# General Question



## jtb51b (Feb 3, 2017)

Should I be able to turn the outside of a piece of stock round on both ends center drill the end away from the chuck and then remove it from a 3 jaw chuck and re-insert it without losing the center? This is on a Logan 200 lathe. I have attempted to adjust the 3 jaw chuck with a dead blow hammer and I cant get anywhere. As long as I start a piece and never remove it I can make fairly decent parts, if I ever remove the work and put it back in its over, it will be out ten thousandths or more!

Thanks for the insight,
Jason


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## Bob Korves (Feb 3, 2017)

The answer to your question is no.  I do not understand what you think a center drill hole will accomplish(?)...  If you have center holes on both ends, and support the work on centers that are true to the lathe axis, then you will not have runout, if done correctly.


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## jtb51b (Feb 3, 2017)

The center hole isn't there for anything other than that's what the piece needs. A center hole. 


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## wa5cab (Feb 3, 2017)

Unless the chuck is an adjustable type like some of those made by Buck, Pratt-Bernerd and others, the only thing that beating on it is going to accomplish is damage to it, the spindle and/or the spindle bearings.


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## jtb51b (Feb 3, 2017)

Didn't beat on it. Just a few tTaps. I have enough sense not to destroy something if it doesn't want to move. So, if I put a work piece that is true in this 3 jaw chuck and it's off, what is the remedy? Jaw grinding? New chuck??


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## jtb51b (Feb 3, 2017)

Say I just need to open the center hole up larger in a bushing, how would I do that if the chuck is off? Hard to turn the center hole larger between centers. 


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## Bob Korves (Feb 3, 2017)

As long as the work is only chucked once and left there, the chuck will not enter into the equation and you will have surfaces true with the axis of your lathe.  As soon as you take it out of the chuck, that concentricity is lost if you try to put it in the chuck again.  Think ahead with your work flow, and plan to do all the work that needs to be accurate in one setup.  It does not matter if the chuck is .020" out and wobbling around as well so long as you cut all surfaces that need to be true to each other in one setup.


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## jtb51b (Feb 3, 2017)

Thanks bob. As long as I keep that in mind I guess I will be ok. Sure would be nice if the chuck were more accurate tho. Are there chucks that are accurate that are reasonably priced? 


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## Bob Korves (Feb 3, 2017)

jtb51b said:


> Thanks bob. As long as I keep that in mind I guess I will be ok. Sure would be nice if the chuck were more accurate tho. Are there chucks that are accurate that are reasonably priced?
> 
> 
> Sent from my iPhone using Tapatalk


There is more accurate, and more accurate yet, and even more accurate than that.  Each increment of added chuck accuracy is due to luck or to $$$, sometimes both.  All chucks will have runout, that is a fact of life.  Good machinists make beautiful and accurate parts with poor tools.  Study their methods and learn from them.  Money does not necessarily buy success, knowledge and skill does...


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## wa5cab (Feb 3, 2017)

OK.  So the hole runs part or all of the way through the part and is not for a dead or live center.  If your chuck has exactly 0.010" runout, and you drill a hole through the part, take the part out if the chuck, and put it back in at random, the hole will have between 0.000" and 0.010" runout, depending upon how close to exactly as it was in the chuck when you drilled the hole the part is when you put it back in.  And assuming that the part is perfectly round.  

If you turn the OD and drill the hole in one sitting, the hole and the OD should be concentric.  For the time being until you sort the 3-jaw problem out, I would suggest that you use a 4-jaw.

EDIT:

If you hold the bushing in the chuck, however you enlarge the bore the ID is going to be off-center by the chuck runout.  

To begin to fix the problem, I would start by removing the chuck and checking for runout on the spindle register.  There shouldn't be any to speak of.  If there is, and if it is consistent, either use a 4-jaw or a much more expensive adjustable 3-jaw.  So long as it makes up on the spindle the same every time, the adjustable 3-jaw will compensate for spindle runout so long as the spindle isn't bent.  

Another solution if the spindle taper has no significant runout and the bushing is small enough would be to use a collet.


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## cathead (Feb 3, 2017)

Jason, 

Consider a 4 jaw chuck.  They are a little more work to true up right off the bat but you get used to it quickly
and find you can do better work.  I have both 3 and 4 jaw chucks and quite honestly, the 3 jaw is
busy collecting dust.  It hasn't seen use for years.  One could drill centers on both ends of a shaft and use a lathe dog
and that would have good repeatability.  It just isn't my style...


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## jtb51b (Feb 3, 2017)

I have a 4 jaw chuck. I will do give it some use and see where I land. Thank you for all the advice. 


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## Bob Korves (Feb 3, 2017)

A four jaw is a life saver when you need to turn your work around and still keep it accurate.  It is still better to do it in one setup if possible, even with a four jaw.


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## darkzero (Feb 3, 2017)

First off, Assuming your spindle runs true. If not or you don't know, start from there.

Since you mentioned tapping on the chuck gives you no improvement, assuming you are loosening the chuck from the adapter slightly when doing so then retighten, I'm assuming your chuck mates the the adaptor's register pretty well. If that's the case as you know  it won't do anything.

Now you can make your chuck an "tap-tru" but it's not recommeneded & I don't recommend it. I've done it to the stock 3-jaw that came with my lathe. But I only keep it around for dirty work like heaving sand, yada yada. I skimmed the register on the adaptor so it was slightly smaller than the register on the chuck. So now it's a loose fit. Now I can tap the chuck to run true. But if you do any heavy cutting or bump it pretty hard, it may run out again. That is why it's not recommened. For light use it will be fine.

