# My Chuck, And The Saga Continues...



## Joe Pitz (Jul 28, 2015)

Hello All, 

I must have measured my TIR incorrectly.  I went back and measured again as I need to center my tailstock.

I found that the chuck was out of TIR .015"  I did some more measuring and found out that one of the master jaws, #2 was .011 too low.  Looks like the scroll is warn.  So since the jaws are soft steel I used a carbide boring bar to take some clean up cuts on the new chuck jaws.  That is of course after putting some round stock in the master jaws and tighten the chuck down.  (The new top jaws are lower than the master jaws.

I also loosened the adapter plate and tapped on the chuck jaws and was able to bring the TIR back down to .005"

Now the question would be, is .005" an acceptable TIR, or should I purchase a shars chuck?

Then the question would be, should I go for another 6" 3 jaw scroll chuck or upgrade to an 8" 4 jaw chuck?

Is there a need for both a 4 jaw and a 3 jaw scroll chuck?

Who is the one who told me that machining was an inexpensive hobby?  

Thanks

Joe


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## f350ca (Jul 28, 2015)

Joe, after you made the clean up pass on the jaws there should be no runout, at least at that dia.
When you say the new top  jaws are lower do you mean they close smaller than the masters? If not they won't allow you to hold long stock.
0.005 runout is on the high side but not unusable. If you are making a part and don't remove the stock from the chuck the runout disappears after your first pass. If you need to stay concentric to existing features or turn the part around you need a 4 jaw independent chuck, then you can adjust the run out.
There are no doubt times when a 4 jaw scroll chuck would be of use, but I've never needed one. For round stock unless its ground perfectly circular four jaws aren't likely to all grab evenly and the stock could move.

Greg


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## Joe Pitz (Jul 29, 2015)

Thanks Greg, yes the top jaws close smaller than the masters.  

Yes, I am pondering a 4 jaw independent chuck.

Joe


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## JimDawson (Jul 29, 2015)

Joe Pitz said:


> Then the question would be, should I go for another 6" 3 jaw scroll chuck or upgrade to an 8" 4 jaw chuck?
> 
> Is there a need for both a 4 jaw and a 3 jaw scroll chuck?
> 
> Who is the one who told me that machining was an inexpensive hobby?



I would go with a 6 inch, 3 jaw scroll and a 8 inch, 4 jaw independent.  Each has it's use and will add flexibility to your lathe and projects.

Machining is a much less expensive hobby than airplanes or boats, and you have a chance of recouping some of your investment. 
.
.


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## Joe Pitz (Jul 29, 2015)

As always, thanks Jim for the good advise.

Thanks

Joe


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## Tozguy (Jul 29, 2015)

A 3 jaw scroll chuck is the workhorse and often suffers from over-tightening and other abuse. A worn one can get frustrating. The idea of getting a new one and reserving it for lighter/more precise work might make sense if it suits your needs.
A 4 jaw independent chuck is more versatile but is less convenient. As Greg mentioned it might be necessary to grind the jaws to get the best out of it.
I would not want to be without either one.


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## Joe Pitz (Jul 29, 2015)

Thanks Tozguy,  Since the jaws are soft I did turn the jaws with several clean up cuts.  Greg indicated that the jaws would be true at the given diameter.  When I changed the diameter to check the TIR, that seemed to change the TIP again.

Joe


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## JW714 (Jul 29, 2015)

Hey Joe I'm far from an expert but, in my experience buy a good chuck. I bought a Bison years ago and it is a pleasure to use.


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## neshkoro (Jul 29, 2015)

It all depends on the parts you are making and the accuracy required. .005" run out is quite a bit. It's nice and much less time consuming to have an accurate chuck that you don't have to monkey around with each time you chuck up a part. Just put the part in the chuck and tighten it down. It should be within .001 or .002". A 4-jaw chuck has its uses; mostly for holding parts that are not round or for rechucking something that requires much accuracy.


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## Joe Pitz (Jul 29, 2015)

Thanks JW,  I will take a look at Bison,  But I will probably have a fit on the price  
But you are correct, you get what you pay for.

Joe


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## Joe Pitz (Jul 29, 2015)

Thanks neshkoro for the good info.

