate cuts and use the cheaper ones without worry about wobbling (within reason) for most hole cutting.

Thats interesting. What do you use to measure that run out, and then to measure the bit in the chuck? I see guys talking about their drill with a run out of.......... I always just assume they are measuring the quill shaft, because measuring a bit is pretty hard to do, unless you get one reading and accept that as Gospel.

I grew up with 4 guys who now are machinists, own tool shops. They need to know, and their $$$$ goes toward good chucks. Even pretty expensive chucks will grapple the bit at different angles every time you chuck a bit. If you have a dial indicator to check for run out on a stand, you can check this yourself by simply chucking and re-chucking the same bit 10 times. If your indicator is worth salt it will give fine enough readings that you will likely see 10 different measurements. Bit didn't change. End of this is it's wood, and tolerance doesn't have to be exact, cause the darn wood moves. It comes down to how many hairs thick you will tolerate your hole being off center, or out of round.

BTW, all 4 of my buddies roll a bit to check for true when they are doing woodworking, home repair, or drilling for whatever reason at home. Because at home they know they don't have the equipment to check it like they would at work, and they sure don't have the chucks they do at work either.
 
 

[Arlin Eastman]

The best way is to use the drill press to know if it is running true. Rolling it on the counter won't show very slight defects.

However you have to check your drill press accurately for runout and fix that problem first. A drill may roll fine but be off in the press. The cause could be a slip in the chuck at one time causing a little spur on the drills shaft- file that away or it will never run true. Even filing it may not return it to specs.

It depends on what you expect as "accurate"- .002", .003", .010"+ ?  

For the most part, I keep the "best bits" stored for accurate cuts and use the cheaper ones without worry about wobbling (within reason) for most hole cutting.

Thats interesting. What do you use to measure that run out, and then to measure the bit in the chuck? I see guys talking about their drill with a run out of.......... I always just assume they are measuring the quill shaft, because measuring a bit is pretty hard to do, unless you get one reading and accept that as Gospel.

I grew up with 4 guys who now are machinists, own tool shops. They need to know, and their $$$$ goes toward good chucks. Even pretty expensive chucks will grapple the bit at different angles every time you chuck a bit. If you have a dial indicator to check for run out on a stand, you can check this yourself by simply chucking and re-chucking the same bit 10 times. If your indicator is worth salt it will give fine enough readings that you will likely see 10 different measurements. Bit didn't change. End of this is it's wood, and tolerance doesn't have to be exact, cause the darn wood moves. It comes down to how many hairs thick you will tolerate your hole being off center, or out of round.

BTW, all 4 of my buddies roll a bit to check for true when they are doing woodworking, home repair, or drilling for whatever reason at home. Because at home they know they don't have the equipment to check it like they would at work, and they sure don't have the chucks they do at work either.
 
 

You are both right.

As a machinist for 20 + years I have always checked that my drill press tolerance and if strict tolerance is needed I measure the bit on the drill press for run out, however, the other times I rolled the bit on the marble surface to see if it was out first.
Also not all drill bits are made equal so be carful what you buy.

Last for drilling wood if a bit is .010 out that is no problem nor even .025 out since all bolts need space to be inserted and wood moved several thousands also.

[BloomingtonMike]

You guys don't have a Woodpecker limited time only tool drill warpage plate - only $249 pre order only??

[mike4244]

Herb, you may be able to straighten smaller diameter drills. I usually have good luck with drills 5/32 " and under by drilling into a piece of scrap hardwood. Heat is created as you drill down and this will straighten the drill. I install a drill in the DP. Then run the bit up and down into new holes until the drill looks straight with no wobble. The larger the diameter the longer it takes . I keep off cuts of cherry and persimmon for this purpose. Any reasonably hard wood will do,even junk wood from a pallet.
mike