How to tighten a 3 jaw?

[RVJimD]

I thought I read someplace that you should always tighten a 3 jaw chuck in the hole marked 0? Is that correct? Can someone shed some more detail on this?

I was talking with a friend and the topic came up and we were standing In front of my lathe so I looked. Sure enough it has a 0 mark.



Also, on the Jacobs chucks, are you supposed to tighten all three or is one good enough?

jim

 

[JimDawson]

I have heard this discussion before and IMHO it makes no difference. I have tried it and not noticed any difference in the way the chucks tighten. Some recommend using all 3 holes to tighten, but I have never found a difference. Having said that, it could make a difference if one of the pinion gears or the ring gear were fowled up a bit.

Same applies to drill chucks.

 

[Bill C.]

I thought I read someplace that you should always tighten a 3 jaw chuck in the hole marked 0? Is that correct? Can someone shed some more detail on this?

I was talking with a friend and the topic came up and we were standing In front of my lathe so I looked. Sure enough it has a 0 mark.



Also, on the Jacobs chucks, are you supposed to tighten all three or is one good enough?

jim

Since three jaw chucks are tighten at the same time by a ring gear, I have tighten using one socket. You might get more pressure by tighting each socket.

 

[chips&more]

I was under the impression that you might get and I said “might” have better repeatability in jaw clamping if you use the same pinion. If you have jaws and its parts that continue to have the same force and all, you should have a more constant location of your work/part in the jaws….Good Luck, Dave.

 

[Ken_Shea]

I'm of the same opinion as others here,
"might" make a difference, that said, I always tighten all three because it was beat into all of us during shop class by the shop treacher so it's a habit now and no harm by doing it.

 

[higgite]

I have a relatively inexpensive (cheap is such a harsh word) 4-inch 3-jaw chuck that came with my bench lathe. It does operate smoothly and it fits my needs, but it doesn't have a "master pinion" marked on it. So I ran my own test with various diameter drill rods that I'm confident are as nearly round as my DTI is accurate. I found one pinion that was consistently more repeatable with less TIR than the other 2. I marked that one and have been using it exclusively to tighten the chuck. So far, so good. Of course, it won't exactly center all work pieces like is possible with an independent 4-jaw, but when it's the chuck I'm using at the time, knowing I have the least runout within reason just makes me feel better.

Tom

 

[Cobra]

I use a mark to ensure that each of the chucks goes into the spindle mount in the same orientation each time.
As far as tightening the three jaw, if I am worried about the runout, I use the four jaw.

 

[shoeboxpaul]

For a drill chuck, I was taught to use all three holes. There is clearance in the chuck in order for it to work, and it can sorta wedge on itself giving you the feeling that the drill bit is secure. When you use all three holes, especially on an older chuck, you see the chuck turn just a little bit extra using the second and possibly third hole. This can prevent a lot of drill bits from turning in the chuck. For a lathe chuck, I wouldn't think you would want to hold the material with that much force. Single point turning takes less power than drilling, a drill has 2 cutting surfaces usually with greater contact area.

 

[Micke S]

It depends on the condition and wear of the scroll wheel and the support of it in the chuck. Turning the best screw only can be a major difference for low runout compared to other screws. But if everything is in order turning any or all screws does not improve.

 

[dracozny]

Both the 3 jaw lathe chuck and 3 jaw drill chuck I have I find I need to tighten at least 2 holes, the 3rd is usually pointless. However only tightening one I find the jaws do not clamp properly. Both of them are cheap low tolerance.