Bowl Turning Chuck Problem

[vtgaryw]

Wasn't sure if I should post this here or under "Other Things we Make" but it's more of a tool question.

I have the Penn State Utility Grip Chuck. It's been fine for what I've used it for up to now (pen drilling jaws, misc small OD turnings.) Recently, when casting some mini pin cones in resin, I cast a blank for a small bowl. It has a tenon about 3/8" long (so long than the instructions for the chuck said I need.)

The outside turned beautifully, but when I try turning the inside, the chuck opens up. Can't see what I'm missing here. Any ideas?

Thanks,

Gary

 

[monophoto]

When you say 'the chuck opens up', I presume you mean that the jaws become loose as you turn.


I have the same chuck, and I have noticed that the jaws sometimes loosen gradually over time. Based on what I have read and seen on various YouTube videos and in demonstrations, it's not uncommon for chucks to loosen over time, and I can easily understand how vibration could cause that to happen. And if you are a bit aggressive when hollowing a bowl, you can easily create a lot of vibration and stress on the chuck. Everything I have seen and read says that good turning practice is to stop periodically and check that the chuck is still tight.

 

[Gary Beasley]

Looks like from the picture it has straight sided jaws with no knurls or ribs to grip with. That and tommy bars are not the greatest for applying pressure to the jaws. If you are intent on doing bowls in the future do some research on quality chucks. I have nova chucks with dovetail jaws and like them. Record Power is another brand with an excellent reputation.

 

[BeeAMaker]

I too have the same chuck - same issues. I try to do a mortise instead of a tenon. With a mortise you are tightening the jaws with the spin, so it can only tighten against the piece as they tend to fly outword. Also you can try some thick rubber bands wrapped around the jaws to help keep them from loosening. Ultimately I purchased a Nove G3 chuck with dove tails.

 

[Dieseldoc]

Wasn't sure if I should post this here or under "Other Things we Make" but it's more of a tool question.

I have the Penn State Utility Grip Chuck. It's been fine for what I've used it for up to now (pen drilling jaws, misc small OD turnings.) Recently, when casting some mini pin cones in resin, I cast a blank for a small bowl. It has a tenon about 3/8" long (so long than the instructions for the chuck said I need.)

The outside turned beautifully, but when I try turning the inside, the chuck opens up. Can't see what I'm missing here. Any ideas?

Thanks,

Gary

Gary:

For this problem with out spending money on new tool I would suggest using a Jam chuck. For information on jam chuck just go to You tube and you find several videos on how to.

If you do a lot of bowl turning you might also want to check out using a cole chuck.

Charlie

 

[JimB]

The problem might be the resin being very hard. I believe those jaws have 'teeth' on the inside that bite into the wood giving the grip. If the resin is hard perhaps the teeth aren't biting into the material. The resin is also probably a bit slippery compared to wood so compounding the problem. So it may be a gripping problem not an issue with the jaws coming loose.

In any case, when ever using a chuck, you should tighten the jaws periodically as you turn. With a wood tenon the chuck will compress the wood and you will find just after a few minutes you can tighten the jaws a little bit more.

 

[JimB]

Wasn't sure if I should post this here or under "Other Things we Make" but it's more of a tool question.

I have the Penn State Utility Grip Chuck. It's been fine for what I've used it for up to now (pen drilling jaws, misc small OD turnings.) Recently, when casting some mini pin cones in resin, I cast a blank for a small bowl. It has a tenon about 3/8" long (so long than the instructions for the chuck said I need.)

The outside turned beautifully, but when I try turning the inside, the chuck opens up. Can't see what I'm missing here. Any ideas?

Thanks,

Gary[/QUOTE

Gary:

For this problem with out spending money on new tool I would suggest using a Jam chuck. For information on jam chuck just go to You tube and you find several videos on how to.

If you do a lot of bowl turning you might also want to check out using a cole chuck.

Charlie

What you are describing is for cleaning up the bottom of a bowl. I believe the OP is having a problem holding the tenon to hollow the inside of the bowl.

 

[leehljp]

. . . Also you can try some thick rubber bands wrapped around the jaws to help keep them from loosening. Ultimately I purchased a Nove G3 chuck with dove tails.