Joe


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## chips&more (Jul 29, 2015)

Sorry to hear your frustrations. Trying to save a worn chuck will typically not yield results that are rewarding. A chuck with a worn scroll or bell mouthed jaws for example is typically restored by grinding on the jaws? I will not get into it but just think about it. Are you fixing the root of problem or just a Band-Aid fix? The chuck is the heart of the lathe. I would get the best new chuck you can afford. I would get a 3 jaw with the set true feature. And like mentioned, having two chucks, one for the precise work and one for the dirty jobs is an excellent idea. Putting a part in the lathe and having it run within say 0.001” makes life much easier. Get a good chuck…Good Luck, Dave.


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## Doubleeboy (Jul 29, 2015)

Enco's Interstate chucks are not bad, and if you get a lame one the return shipping is free, no problems.  Not the quality of Bison but likely less than half the cost.  There was a time when Bison was only 10 or 20% more than the Chinese stuff, sadly those days are gone.   I would avoid Gator at all cost, rubbish IMO.   I have a 8" 6jaw Set Tru from them that makes my no name Chinese budget 4 jaw look like a bargain.

michael


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## Joe Pitz (Jul 29, 2015)

Thanks Chips &more,  yes, I have been messing around with this chuck a lot.  I am considering getting a new chuck

Joe


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## Joe Pitz (Jul 29, 2015)

Thanks Michael,  I am looking on ebay and there is a Bison 6" new,  I will also check out the Enco chuck you recommend.

Joe


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## Doubleeboy (Jul 29, 2015)

Joe, in fairness to any of the import chuck manufacturers, its a crap shoot, this week good, next week maybe not so much.   My enco branded set tru 3 jaw for my 10ee is great, very close to Bison, only costs me 300 dollars 1o or so years ago.   The Gator, looked okay, but one top jaw took hours of my fiddling to get to remove and reinstall worth a damn.  Grit everywhere inside of chuck.  Like I mentioned before if you get crap from Enco, if you call and explain nicely the situation, they will have UPS come and take it away and in a week or so your money is refunded.

I also have a variety of small to medium size Bison chucks, they are great but have doubled to tripled in cost in last 12 years.  I would be hard pressed to buy another. Luckily given my age I will not have to buy another.

cheers
michael


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## Tozguy (Jul 29, 2015)

A scroll chuck will not give the same TIR at all work diameters even when new and much less when worn.
Have you tried each of the key pinions to see which one gives the best TIR?
Chuck run out is not always an issue. As already mentioned if you can do all the turning without removing the work it will be fine.
What practical limitations have you encountered so far with the chuck you have?



Joe Pitz said:


> Thanks Tozguy,  Since the jaws are soft I did turn the jaws with several clean up cuts.  Greg indicated that the jaws would be true at the given diameter.  When I changed the diameter to check the TIR, that seemed to change the TIP again.
> 
> Joe


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## Joe Pitz (Jul 29, 2015)

Thanks Michael,  I made an offer to a guy on ebay for a new Bison 6" 3 jaw scroll chuck for $400.  He accepted.  I had to swallow hard when I made that payment.  But hopefully my chuck troubles are behind me
and I can continue getting my lathe up to speed for turning.

Joe


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## Joe Pitz (Jul 29, 2015)

Tozguy:

"Have you tried each of the key pinions to see which one gives the best TIR?"

Not sure what that is?

If you are talking about the steps on the outside of the jaws. my current chuck does not have any.  I was going to mill the slots but now I do not have to.  Will keep the soft jaws for special projects.

Thanks

Joe


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## Joe Pitz (Jul 29, 2015)

Michael, when I get ready to purchase the 4 jaw 8" I will more than likely try the Enco that you recommend.  but that will be a while.

Thanks

Joe


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## Tozguy (Jul 29, 2015)

Not sure that 'key pinion' is the right term but its the socket that the chuck key goes into to turn the jaws in or out. There are three sockets on my scroll chuck. Only need to use one of the sockets to open or close the jaws. It is recommended that each of the pinions be tried with a TIR measurement to see which socket gives the lowest result. Of course if a scroll chuck has only one key pinion this doesn't apply.


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## Joe Pitz (Jul 29, 2015)

Thanks Tozguy,  my chuck has three as well,  I tried two when I was measuring. I will try all three and see what happens.

Joe


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## Wreck™Wreck (Aug 3, 2015)

I use a set tru Bison 3 jaw scroll chuck nearly every day, 5-6 days per week, I change the top jaws several times per day on an average day. We have 40+ sets of soft jaws labeled for either recurring jobs or by diameter between 2 lathes. 

