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Tightening the Chuck

Kent Reisdorph

Kent Reisdorph

Joined
Sep 19, 2023
Messages
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Location
Columbia, TN
I have observed turners doing a couple of things with chucks that make me wonder.

1. I see turners tightening the chuck with all their might. That doesn't seem necessary and can actually make the tenon weaker.
2. After they tighten the chuck with all their might, they rotate 180 degrees it and tighten the opposite pinion. Why? Habit?

Curious what you all think.
 
I tighten until "firmly snug" (I don't want to crush any fibers), and yes, I do rotate it to the other hole and give it one last try. Why? I don't know. I do the same with my drill press chuck, all three holes see the key, because my high school shop teacher told us to. There may be a mechanical rationale, but I don't know it.
 
all chucks have a little bit of play in the tightening ring. Because of this, the ring can bind up, making it seem tighter than it is. Tightening from a different hole releases the binding so it’s actually tight and not just bound up. This also applies to Jacobs chucks.

I was taught to tighten on every hole, ending on the same one I started on. This gives a tighter grip with less torque on the wrench. No need to really crank it when doing this.

the chuck also makes a difference in how hard to crank. I have a Nova g3 and several no name chucks. The no name chucks definitely need more torque to hold the same as the Nova. I believe it’s due to sloppy machining.
 
Kent Reisdorph said:
I have observed turners doing a couple of things with chucks that make me wonder.

1. I see turners tightening the chuck with all their might. That doesn't seem necessary and can actually make the tenon weaker.
2. After they tighten the chuck with all their might, they rotate 180 degrees it and tighten the opposite pinion. Why? Habit?

Curious what you all think.
Click to expand...

Agree on the first part. For the second, I do it out of habit. I know I'm turning the same scroll gear, but it just feels right. If I had to come up with a rationale, at least for chucks with internal pinions, I'd say it's possible that one of the pinion assemblies sticks or drags more than the other — at least under the downward pressure of the chuck key — and so tightening both is a couple seconds of work that does no harm and could possibly help in a rare, contrived scenario. :)
 
Kent Reisdorph said:
2. After they tighten the chuck with all their might, they rotate 180 degrees it and tighten the opposite pinion. Why? Habit?
Click to expand...
One reason - turning the chuck allows you to inspect the tenon that it's seated properly all around. Tightening from the other hole is just an "excuse" to remember to look.
But the other reason (that also apples to Jacobs chucks and others) is to take up any gear lash in the chuck - probably not so necessary on a good quality chuck gripping wood, but it is a long-observed habit with some of us.
 
I probably go too tight sometimes, but I try to just do firm snug and keep checking as I work. Using the opposite side seems pointless to me.

As a new turner, I thought my big 5" Nova Titan gave me a larger clamping range. I have since made some wood guides for sizing the tenons and mortises to the optimal diameters of my different jaw sizes. Work is way more secure when sized correctly. Pieces also spin more true when you're not crushing fibers unevenly with the cornerrs of your jaws.
 
Mike Novak said:
was taught to tighten on every hole, ending on the same one I started on.
Click to expand...

Me too in high school shop.

Also reinforced by John Brewer a long time a member of the Chesapeake woodturners. John told me on several occasions and in club demos that he learned to tighten every hole from his freind Mr Black one half of the Black and Decker.
 
hockenbery said:
Me too in high school shop.

Also reinforced by John Brewer a long time a member of the Chesapeake woodturners. John told me on several occasions and in club demos that he learned to tighten every hole from his freind Mr Black one half of the Black and Decker.
Click to expand...

Mr. Decker told me I didn't need to do that. ;)

It seems like most folks do it because, "That's how I've always done it." Nothing wrong with that.
 
Axminster also has three tightening slots. I use all three as there alway seem to tighten just a little more ( I don’t think I over tighten, but do tighten it. I tighten all three not from habit but it does release any binding of the ring gear. And as Dave said I look to make sure the part is well seated in the jaws.
 
I tighten the grip from the chuck to precisely to the pressure I have pre-set with the screw function (slip clutch) on my battery drill.
I only use one of the key holes in the chuck to get that precise pre-set pressure.
I place the jaws so that each set is equal distance from the end and side grain and that way they all jaws have a very similar resistance to the fibre crushing.

