Truing work in the 4 jaw chuck

[140mower]

I was putting a pulley into the 4 jaw so I can bore out it's already oversized bore and make it fit my motor. The pulley has a 1" bore and the motor has a 7/8" shaft. Going to have to run the lathe in reverse pretty quickly to put that much back into the bore.....
I thought as we have quite a few new members I would start a thread on truing up parts in the 4 jaw, and hopefully we can find a few different odd ball setups to post up pictures of that will show how useful the 4 jaw is.
I'll start with how I pick up a bore or center punch mark (using a smaller center of course) and dial it in.

This is a good method for centering the bore, when the outside is out of round for whatever reason.

 

[curmudgeon]

Very timely for me. Thank you!

I spent a few hours practicing yesterday; centreing as best I could with all available patience, turning, re-chucking the other end and repeating until my toes froze. My touch at easing off the 4 jaw chucks is getting better, but I never got all 4 lined up so that I could not see and feel the transition. I will continue to use the 4 jaw even when the 3 jaw would suffice until I'm consistently good with it.

On the success side:
- I didn't spill any blood or break any thing
- I can now use the half-nut to engage/disengage longitudinal feed without keeping my left hand hovering over the e-stop
- I got to try out a boring bar

I haven't worked out tomorrow's lesson plan yet. So many basic things to learn and practice, practice, practice.

 

[140mower]

Very timely for me. Thank you!

I spent a few hours practicing yesterday; centreing as best I could with all available patience, turning, re-chucking the other end and repeating until my toes froze. My touch at easing off the 4 jaw chucks is getting better, but I never got all 4 lined up so that I could not see and feel the transition. I will continue to use the 4 jaw even when the 3 jaw would suffice until I'm consistently good with it.

On the success side:
- I didn't spill any blood or break any thing
- I can now use the half-nut to engage/disengage longitudinal feed without keeping my left hand hovering over the e-stop
- I got to try out a boring bar

I haven't worked out tomorrow's lesson plan yet. So many basic things to learn and practice, practice, practice.

Yes, practice...... I am still well in the realm of learning to be comfortable using the 4 jaw. One thing I have learned is to work one pair of jaws at a time, 1&3 or 2&4 and work them to zero on the indicator, then, from wherever the other pair are, you bring them to zero. As hard as it is for me (kind of a sporadic thinker), a slow and methodical approach is the fastest.

 

[Tecnico]

I was putting a pulley into the 4 jaw so I can bore out it's already oversized bore and make it fit my motor. The pulley has a 1" bore and the motor has a 7/8" shaft. Going to have to run the lathe in reverse pretty quickly to put that much back into the bore.....
I thought as we have quite a few new members I would start a thread on truing up parts in the 4 jaw, and hopefully we can find a few different odd ball setups to post up pictures of that will show how useful the 4 jaw is.
I'll start with how I pick up a bore or center punch mark (using a smaller center of course) and dial it in.

This is a good method for centering the bore, when the outside is out of round for whatever reason.

Good Topic!

I've gotten some volume of experience recently with a couple of projects and I'm looking forward to a bit of discussion now on how to do it right - tricks of the trade!

Great start with using the center to pick up on the bore, too obvious to be obvious!

I have a 4 jaw on my dividing head so it's always going to be part of the setup.

D

 

[trevj]

Use the dial indicator horizontal, and located behind the work, or the rod you are indicating off.

Adjust the cross slide, so that the needle, is moving the same way as the part when it is turned, ie: when the needle is moving away from the operator, is when the part high point is moving away from the operator.

Now, you have easy access to the adjuster key hole at the front of the lathe. Pick a direction, set the needle to max throw (hand turning the chuck) that can be got with a set of jaws horizontal, and tweak the nearest jaw in or out, as you see fit. You can watch the needle, as you are tweaking the part into alignment. Don't worry so much about working both sides, at the same time, esp when the part simply cannot fall off the lathe, as shown above (held in place by tailstock pressure). Simply hand turn the chuck to bring the opposite jaw to you.

This was a game changer for me, and I taught it to all that would listen and see.

This works well when you are indicating off a bore, at a weird angle too, as you do not really care how FAR the indicator travels, just that you can adjust it until the needle does not move.

 

[Tecnico]

Yes, practice...... I am still well in the realm of learning to be comfortable using the 4 jaw. One thing I have learned is to work one pair of jaws at a time, 1&3 or 2&4 and work them to zero on the indicator, then, from wherever the other pair are, you bring them to zero. As hard as it is for me (kind of a sporadic thinker), a slow and methodical approach is the fastest.

