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Concentricity of Lathe Chuck to Drive Center???

RFGuy

First, a shout out to masonsailor2 for inspiring me to attempt a salt and pepper mill (https://forum.shopsmith.com/viewtopic.php?p=258147#p258147) for the first time. I am still new at woodturning, so these salt & pepper mills (see below) are far from perfect, but I was attempting to copy the design of a salt & pepper mill set that I bought previously. So, here is my question. For woodturning, should I expect concentricity between a drive hub and a chuck? I followed a video online for how to turn salt & pepper mills. I started with a single blank between my Shopsmith drive hub and a live center in the tailstock. I rounded this blank, then cut tenons on each end for chucking the blank. Next, the blank is drilled for the salt/pepper cavity inside. Then I cut the tenon in the salt/pepper mill top, then parted the top from the bottom of the blank. From this point on, you are supposed to switch to using a lathe chuck to drive the blank which is what I did. This is where I encountered the problem. I had to re-turn the blank for roundness when switching from the drive hub to the lathe chuck. Why is this? I would have expected the center of the drive hub to match the center of the lathe chuck, but this was far from the case. I should point out that I did align the drive hub to the tailstock live center and confirmed this multiple times. Also, I am using the Nova G3 chuck with the Shopsmith arbor adapter and the chuck is assembled correctly, i.e. the numbered jaws match the chuck numbering.

I know there are different techniques to go about a particular task in woodturning like this one. Just wondering what I did wrong, or whether this is a common thing known in woodturning, i.e. that you can't go from a drive hub to a chuck turning without having to start over due to the lack of concentricity.

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BuckeyeDennis

It sounds to me as if your chuck could have excessive runout. If you have a magnetic-base indicator, you can easily check the runout of the jaws (turning the spindle by hand). If not, you could use the tool rest as a crude indicator, just by placing one end of it close to the jaws, and watching the air gap. If you find runout, then test inward from there. Jaws, chuck body, chuck adapter, spindle.

If you don't find runout, it may be that your workpiece was chucked up at a skew angle to the spindle & chuck. Check to make sure that the ends of the jaws are coplanar -- I usually seat them against the flat of the workpiece while tightening the chuck. For long workpieces, it can be helpful to support the far end with the tailstock while tightening the chuck.

RFGuy

Dennis,

Thanks. I appreciate your advice here. Yeah, I thought about trying to check runout, but I wasn't quite sure how to do it with the lathe chuck. So, you are suggesting trying to measure the runout directly from the chuck jaws, is that correct? I wasn't sure if I should try to turn a blank and measure runout from it or to do it directly on the chuck jaws. For comparison though, how do I measure runout on the drive hub? Seems like it would be difficult to do since the center of the drive hub is a small tapered point. Unfortunately, I don't have a magnetic base dial indicator. Only one that I have is one for mounting in miter slots for checking saw alignment and is not magnetic (might be difficult to mount for this purpose). I was looking at the one Nick Engler recommended before, e.g. in the planer knife setup video, but then I found bad reviews online for it so didn't buy it. Can't remember the brand he used. Can anyone recommend a good quality magnetic base dial indicator to me?

BuckeyeDennis

You have to measure jaw runout on the jaws themselves -- although you might want to chuck up a small wooden disc or something to take jaw backlash out of the equation. Once you turn a blank, you've trued it up to the true spindle centerline, regardless of how much runout the chuck might have.

For the same reason, I think we can absolve your drive center of any responsibility for the issue you reported.

Regarding dial indicators, do you want "good", or merely "good enough"? I have an indicator and magnetic base from Harbor Freight, about $25 total with a coupon. It's plenty "good enough" for woodworking measurements.

For that matter, since we're aren't really concerned with runout of less than maybe 0.003", for OD runout measurements you could get by with using your tool rest and some feeler gauges. It's merely more tedious to do it that way.

hfmann

Hi RF,

I haven't turned this kind of item yet and I'm not super experienced in turning. But FWIW here's what I found. On items when I did create a tenon to mount in the Nova jaws I had lots of problems. If I remember correctly the tenon is supposed to have the same dovetail profile as the inside of the jaws. Also I believe the tenon is supposed to be short enough that it doesn't touch the bottom of the jaws. Rather the shoulder is supposed to seat firmly and square on the top of the jaws without any space between the jaw and the shoulder. Is that how you do it? If not seated exactly right inside the jaws and solidly on the top, the item can wiggle some. A small catch would always threw it out of kilter for me. I was constantly rechucking and trying to return the item round.