Besides being able to precisely set how tightly I want the the drill to clamp/expand, the other reason I use a drill for opening and closing the jaws on my chucks is that it is way way faster than doing it by hand with a T-bar. There are times when I repeatedly open and close the jaws on a chuck completely one way then the other, like when I'm re-turning pre-turned blanks, and the the speed of the drill makes a big difference.

Here is a video of doing it the slow way first - 40 seconds
and then the fast way 6 seconds
If you see a Subscribe button on the following video, ignore it!
I don't seem to able to stop that happening sometimes
View: https://www.youtube.com/embed/-bzTOafyZcw

​
 
Last edited:
The chuck scroll that moves the chuck jaws has some internal clearance. There are woodworking chucks that I have disassembled for cleaning and lubrication that are fairly sloppy with regard to scroll clearance. in fact, some scrolls are not machined. Where the scroll shifts during tightening affects the center of rotation of the workpiece and the pressure of each jaw on the workpiece. With wood, does this really matter? If the chuck exhibits sloppy clearances, it would be beneficial to tighten each pinion or if the pinion is on the chuck key, tighten from each hole in the chuck body.

I tighten each pinion or from each hole in the chuck body, mainly from a metalworking background prospective.

On a metal lathe (metal lathe chucks have much tighter clearances) it does matter. It can be easily demonstrated with a dial indicator that all pinions should be tightened especially if you want concentric accuracy to a previously machined surface.
 
Kent Reisdorph said:
That chuck has about twice the travel as the SuperNova 2.
Click to expand...

Darryl Fective said:
I think they should've named it the Nova Tighten. :D
Click to expand...

I'll pay that one Darryl...😁

And, yes Kent, the Nova Titans do have a lot of travel. I'm not sure how much in relation to my SN2s, but the hex key in the drill sure takes away any waiting time to get a quick grip on things!
 
I use Vicmarc chucks that take a standard hex key to lock the jaws. I've seen people use a standard bent alken key to tighten the jaws.
 
Interesting discussion. I would add that given the cost, and that anyone--experienced and inexperienced alike--can purchase one, it would not be an unreasonable request for the manufacturers to weigh in on this. Afterall, one would assume that manufacturers test their products before putting them out in the market. How much torque do they apply? The question: just how much torque will of course depend somewhat on the wood, but also on the inner workings of each device. They may look like a machinist's chuck, but the chuck for wood is different-- and the number of different jaws available attest to that. I am curious what the manufacturers might have to say about tightening, given the number of previous comments and techniques above.
 
J. Paul Fennell said:
Interesting discussion. I would add that given the cost, and that anyone--experienced and inexperienced alike--can purchase one, it would not be an unreasonable request for the manufacturers to weigh in on this. Afterall, one would assume that manufacturers test their products before putting them out in the market. How much torque do they apply? The question: just how much torque will of course depend somewhat on the wood, but also on the inner workings of each device. They may look like a machinist's chuck, but the chuck for wood is different-- and the number of different jaws available attest to that. I am curious what the manufacturers might have to say about tightening, given the number of previous comments and techniques above.
Click to expand...
The info you will get from mfrs for tightening torque is in the manuals for the chucks, and it is not very detailed. I suspect a primary reason in the USA is liability, and second the variation in the wood. Below is an excerpt from a Nova manual. From experience I know their recommended guidelines for jaw size/work dia, work length, and rpm are very, very conservative, but….they are a good place for the beginner to start.

Nova
As with other work holding methods, an extremely cautious and sensible approach is necessary. With the LITE G3 Chuck it is not possible to give exact directions as to the amount of tightening pressure required for adequate work holding or approved chisel cutting techniques. Follow closely strict guidelines in this manual for different jaw types on wood blank diameters and length, plus strictly follow recommended lathe speeds.
 
Reading through the comments I likely get my jaws tighter than most, at least with rough work. I typically use tenons. I can get pretty aggressive when roughing with a 5/8” shaft bg, and have “removed” quite a few “snug” pieces from the jaws while cutting. I don’t have them come out when I crank ‘em down.

When doing lighter finishing cuts of course the cutting load is much less and the grip torque can be less. The tenon length can be less
As well. Just depends on the load applied. Unbalanced work places more load on work attachment and is to be addressed accordingly.
 
