[radioactive]

OK, so I'll admit I purchased a cheap china made drill chuck. Most everything else I've bought for this hobby has been high quality as it always works out to be cheaper in the long run. However, I'm out of funds and found that I didn't have a drill chuck and needed one. Here's what I got...

China drill chuck

I put it together and mounted it on the machine. Drilled about 20 holes and it worked fine. Swapped the bit for a larger one and was drilling a hole (.25) in a block of 6061 1" deep. When it tried to retract to move to the next hole location, the taper had came loose and the drill bit was still in the hole 1/2" when it tried to move in the Y direction. The bit flexed quite a bit before I got the machine stopped.

So my question is what went wrong? How hard do you need to seat the taper so that it doesn't come loose? Should it be dry when you assemble it?

I'm glad the whole thing didn't fall out when it was rapiding over (at 4000 rpm)

[djr76]

http://www.jacobschuck.com/drill-chuck-install.asp


If it keeps popping loose, then you either have a junk chuck or taper. I suspect the cheapo chinese made chuck.

[Geof]

Clean both parts of the taper really well, you don't want any oil or dirt on them when you put them together.

Assemble the chuck and arbor and drive it home with a dead blow or lead hammer.

Now put a pencil mark right at the end of the taper as a reference and squeeze everything in a vise to push the arbor deeper into the taper. It should move a little bit without a really large amount of effort applied to toghtening the vise; maybe 20lb force on the end of the vise lever.

Don't reef on it like a gorilla if it shows no sign of moving.

There is no guarantee the chuck will not come loose again but it should be less likely.

[Donkey Hotey]

I've got some of that guy's stuff and I can tell you that it's mostly junk. I bought a set of 5 hand-tightening chucks from him and every one is like you described.

I found that putting a bit of lapping compound on the taper and lapping the joint helped. Of course, you have to clean it really well when you're done.

After that, Geof's methods sound like a really good way to minimize it dropping off again.

[dertsap]

if it does come loose again then you could spray some machinist blue on it then smack it together again , i've done it many times in the past with sloppy tapers and it works most of the time

[MrWild]

Get a better one. The one I got from him had problems with the NMTB30 not drawing tight because the hole wasn't tapped deep enough for the draw bar. Using a different adapter, the chuck kept popping it's taper. A total waste of money.

[BobWarfield]

Shrink fit them.

After carefully cleaning all surfaces, heat the chuck a couple hundred degrees in the oven. Freeze the taper in the freezer.

When they reach temperature equilibrium (aka, after you finish a cold one), it's time to put them together.

Grab a cutting board to protect the counter, put on an oven mit to protect your hand, take the chuck in the mit and the taper in the other hand, chuck on top, and bang them down hard on the cutting board together.

Once seated this way I have not had even a cheap chuck come off the arbor unless provoked with too much lateral motion.

I use Lathemaster's keyless chucks. They're inexpensive but well made. The original owner of Industrial Hobbies recommended them to me.

Cheers,

BW

[DareBee]

No matter how you assemble something with an unmatched taper, it will come apart again. You could try a light smear of LocTite bearing retainer before you press it together.

Also - to anyone else reading this post - most of these things mentioned are not proper techniques and are not a good idea.
These suggestions are given under the assumption that the items in question are already scrap and we have nothing to lose by potentially "finishing them off".
The link in post #2 is proper methods.