This is what I do, and I have a large supply of different sized O-rings. I often put an O ring on and tighten against the O ring instead of the jaws. Holds better and grips better. Someone told me to do that when I was beginning and I have not had a problem. I use rubber bands and O rings without even thinking when possible.

I recently ordered some of these rubber bands for a different reason, but there are all sizes of rubber bands available.
https://www.amazon.com/gp/product/B003SBXPPU/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

I am adding in here: A couple of times, I have used short but wide rubber bands around each individual jaw; this works when the jaw is clamping a tenon or when gripping the inside of the bowl.

 

[chartle]

I have the same set and I usually use a mortise but right off the bat it looks like your tenon is too big.

When clamped down the jaws should almost be touching. Right now you are only grabbing the bowl in 8 very small areas.

Same for the mortise. The jaws should just barley fit in the recess and expand only a little before tight.

But as posted above it maybe that the jaws are not getting a good grip on the hard resin.

 

[vtgaryw]

I have the same set and I usually use a mortise but right off the bat it looks like your tenon is too big.

When clamped down the jaws should almost be touching. Right now you are only grabbing the bowl in 8 very small areas.

Same for the mortise. The jaws should just barley fit in the recess and expand only a little before tight.

But as posted above it maybe that the jaws are not getting a good grip on the hard resin.

Thanks for all the responses. Just to clarify, I cored the resin with a approx 2" diameter piece of hardwood, so the tenon is maple. I like the explanation that the tenon diameter is too big. I didn't realize I needed to get it even smaller than I made it.

Also: it's opening up right away. Pretty much within 20-30 seconds of putting a tool to the inside of the bowl. And it's not the jaws coming loose from the carrier, it's the carrier loosening up on the part attached to the spindle. Oh, and the jaws *are* serrated on the inside.

I know if I ever got into bowl turning I'd need a better chuck, but I figured it should be good for a simple 4" diameter resin bowl.

By the way, the outside came out beautiful. I'm hoping not to screw it up now. Not sure if I can figure out how to turn the OD of the tenon down at this point in time.

Gary

 

[raar25]

Chances are the chuck jaws are digging in a little from vibration and causing the resin to give. This in turn caused more vibration and the jaws actually loosen up. If you listen carefully you will probably be able to hear the difference in the noise as the chuck starts to loosen. I don't use the jaws with teeth anymore because they don't hold as well as the dovetail jaws do since the dovetail jaws increase their holding pressure as they bite into the material but as mentioned above these jaws are only biting on no more than 8 spots. Also these jaws are pretty thin and will flex more than some of the Nova jaws will which is what starts the loosening process.

So bottom line is just tighten often. I also like Hanks solution which seems like it will reduce vibration and will have to give that a try.

 

[chartle]

Also: it's opening up right away. Pretty much within 20-30 seconds of putting a tool to the inside of the bowl. And it's not the jaws coming loose from the carrier, it's the carrier loosening up on the part attached to the spindle. Oh, and the jaws *are* serrated on the inside.

I'm not understanding this. This makes it sound like the entire chuck is somehow spinning off the headstock threads.

I understand what you mean by the jaws but not the carrier or the spindle.

The chuck has interchangeable jaws and the entire chuck spins onto the headstock threads and when the chuck spins it should tighten onto the headstock threads.

 

[BeeAMaker]

Also: it's opening up right away. Pretty much within 20-30 seconds of putting a tool to the inside of the bowl. And it's not the jaws coming loose from the carrier, it's the carrier loosening up on the part attached to the spindle. Oh, and the jaws *are* serrated on the inside.

I'm not understanding this. This makes it sound like the entire chuck is somehow spinning off the headstock threads.

This happens to this chuck quit often when the lathe is turned off from a high speed. The inertia spins the chuck right off the threads. However this shouldn't happen while turning. If it does then the head stock is spinning in the wrong direction.
:glasses-cool:

 

[Charlie_W]

Also: it's opening up right away. Pretty much within 20-30 seconds of putting a tool to the inside of the bowl. And it's not the jaws coming loose from the carrier, it's the carrier loosening up on the part attached to the spindle. Oh, and the jaws *are* serrated on the inside.