For the most part, I tighten down firmly, which may be more than “necessary”. I often use Oneway profile jaws when turning green wood and want to ensure the teeth get a good bite, especially when roughing bowls with an oversized tenon (so that I have enough to true a dovetail tenon once dry). I find that when I am using dovetail jaws I still tighten firmly, maybe just out of habit. I do not see an issue with a properly sized tenon. “Over tightening” dovetail jaws on on over sized tenon can create problems (I think), as the corners of each jaw would bite harder and possible lead to failure, particularly in a side grain blank (where the grain is running parallel to the face of the jaws). I guess it’s worth mentioning that my tenons are always turned away and never used as the finished foot. I also tighten a chuck from each position. A habit likely developed when I worked on aircraft and learned to do this with a Jacob’s chuck to ensure concentricity. It also serves as the first step to ensure that I have released the spindle lock before starting the lathe. As with most things in woodturing, this is what works for me, YMMV.
 
I know some turners only tighten in one hole. Years and years ago I heard that machine shop workers all tighten in every hole, and go around a time or two. That has been my standard method for most of at least the last 20 years. I will go around twice. I get it snug, go to the next hole and get it snug again, and then repeat.

robo hippy
 
Some may do it without knowing why, but the point is pushing the internal clearance around the chuck. It’s a real thing. And it’s important to move around the proper direction too…for a typical Jacob’s chuck on a drill press, you move to the next hole on the right side.

Tim
 
Kent Reisdorph said:
I have observed turners doing a couple of things with chucks that make me wonder.

1. I see turners tightening the chuck with all their might. That doesn't seem necessary and can actually make the tenon weaker.
2. After they tighten the chuck with all their might, they rotate 180 degrees it and tighten the opposite pinion. Why? Habit?

Curious what you all think.
Click to expand...
I tighten each jaw on my SN2. I believe the critical task is to spend the time to make a proper tenon. If it's sloppy, redo it, don't take a chance. After tightening the jaws, check again after a few minutes of turning & retighten. More critical if using green wood.
Most often when I had tenon failures, it's result of either sloppy tenon or improper tenon diameter.
 
Kent Reisdorph said:
I have observed turners doing a couple of things with chucks that make me wonder.

1. I see turners tightening the chuck with all their might. That doesn't seem necessary and can actually make the tenon weaker.
2. After they tighten the chuck with all their might, they rotate 180 degrees it and tighten the opposite pinion. Why? Habit?

Curious what you all think.
Click to expand...
Agree with you on #1. Snug is good enough because of the huge mechanical advantage.
On #2, definitely tighten both sides for the same reason that you tighten all three positions on a drill chuck (there is a lot of friction between the ring gear and the chuck body plus the friction between the scroll and teeth on the bottom of the base jaws).

If you've ever disassembled a scroll chuck (or Jacobs chuck) you can appreciate the amount of slop and breakout friction tells you that it makes sense to tighten from all the locations.
 
Bob Raasch said:
I tighten each jaw on my SN2. I believe the critical task is to spend the time to make a proper tenon. If it's sloppy, redo it, don't take a chance. After tightening the jaws, check again after a few minutes of turning & retighten. More critical if using green wood.
Most often when I had tenon failures, it's result of either sloppy tenon or improper tenon diameter.
Click to expand...
Right. I use a detailed spindle gouge on the tenon to get a good bevel and a nice flat spot at the base.
 
Mike Novak said:
all chucks have a little bit of play in the tightening ring. Because of this, the ring can bind up, making it seem tighter than it is. Tightening from a different hole releases the binding so it’s actually tight and not just bound up. This also applies to Jacobs chucks.

I was taught to tighten on every hole, ending on the same one I started on. This gives a tighter grip with less torque on the wrench. No need to really crank it when doing this.
Click to expand...

^^^^^ This is a good explanation by Mike Novak. (I was taught this very same principle by an old machinist on my very first job after graduating from high school.)

My Oneway Stronghold chucks have only two keyholes, and my Jacobs chucks have three. For the Stronghold chucks, I gradually increase the pressure while alternating between the keyholes several times.

For Jacobs style chucks I use the same strategy but tighten each keyhole only once. For the reasons outlined above, using only a single keyhole, it's sometimes possible to not have the drill bit not exactly centered. I have proven this to myself by analyzing the different methods of tightening the chuck.

As for the OP, I'd say tightening with all my might is excessive, but it does need to be a very firm grip.

-o-
 
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