Put the jaws on, chuck a piece of like sized material, (turn it so that is reasonably round first) indicate and adjust the chuck to whatever tolerance is required, expect .002-.005 TIR runout between parts as anything else is asking entirely too much of a scroll chuck. With practice adjusting the chuck will take less then 10 minutes unless you suffer from crippling OCD of course (-:


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## Joe Pitz (Aug 3, 2015)

[QUOTE="
Put the jaws on, chuck a piece of like sized material, (turn it so that is reasonably round first) indicate and adjust the chuck to whatever tolerance is required, expect .002-.005 TIR runout between parts as anything else is asking entirely too much of a scroll chuck. With practice adjusting the chuck will take less then 10 minutes unless you suffer from crippling OCD of course (-:[/QUOTE]

Thanks Wreck Wreck,  How do you adjust the jaws on a scroll chuck?  Regardless of which chuck key hole I try to adjust, the TIR error is the same?

Joe


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## T Bredehoft (Aug 3, 2015)

Joe Pitz said:


> Tozguy:
> 
> "Have you tried each of the key pinions to see which one gives the best TIR?"    Not sure what that is?



Sometimes, each position where you can put the chuck wrench, can influence the run-out (TIR) differently. Put a dowel pin in the chuck and tighten it. mark the wrench position as No. 1, and check the TIR.  Do the same for each position, compare and use the best one.


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## Joe Pitz (Aug 3, 2015)

Thanks Tom, I will give that a try.

Joe


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## Wreck™Wreck (Aug 3, 2015)

Joe Pitz said:


> [QUOTE="
> Put the jaws on, chuck a piece of like sized material, (turn it so that is reasonably round first) indicate and adjust the chuck to whatever tolerance is required, expect .002-.005 TIR runout between parts as anything else is asking entirely too much of a scroll chuck. With practice adjusting the chuck will take less then 10 minutes unless you suffer from crippling OCD of course (-:



Thanks Wreck Wreck,  How do you adjust the jaws on a scroll chuck?  Regardless of which chuck key hole I try to adjust, the TIR error is the same?

Joe[/QUOTE]
You must have an adjustable chuck, you are adjusting the entire chuck body not the jaws themselves, Set Tru is a brand name owned by one of the chuck manufacturers, I am not sure which one.
Adjusting a set tru chuck is exactly like putting a scroll chuck in a 4 jaw independent chuck and dialing out the runout with the independent chuck, the errors in the scroll will remain however. If you require tenths accuracy dial in each part and finish it in one chucking, or stop chasing tenths (-:

I only chase tenths when I know that the Customer has the ability to measure it and the part requires it.

I routinely get drawings for lathe parts from one particular customer  with dimensions like so (last weeks parts, a counterbore) .8749-.8744, .213 deep +- .002.
There is zero chance that anyone at this company can measure this, or would even try, chasing tenths will drive you mad so don't do it.


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## Joe Pitz (Aug 3, 2015)

Wreck Wreck,  I am confused now.  I will include some pics of my chuck.  both front view and back view.
I do not think I have a Set Tru Chuck.  

Thanks

Joe


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## JimDawson (Aug 3, 2015)

Joe, I can understand your confusion.  Adjust-Tru chucks are adjusted on the register with set screws, not with the scroll.  This allows compensating for inaccuracies in the scroll.
.
.


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## Wreck™Wreck (Aug 3, 2015)

Joe Pitz said:


> Wreck Wreck,  I am confused now.  I will include some pics of my chuck.  both front view and back view.
> I do not think I have a Set Tru Chuck.
> 
> Thanks
> ...


An adjustable chuck has a loose fitting rabbet, (or register if you prefer that nomenclature)  and 4 tapped screw holes arranged radially around the circumference, loosen the screws that hold the chuck body to the back plate, use an indicator on the part (in the jaws) and adjust the the 4 radial screws exactly like an independent 4 jaw chuck until you reach your required level of accuracy. Tighten the screws and machine away. Please note that these chucks will only  correct .020-.030" of error, if more offset is required just use an independent chuck.


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## Joe Pitz (Aug 4, 2015)

Thanks Jim and Wreck Wreck.  Makes sense now that you explain it.  I will keep an eye out for them. 

Joe


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