tightening a chuck

That's the way I was taught in high school shop class...

Well, same here, but they also told us that glass flows over time and a bunch of other provably wrong stuff. I'm with darkon on this one, I've heard it, I do it, but I've never understood the reasoning for it.

Put it another way - my 3-jaw on my lathe only has one place to tighten the chuck...

snip

In my experience, tightening from all three holes will hold the bit tighter and, if done properly, make the bit run more true. When tightened all from one hole, and not snugged a bit in the other two, I believe the bit is skewed some. Moot point with self tightening chucks, which I like better.

It's always good practice to tighten all the holes in sucession. It takes out any possible slop in the the chuck, gives you the best possible hold. You will commonly find one of the holes seems to tighten things up better than the other 2.

It's mandatory > Here's a question from another newsgroup. Opinions?

You may get away with single-hole tightening on a quality chuck in new condition, but I *always* tighten all 3. You will too as soon as you feel the scroll move more.

GWE

How can it? The two parts you're exerting force on, are the same parts in each of the 3 locations.

Well, yeah, the first one seems to have more effect ;)

Hi dave

Could it be that the teeth on the key have a different leverage on the chuck teeth while in one hole than they do when in another hole?? I always thought the guys who designed the "gear ratio" had it figured out so the teeth engaged differently from each of the three holes.

Jerry

I think it has to do with the fact that the ring with the teeth is not a perfect fit on the chuck body. Tightening the chuck tends to c*ck the ring a bit so it doesn't turn as freely. Moving the key to a different hole pushes on a different point on the ring and frees it up.

Ned Simmons

"Grant Erwin" wrote: You may get away with single-hole tightening on a quality chuck in new condition, but I *always* tighten all 3. (clip) ^^^^^^^^^^^^^^^^ I think Grant has put his finger on it. When you tighten a chuck in one hole, you rotate the geared sleeve, but you also push all the clearance to one side. If the chuck is new and in good condition, this will be minimal, but there will always be some. So, as the chuck tightens, the same friction that holds it closed will hold the jaws slightly off center. Applying the chuck key to each of the holes in succession keeps pushing the jaws closer to perfect concentricity.

Hi Ned

I'd bet you have the right idea. That even makes sense.

Jerry

Yeah I'll jump in here.

I was taught to use all three holes on a jacobs chuck... I agree with the 'coller gets torqued differently' theory...

As for the 3 Jaw lathe chuck, I was taught that since the actuation mechinisim is totaly differet than on a jacobs chuck that it was unnecessary, since the scroll is doing the work not pushers behing the coller...

and yeah, if I'm really worried on the lathe.. I use all three....

I say.... Dad was right.....

--.- Dave

Accuracy is kept with the triple tightening. My Dad told me in the 50's. He got it from three professional (USAF) Machinists who in their spare time built Trains that they could sit in not on.

They worked on the B-36's and other prop machines - later they moved to Jets and one to a not named department that has a bunch of very large antennas..... :-)

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

dark> Here's a question from another newsgroup. Opinions?

You are on the right track. The fit between the chuck and scroll can wear with use. When you tighten one hole it forces the scroll off center, so by tightening all three you have equalized the forces on the 3 holes. Bringing it back to center. Mostly noticeable on older worn chucks. I have seen one chuck so bad the only way it would center up right was to use a torque wrench on each hole. Those who have older worn chucks know that the fit between the scroll and chuck body is bad, and can lightly tap on the chuck jaw and dial in a part in a 3 jaw with an indicator. Then start cutting. As long as you don't do any heavy roughing it will continue to run true. This is a way to get a 3 jaw chuck with only 1 tightening hole in it to run true. This is a different problem from having worn the jaws bell mouth. Which is corrected by grinding the chuck jaws true.

On the day of Wed, 1 Mar 2006 19:06:18 -0500... Ned Simmons typed these letters:

Sounds reasonable to me. I've drilled quite a bit of stainless steel on a Delta 16" drill press were I used to work. At times I was drilling 1/2 " or larger holes in 1/4" to 1/2" thick stainless flat stock. Occasionally I would have the bit lock up and the chuck would keep spinning as the bit broke through the bottom of the steel. Someone I was working with recommended that I tighten the chuck at all

Devonshire

I was talking about a Jacobs type drill chuck, which I think was the subject of the original post, not a lathe chuck.

Ned Simmons

Ok, listen up...you're ALL wrong! I drill up to 300,000 holes a DAY! If a drill moves, we make crap or something else breaks. If a drill wobbles a little, it's toast in an hour, and we make crap. We use 4" breaker bars on chuck keys and blow the teeth off the keys often, we buy 100 keys at a time...it's worth it. Tighten a chuck in hole one until snug, tighten in hole two a bit more, tighten in hole three a bit more yet, then tighten in hole one again just short of busting the teeth off the key. Any procedure other than this and the drill WILL move on us. Surprisingly, chucks last 5 to 10 years.

I didn't see Joe's word yet but THAT would be the final word.

Wow, now that was hardcore !... heheheh. As so many have said, including Dad, tighten at least once in each hole. You don't need to break the teeth on the key, rather apply lighter pressure when drilling if that's the case. In case you're using a handheld drill, a small deviation won't be noticeable compared to the imprecision of the method, but if you're using a drill press it's absolutely necessary to have the bit trued properly.

Yes.

You should consider collets instead of chucks if you're drilling 300,000 holes/day. Chucks are a compromise at best.

Regards,

Robin