I'm not understanding this. This makes it sound like the entire chuck is somehow spinning off the headstock threads.

This happens to this chuck quit often when the lathe is turned off from a high speed. The inertia spins the chuck right off the threads. However this shouldn't happen while turning. If it does then the head stock is spinning in the wrong direction.
:glasses-cool:

Okay.....does your chuck have an insert which you can change for different size spindles? If so, sounds like it is a threaded insert. Many chucks have the option for a grub screw (set screw) which will lock the insert to the chuck. Apparently the deceleration when powering off is causing either the chuck or the insert to unscrew.
You say it occurs during turning.....does the chuck or insert screw on the spindle up tight against the shoulder/face of the spindle? If not, a washer may help take up this space and allow the chuck to seat squarely and firmly against the spindle face.
You may need to lock the chuck to the spindle with a grub screw if your spindle has a channel for the screw to come against.... otherwise, the screw will bugger up the spindle threads.

A important safety factor is to turn the speed down low before turning off the lathe.
Should someone/you turn the lathe on with it at a high speed, an out of balance piece could come off causing injuries or worse.

 

[monophoto]

The trajectory of this post has really evolved! I thought I understood that the problem was that the jaws were loosening on the tenon, but the conversation now seems to be suggesting that the problem is that the entire chuck is unscrewing from the lathe spindle.

The question related to the PSI Utility Chuck - this is a basic tommy-bar chuck that has a native 1"x8pti thread, but that is supplied with a 3/4"x16tpi adapter for use with minilathes. The photograph in the original post shows the No 2 jaws that come with the chuck (basic 50mm jaws that are neither flat or dovetail - instead, there is a ridge at the edge of the jaw that grips the tenon). It does not have a grub screw to lock the adapter into the chuck body, or to lock the chuck to the lathe spindle.

I think we need a better explanation of the problem from the original poster. Is the problem that the jaws are losing their grip on the tenon, or is it that the chuck is unscrewing from the lathe spindle? And I would add another question - is this a new chuck or has he been using it for some time? And if it is 'experienced', is the problem he is reporting something that first materialized when he used it to turn a bowl from a composite wood-plastic blank?

As Charlie and Glenn have correctly said, IF the problem is that the chuck is unscrewing from the lathe, then it is almost certain that the OP running the lathe in reverse - the normal rotation of a lathe tightens the chuck to the lathe spindle.

However, it the problem is that the jaws are actually losing their grip on the tenon, then I still suspect that vibration is causing the jaws to loosen.

I've been successfully using the same chuck for about seven years; I've noticed that the jaws sometimes loosen when used in expansion mode (with a mortise mount), but I don't recall having the jaws lose their grip in compression mode (with a tenon). I am acutely aware that the chuck can unscrew itself from the lathe spindle if I stop the lathe without first reducing the speed - I've had to jump out of the way a couple of times when it came off the lathe entirely avoid having it land on my foot!

The other possibility is that if this is a new chuck, it is possible that it is defective.

 

[chartle]

Also: it's opening up right away. Pretty much within 20-30 seconds of putting a tool to the inside of the bowl. And it's not the jaws coming loose from the carrier, it's the carrier loosening up on the part attached to the spindle.

The trajectory of this post has really evolved! I thought I understood that the problem was that the jaws were loosening on the tenon, but the conversation now seems to be suggesting that the problem is that the entire chuck is unscrewing from the lathe spindle.


I think we need a better explanation of the problem from the original poster. Is the problem that the jaws are losing their grip on the tenon, or is it that the chuck is unscrewing from the lathe spindle?

Somehow I think what I highlighted in red seems important.

 

[chartle]

to continue Gary are you spinning the lathe backwards to make turning the inside of the bowl a little easier?

 

[monophoto]

to continue Gary are you spinning the lathe backwards to make turning the inside of the bowl a little easier?

Another factoid for the mix: Not all lathes can be spun backwards. The photo he posted with the original question shows only that the headstock of his lathe is painted white. But I found a posting from about three years ago when he mentioned that Gary had just acquired a Rikon 70-220VSR (which has a white headstock) and that is advertised as having a reverse capability.