For my projects I switched to using shallow mortises and that works much better for me.

hal

hfmann

PS. I also had some cases where the tailstock mount worked loose. That always caused major problems.

hal

reible

Turning is funny that way. Any small change effects where and how things line up. What you have seen is more or less how it works when going from any form of chucking to another or even for that matter trying to re-chuck parts.

That is why you turn in a particular way from start to finish. You round the stock between centers, but you don't do finishing from there, you instead make gripping points and then part the pieces off. At this point you go to another chuck and it is using what you have done before but from this point on the true centers are likely going to be different. So you again turn, now with the chuck and establish the more finished cuts and sizing of parts. Then at the end you go back and actually turn the outside with the parts in place, and this is the final centering.

If you remove parts from a chuck it very unlikely that you can re-chuck without having the center having moved, even if you take care to mark and try to get everything like it was before. That is why I have two chucks, so I can leave a project chucked rather then taking it off and trying to get it back on, which never really works. Once you have a part off you can expect things to be a little wonky when trying to re-chuck.

Lathe turning is a bit of a different ball game then other woodworking.

Now it could be you have something defective but more then likely just having expectations that are more then reality gives.

Ed

RFGuy

Hal and Ed,

Thanks for your feedback. Really appreciate it. Yeah, I have had some "good" tenons and some problematic ones thus far, so your feedback is well received. I will definitely give more attention to how I construct my tenons and chuck them going forward. Usually, I am doing an interior tenon so the chuck jaws are expanding to hold the workpiece. However, for this method of making salt/pepper mills the chuck jaws are actually contracting so the workpiece is entirely on the inside of the jaws.

So, it sounds to me that re-turning is going to always be required when you change workpiece holding on the lathe. I can't say that I am surprised by this, but it just seems to be excessive the amount of wobble I get between this G3 chuck and my drive hub. I am still tapped out from the holidays, but when I can, I'll buy a magnetic base dial indicator so that I can measure the runout on the Nova G3 chuck. In searching online, it seems that there are quite a few complaints with the Nova G3 chuck in regard to runout. I know you get what you pay for so I may have to consider upgrading in the future to a Oneway, Vicmarc, or similar lathe chuck then sell all the Nova stuff that I bought...

couple links below seem to confirm quality issues and runout/wobble being reported on NOVA chucks:

https://www.forums.woodnet.net/showthread.php?tid=7328867

https://sawmillcreek.org/showthread.php?253775-Aggravated-with-NOVA-chucks

dusty

RFGuy wrote Hal and Ed,

Thanks for your feedback. Really appreciate it. Yeah, I have had some "good" tenons and some problematic ones thus far, so your feedback is well received. I will definitely give more attention to how I construct my tenons and chuck them going forward. Usually, I am doing an interior tenon so the chuck jaws are expanding to hold the workpiece. However, for this method of making salt/pepper mills the chuck jaws are actually contracting so the workpiece is entirely on the inside of the jaws.

So, it sounds to me that re-turning is going to always be required when you change workpiece holding on the lathe. I can't say that I am surprised by this, but it just seems to be excessive the amount of wobble I get between this G3 chuck and my drive hub. I am still tapped out from the holidays, but when I can, I'll buy a magnetic base dial indicator so that I can measure the runout on the Nova G3 chuck. In searching online, it seems that there are quite a few complaints with the Nova G3 chuck in regard to runout. I know you get what you pay for so I may have to consider upgrading in the future to a Oneway, Vicmarc, or similar lathe chuck then sell all the Nova stuff that I bought...

https://www.forums.woodnet.net/showthread.php?tid=7328867

https://sawmillcreek.org/showthread.php?253775-Aggravated-with-NOVA-chucks

Can you tutor me on how you do this and determine that the runout (whatever it is) can be attributed to the G3?

RFGuy

dusty wrote Can you tutor me on how you do this and determine that the runout (whatever it is) can be attributed to the G3?

https://forum.shopsmith.com/viewtopic.php?p=278938#p278938

dusty

If I read into this correctly you are telling me to measure runout with and without the Nova and the difference can be attributed to the Nova.

