Problem with drill bit

[qquake]

I'm having a weird problem with one drill bit. The chuck keeps loosening when I use it. It's a 12.5mm brad point bit, reduced shank. I'm using it in a full size drill press with a 5/8" chuck, tightened with a key. This morning I had to tighten it several times as I drilled 2" into an acrylic blank. This doesn't happen with any other bits, not even a 9/16" brad point, or a 10.5mm bit from the same manufacturer. Any ideas?

 

[jttheclockman]

Jim that is a stepped collar on there so you need to be sure that the quill is locking down on the thinner section all the way. Also whenever using a keyed chuck and this is an old timer's trick, always tighten down on at least 2 positions on the chuck. This ensures it locks squarely. This goes for drills drill presses chucks on the lathe and so forth. That has stuck with me throughout my career in the electrical field where we use all kinds of drill motors and devices that require keys.

I would also check that the bit is straight. There maybe a bend in there and the whipping action is causing the loosening.

 

[chartle]

Also whenever using a keyed chuck and this is an old timer's trick, always tighten down on at least 2 positions on the chuck. This ensures it locks squarely. This goes for drills drill presses chucks on the lathe and so forth. That has stuck with me throughout my career in the electrical field where we use all kinds of drill motors and devices that require keys.

I've always heard this and usually do this but as I think about it not sure how it makes sense.

The chuck key applies forces on two circular parts of the chuck rotating them in opposite directions. Unless you can show some sort of localized metal distortion that only affects one jaw of the chuck, the forces are spread around equally.

 

[jttheclockman]

Also whenever using a keyed chuck and this is an old timer's trick, always tighten down on at least 2 positions on the chuck. This ensures it locks squarely. This goes for drills drill presses chucks on the lathe and so forth. That has stuck with me throughout my career in the electrical field where we use all kinds of drill motors and devices that require keys.

I've always heard this and usually do this but as I think about it not sure how it makes sense.

The chuck key applies forces on two circular parts of the chuck rotating them in opposite directions. Unless you can show some sort of localized metal distortion that only affects one jaw of the chuck, the forces are spread around equally.

Cliff you are probably right and it maybe more of a suspenders and belt combination thing. But I do remember many times this was the answer to get a bit from spinning in the chuck. It something that stuck with me over the years and it can not hurt so I continue to do it. Today everything is hand chucked. or sometimes just chucked

 

[bswim]

Measure the shank where it's turned down. Make sure it isn't tapered.

 

[chartle]

Also whenever using a keyed chuck and this is an old timer's trick, always tighten down on at least 2 positions on the chuck. This ensures it locks squarely. This goes for drills drill presses chucks on the lathe and so forth. That has stuck with me throughout my career in the electrical field where we use all kinds of drill motors and devices that require keys.

I've always heard this and usually do this but as I think about it not sure how it makes sense.

The chuck key applies forces on two circular parts of the chuck rotating them in opposite directions. Unless you can show some sort of localized metal distortion that only affects one jaw of the chuck, the forces are spread around equally.

Cliff you are probably right and it maybe more of a suspenders and belt combination thing. But I do remember many times this was the answer to get a bit from spinning in the chuck. It something that stuck with me over the years and it can not hurt so I continue to do it. Today everything is hand chucked. or sometimes just chucked

I wonder if its to give you a second try at tightening the chuck. Like after you tighten the first time after a few seconds something stretches or moves and it lets you give it a little more torque.

Kind of like turning it up to 11.

 

[Ed McDonnell]

Make sure the chuck jaws are not touching the shoulder on the drill bit as you tighten. Keep a small gap between the shoulder and the jaws so the shoulder doesn't prevent you getting the bit fully tightened.

Ed

 

[TurtleTom]

Now I'm completely lost on how to tighten a keyless chuck. Do you still turn it and tighten from the other side?:biggrin:

 

[qquake]

I've never heard of tightening the chuck in each of the three holes, but I'll try that next time. I also measured the shank to make sure it's not tapered. Right at the shoulder, it measures 0.437". But right above that, and all the way to the end of the cut down shank, it measures 0.434". Next time, I'll make sure to leave a gap between the shoulder and shank when I chuck it up.

 

[bswim]

I've never heard of tightening the chuck in each of the three holes, but I'll try that next time. I also measured the shank to make sure it's not tapered. Right at the shoulder, it measures 0.437". But right above that, and all the way to the end of the cut down shank, it measures 0.434". Next time, I'll make sure to leave a gap between the shoulder and shank when I chuck it up.

That's most likely your problem. It should be perfectly straight. Rather than having contact the whole length of the chuck you're really only clamping onto the drill in one spot, at the .437". Drill is probably running out as well.

I've drilled 10s of thousands of holes and dealt with countless problems. (21 years as a machinist)

I'd get a new drill and try it out. At work if I saw a shank with a finish like that I'd chuck it into the trash and get a new one.

 

[flyitfast]

I've heard the same thing about Jacobs chucks and try to do it "religiously". Haven't had a bit slip since. I do notice that when I tighten the second gear hole there is still a little bit more to turn so I guess the extra holes are there for a reason.
Along the same lines, I have also found this theory to apply to scroll chucks too. I can always get it a little more tightened when I use the key/wrench in the other gear hole. Again, there must be a reason for that second hold.
Gordon

 

[Hawkdave]

Now I'm completely lost on how to tighten a keyless chuck. Do you still turn it and tighten from the other side?:biggrin:

You could always tighten it from inside.:biggrin:

Dave.