I could have written what you said!

D

 

[Proxule]

Going to have to run the lathe in reverse pretty quickly to put that much back into the bore.....

LOL

 

[140mower]

In this setup, I am cleaning up the drilled hole with a boring bar, ahead of running a reamer through for a close running fit. It started out as a cener punch prick that I dialed in with a dead center as above.

 

[140mower]

I could have written what you said!

D

I beat ya....

 

[Susquatch]

I can now use the half-nut to engage/disengage longitudinal feed without keeping my left hand hovering over the e-stop

I'm not sure about this.... All the lathes I've used don't use the half nut to engage feed. It's used to engage threading. Not saying you are not right, just saying it's not how mine works or any others I've used.

Does your lathe have a crossfeed? I could see where lathes that don't have a crossfeed might use the half-nut for everything.

Generally speaking, there is a gear set inside the saddle that gets engaged as either longitudinal or crossways feed. Because of the gear set, it runs at a different speed than the pitch of the leade screw. However, when threading, the half nut is engaged which follows the leade screw at 1:1.

There should be two charts on your lathe - one for thread pitch and one for feed rate.

Perhaps on lathes without a cross feed there is only one chart.

I suppose, there isn't any harm in using the half nut to engage feed, but the charts would be wrong in that case. It would prolly also be hard on the half nut to be used for both. Might be other reasons too. I dunno.

Anyway, something to look at.

 

[Susquatch]

One thing I have learned is to work one pair of jaws at a time, 1&3 or 2&4 and work them to zero on the indicator

I have always found it better and faster to work to the halfway point on the indicator, not to zero. Ie Rotate to find full runout, then loosen and tighten to take half of that out. But maybe you mean work the indicator toward zero movement.

Also, while I do what you do with the indicator setup on top of the work, I've seen many machinists set the indicator up on the back of the lathe and adjust from the front. For some reason they find this easier to do. Perhaps it's because you can get at both jaws without having to rotate the chuck.

Lastly, sometimes the high point just doesn't want to ever line up with a jaw. In this case, I find it better to adjust two jaws at once (at 45 degrees to the high spot).

Maybe when everyone who is interested in this is happy, we can do an axial concentricity alignment too. I have made some custom chucks to do that with and I'd bet some would find it interesting. But first things first!

 

[curmudgeon]

Adjust the cross slide, so that the needle, is moving the same way as the part when it is turned, ie: when the needle is moving away from the operator, is when the part high point is moving away from the operator.

Brilliant! - I have some unlearning to do on this point, but way more intuitive than my "crank the jaw down to reduce the dial indicator reading" mantra. I have a long way to go to develop some level of muscle memory for loosening a jaw on one side so that I can creep up on the setting by tightening the other side. Many, many, many over-shots but practice helps.

 

[Susquatch]

Brilliant! - I have some unlearning to do on this point, but way more intuitive than my "crank the jaw down to reduce the dial indicator reading" mantra. I have a long way to go to develop some level of muscle memory for loosening a jaw on one side so that I can creep up on the setting by tightening the other side. Many, many, many over-shots but practice helps.

Another little tip here.

At first, the part will be miles away from center. You can simply loosen the far end off a lot, then push the close end to where you want it, and then tighten the back end back up. As you tighten it, some of what you wanted will get taken away. That's when you push a bit more. If you work toward the half way in the indicator you can get there a lot faster than worrying about developing "the touch". Of course, that touch is still important as it gets down to the wire, but it is still much faster and also much more intuitive.

 

[140mower]

I have always found it better and faster to work to the halfway point on the indicator, not to zero. Ie Rotate to find full runout, then loosen and tighten to take half of that out. But maybe you mean work the indicator toward zero movement.

Also, while I do what you do with the indicator setup on top of the work, I've seen many machinists set the indicator up on the back of the lathe and adjust from the front. For some reason they find this easier to do. Perhaps it's because you can get at both jaws without having to rotate the chuck.

Lastly, sometimes the high point just doesn't want to ever line up with a jaw. In this case, I find it better to adjust two jaws at once (at 45 degrees to the high spot).

Maybe when everyone who is interested in this is happy, we can do an axial concentricity alignment too. I have made some custom chucks to do that with and I'd bet some would find it interesting. But first things first!