Check the runout of your chuck using a a guage pin, shank of an endmill, or even drill rod. I use linear shafting. Remove the piece, chuck it back up & indicate again. Does it repeat your measurement fairly well or is it all over the place? This will tell you if you can just regrind the jaws or if your chuck is very worn.

If it repeats fairly well, what you can do in the mean time (should you decide to try & fix the issue), you might get away with indexing the part before removing it. Say you're working on a piece & you need to remove it for some reason. Mark a line on the part as well as on the chuck. I just use one of the jaws for indexing. When you put it back in the chuck, align the marks & then indicate. You can turn the part CW or CCW to get closer to where you were if off. But again, this only works if your scroll is not worn out.


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## DaveInMi (Feb 4, 2017)

I like the 4-jaw if it needs to be accurate.  If I'm working in the "close enough zone," I mark the piece and put it back in the 3-jaw just the same as it came out.


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## jtb51b (Feb 4, 2017)

Thank you for all the suggestions. Next time I am home I will try out the 4 jaw chuck and learn to use it. I like the idea of marking the work and chuck. I just didn't realize that There would be so much variance in that 3 jaw chuck. I assumed (yeah I know) that these would be fairly accurate chucks. Mine definitely is not. The wobble is visable, and very measurable.  I will start over when I get home. 


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## wa5cab (Feb 4, 2017)

Is the visible wobble that you mentioned of the chuck body or of a nominally round part when it is mounted in the chuck jaws?


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## jtb51b (Feb 4, 2017)

A nominally round part when chucked up. The chuck itself seems to be true. The same part that I had center drilled and turned the outside to size when removed and reinstalled has wobble. So much so that a center in the tailshaft comes no where close to mating up. 


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## wa5cab (Feb 4, 2017)

OK.  With your machined part that you removed and re-mounted in the chuck and found it no longer had no wobble, did you carefully mark it with respect to one of the jaws and then as closely as possible put it back in exactly as it was before you removed it?  If so, the culprit could be wear on the hole in the center of the scroll and/or on the spigot it runs on.  In some cases (the wear needs to be uniform so that the hole and spigot are still round), that can be fixed or at least improved improved upon.  

Have you disassembled, cleaned and inspected the chuck?  I would do so.  With the chuck front body lying on its face and without the jaws, install the scroll on the spigot with no lubricant other than something thin like WD-40 and see whether you can move the scroll other than in rotation.  If you can, you may be able to shim the clearance mostly out.  This may not (probably will not) reduce the runout to near zero but should significantly improve the repeatability.


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## jtb51b (Feb 4, 2017)

Thanks for the help. I did not mark the work I just reinstalled it in the chuck randomly thinking since it was round it would be centered! It will be a couple weeks before I am home to do anything but I will definitely strip the chuck down and clean everything. This lathe lived unused in a wood working shop prior to me buying it. Everything else was covered in sawdust, why not the inside of the chuck! I will definitely look into it. 


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## jtb51b (Feb 6, 2017)

Ok! We are getting somewhere now!! I made it home for one day before heading out for another week or so and I just HAD to take that 3 jaw apart. Man was it full of gritty grease and chips! There were even chips between the chuck and mounting plate! I cleaned everything up, checked for obvious wear as instructed above (found none) regressed and put it back on. I turned a piece of stock between centers the other day and when I chuck it in the 3 jaw now I get very little runout. I have a video of it running I will try to post. Looks much better. How often should I be needing to clean that chuck in that manner?

Thanks again
Jason


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## wa5cab (Feb 6, 2017)

You're welcome.  I didn't expect disassembling the chuck and cleaning it to solve the majority of the problems but I'm glad to hear that it did.

On how often you should do the major cleaning, it's hard to say for an intermittent use machine now in hobby service.  Best that I can guess is every 5 or 10 years.


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## Bill Gruby (Feb 6, 2017)

There is an old school way to keep it close in concentricity when you turn the bar around in the chuck. Mark the bar and the corresponding chuck jaw with a magic marker. When you turn the bar put the mark on the bar and chuck jaw together, That's as close as you can get. Depending on the chuck it can be pretty damn close.

 "Billy G"


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## darkzero (Feb 6, 2017)

It really depends on how oftem you machine & what you machine. I'm just a hobby guy & I fully disassemble my chucks every year or 2. However I do often remove the jaws to clean the chips out of the scroll. You can usually feel them when they get in there.

If I do any heavy sanding or machine nastier stuff like cast iron, fiberous composites, etc, or even just showering it from fine chips, I'll take the jaws out & clean it right after. I have a dedicated chuck that I use whenever I do heavy sanding, etc. That dust gets sucked right in there when the chuck is spinningbat moderate speeds.


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## jtb51b (Feb 6, 2017)

Great. That gives me an idea of when to take a look at it. It was really embarrassing just how much junk and funk was in there. Life in a wood shop is rough on oily things! I will DEFINITELY clean the 4 jaw before I do anything with it. It's probably just as bad.  I now understand that I am not going to get a perfect setup every time I remove and reinstall the work but it was way off! It's not perfect now but it's close enough to make me feel better. I imagine if I mark my work and reinstall with the marks I will be much better off.  Thank you again for all the help. 

Jason


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## Bob Korves (Feb 6, 2017)

Use oil instead of grease in the chuck and it will not attract and retain as many chips.


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