My Chuck, And The Saga Continues...

Joe Pitz

Joe Pitz

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

Yes, I am pondering a 4 jaw independent chuck.

Joe
 
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? :)
Click to expand...

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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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.
 
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
 
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.
 
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.
 
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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