To get the first pair, yes, I just move to zero movement, then, I zero the indicator and bring the other two jaws in to the zero. I only use zero because it makes the math easier for me.
And I agree, putting the indicator behind the part is in some ways easier, but then I would have had to clean up back there before the picture. Also, when it's on the top, I can bring the cross slide in or out until the indicator is exactly centered by watching the dial.
And, figured if I opened up Pandora's box just a wee bit, I might learn some better habits.....

 

[Susquatch]

And I agree, putting the indicator behind the part is in some ways easier, but then I would have had to clean up back there before the picture.....

And, figured if I opened up Pandora's box just a wee bit, I might learn some better habits..

I really do wish we lived closer. You are hilarious.

As I added that bit about just opening the other jaw and pushing with the one side, I realized that the lack of "the touch" is the reason many guys do it front and back. The part won't fall if it's pushed back N forth instead of up and down, and you can do both without rotating the chuck!

I'm not changing my habits though...... LOL

 

[YYCHM]

Centering Work in a 4-Jaw Chuck

I've always struggled with centering work in a 4J. Some times it would take me over an hour in order to get something even remotely close. These instructions work, and work great. https://littlemachineshop.com/images/gallery/PDF/centering4-jawchuck.pdf Now if I could only find something...

canadianhobbymetalworkers.com

 

[140mower]

I'm not changing my habits though...... LOL

Come on now...... "We're men, we can change if we have to."...... Red Green

 

[curmudgeon]

I'm not sure about this.... All the lathes I've used don't use the half nut to engage feed. It's used to engage threading. Not saying you are not right, just saying it's not how mine works or any others I've used.

Does your lathe have a crossfeed? I could see where lathes that don't have a crossfeed might use the half-nut for everything.

Generally speaking, there is a gear set inside the saddle that gets engaged as either longitudinal or crossways feed. Because of the gear set, it runs at a different speed than the pitch of the leade screw. However, when threading, the half nut is engaged which follows the leade screw at 1:1.

There should be two charts on your lathe - one for thread pitch and one for feed rate.

Perhaps on lathes without a cross feed there is only one chart.

I suppose, there isn't any harm in using the half nut to engage feed, but the charts would be wrong in that case. It would prolly also be hard on the half nut to be used for both. Might be other reasons too. I dunno.

Anyway, something to look at.

OK, so I really want to ensure I'm doing this correctly, so please everyone that sees me doing, or even appearing to do something stupid, please call me out and save me from my ignorance and obstinance; very much appreciated!

I just re-read the manual for my 10x22 Grizzly G0602 and I think I'm on the correct track, but I (and/or Grizzly) might be wrong...

My lathe does not have power cross-feed. The half-nut is used to engage the leade screw for powered longitudinal feeding and for threading. There is a feed chart with inches/rotation, and both metric (mm TP) and SAE (TPI) thread charts.

After this latest re-read of the manual, I see that it does not explicitly say that I can engage the half-nut while the spindle is turning. It would be a nuisance to have to turn the lathe off every time I wanted to engage the half-nut. The leade screw is turning much faster for threading and in that situation isn't the half-nut engaged with the lathe on while waiting for a magic number to show up on the thread dial indicator?

Is it bad to engage the half-nut for powered longitudinal feeding while the lathe is running?

 

[Susquatch]

I kinda figured that's what we would find - no power cross feed so they used the half nut for both.

Yes, the half nut is designed to be used while the screw is turning. Basically you lightly engage it until it slips into engagement when the tooth alignment arrives. It should never be forced or jammed. Just light as she goes till she is happy and it drops into place

 

[trevj]

I have always found it better and faster to work to the halfway point on the indicator, not to zero. Ie Rotate to find full runout, then loosen and tighten to take half of that out. But maybe you mean work the indicator toward zero movement.

Also, while I do what you do with the indicator setup on top of the work, I've seen many machinists set the indicator up on the back of the lathe and adjust from the front. For some reason they find this easier to do. Perhaps it's because you can get at both jaws without having to rotate the chuck.

Lastly, sometimes the high point just doesn't want to ever line up with a jaw. In this case, I find it better to adjust two jaws at once (at 45 degrees to the high spot).

Maybe when everyone who is interested in this is happy, we can do an axial concentricity alignment too. I have made some custom chucks to do that with and I'd bet some would find it interesting. But first things first!

Dunno about others, I do it solely because it puts where I am adjusting, directly in line with where the indicator reads, and it's dead easy to reach the jaw adjuster, instead of losing my mind, trying to rotate the chuck to the high point, then reaching around the indicator trying to manipulate the adjuster, The direction I need the indicator tip to move, intuitively becomes the direction I need to adjust the jaw.