Can you tell me what runout I should expect on just the spindle?

This is what I see. Is the setup correct and is the number (0.0065") an acceptable runout number? This is the largest number I get as I slowly rotate the spindle.

RFGuy

dusty wrote If I read into this correctly you are telling me to measure runout with and without the Nova and the difference can be attributed to the Nova.

Can you tell me what runout I should expect on just the spindle?

This is what I see. Is the setup correct and is the number (0.0065") an acceptable runout number? This is the largest number I get as I slowly rotate the spindle.

20210114_124523.jpg

Dusty,

Sorry, I missed your reply before. Thanks for measuring this. I still don't have a dial indicator that I can reasonably mount to measure mine yet, but I think your measurement looks reasonable and should be acceptable for a woodworking chuck. In searching some other forums on woodturning, I see differing opinions on the Nova chucks. Some say they are as good as Oneway or Vicmarc chucks and others say that the Nova chucks have excessive runout compared to them. Until I can measure my Nova G3 chuck runout, I am going to just assume that my problem is more to do with the lack of concentricity (differing center points) between my Shopsmith lathe drive hub and the Nova G3 chuck. So, my problem on this thread has more to do with this than with my Nova G3 not meeting a specification, I think. In hunting around on different forums, I did come across a couple of interesting bits of information from more experienced woodturners than myself. When it comes to low runout, highly accurate lathe chucks (metal or woodturning), I believe chucks mounted on a morse taper are more precise than threaded direct drive chucks like the Nova G3. Even with perfectly machined threads, supposedly a morse taper drive is superior to threaded. Related to this apparently the spindle adapter can cause runout issues. To minimize this some woodturners will cut off the end of the spindle adapter so that the shoulder of it rests directly against the backside of the chuck. Also some chucks have a washer between the adapter and the chuck - this washer has to be a precision ground washer so you can't just use a generic one from the hardware store. In looking at my spindle adapter on my Nova G3 chuck there is a gap between the adapter and the chuck so I guess if I wanted to chase this more I could measure runout then try shortening the adapter to see if it helps. Likely would be chasing nits though.

rpd

I note that the links to problems date back to 2017, I believe there was a bad batch of inserts about that time. :)

There is a reference surface on the nose of the insert where it seats into the chuck, it needs to be clean and fully inserted to avoid wobble.

Looking on the Teknatool web site I see that the online Manual for the G3 is not very comprehensive and doesn't seem to mention installing the insert. You can download the manual for the SuperNova2 which covers installing the insert in more detail and has a lot more information.

https://teknatool.freshdesk.com/support/solutions/articles/19000024476-supernova2-chuck-manual-

There is also this trouble shooting manual for their lathes/chucks that might help narrow down the problem.

https://teknatool.freshdesk.com/support/solutions/articles/19000040100-spindle-runout-chuck-wobble-troubleshooting-guide-all-nova-lathes-

RFGuy

rpd wrote I note that the links to problems date back to 2017, I believe there was a bad batch of inserts about that time. :)

There is a reference surface on the nose of the insert where it seats into the chuck, it needs to be clean and fully inserted to avoid wobble.

Looking on the Teknatool web site I see that the online Manual for the G3 is not very comprehensive and doesn't seem to mention installing the insert. You can download the manual for the SuperNova2 which covers installing the insert in more detail and has a lot more information.

https://teknatool.freshdesk.com/support/solutions/articles/19000024476-supernova2-chuck-manual-

There is also this trouble shooting manual for their lathes/chucks that might help narrow down the problem.

https://teknatool.freshdesk.com/support/solutions/articles/19000040100-spindle-runout-chuck-wobble-troubleshooting-guide-all-nova-lathes-

Thanks Ron. Good to know. Hopefully those few bad Nova reviews were just for that bad batch of insert at that time. Thanks for the referral to the Supernova² manual recommendation. When I got my G3 chuck I was surprised how minimal the manual was, but the Supernova² manual is much more detailed and looks useful. I misunderstood where the reference surface is for the insert and the Supernova² manual shows it clearly. Also thanks for the Nova troubleshooting document. I think my G3 is acceptable, but when I get a dial indicator I'll reference these documents and see if I can measure it just to be sure.

rpd

Re the bad inserts, I think that was around the time they shifted production to China, and it was a matter of "You get what you inspect, not what you expect." ;)