Thread: 3 jaws chuck runout questions

Hi Peter,

I'd be happy with the 0.04mm at 50mm dia.
Is there still 40" runout out at 25mm?

Stuart

Originally Posted by Stustoys

Hi Peter,

I'd be happy with the 0.04mm at 50mm dia.
Is there still 40" runout out at 25mm?

Stuart

Morning Stuart.
no i haven't test the 25mm dia agian after mucking around with the adjustment . i stop testing after i did the 50mm dia bar .
Cheers
Peter

40 inch runout?

Dean

Originally Posted by Oldneweng

40 inch runout?

Dean

haahaha.
gota love this runout does it .

Stuart .
i got same result with the 25mm dia bar so i'm happy with that.
Peter

Hi Peter,

Good news.

Originally Posted by Oldneweng

40 inch runout?

Oops, thats what happens when I use old peoples numbers

Stuart

Originally Posted by thorens

Hi Jodan.
after muck around with it. I get it down to 0.04mm runout on the 50mm bar .
should i try more ?
Peter

Hi Peter, I presume that you mean 0.4 mm, and not 0.04 mm, because if you only have 0.04 mm runout, and if it is consistently close to that figure over a good range of shaft diameters, you have a better chuck than most. 0.04 mm equates to just over one and a half thou, which is better than many collets would achieve.
On the other hand 0.4 mm is just under 15 ¾ thou, and a more likely result for an inexpensive Chinese made chuck, especially if there was any imperfection in its assembly to backing plate and headstock.
If the runout is reasonably consistent in amount and and direction (for example between 12 and 16 thou, towards jaw No.2 say) when chucking a large range of diameters, you could modify the chuck and maybe also the backing plate to make your own version of a Set-Tru chuck, and you would be able to dial it in much closer. In all probability though, the runout will vary somewhat, possibly both in magnitude and direction, so it might not be worthwhile unless you make multiple parts from identical stock, when you could dial the chuck in for that size stock, and have the convenience of the 3 jaw with near the accuracy of the 4 jaw chuck.
There has been lots of discussion on this subject, in many forums over the years, and Google will point you to them, but I have put a couple of links in which may be of interest if you want to tune your chuck up a bit more, that is if it has runout of 0.4mm, if it only has runout of 0.04mm, you want to guard it well, and only feed it with bright bar or previously machined workpieces, or else you will soon loose that accuracy.
The first 2 links are to examples of home brewed "Set-Tru" type chucks, and the last link is to the manual of the Asian made South Bend adjustable chucks, hope you find it useful'
Rob.
HomeShopTech

New (to me) chuck, and making a backplate - Home Model Engine Machinist

http://cdn0.grizzly.com/manuals/sb1314_m.pdf

Originally Posted by Ropetangler

Hi Peter, I presume that you mean 0.4 mm, and not 0.04 mm, because if you only have 0.04 mm runout, and if it is consistently close to that figure over a good range of shaft diameters, you have a better chuck than most. 0.04 mm equates to just over one and a half thou, which is better than many collets would achieve.
On the other hand 0.4 mm is just under 15 ¾ thou, and a more likely result for an inexpensive Chinese made chuck, especially if there was any imperfection in its assembly to backing plate and headstock.
If the runout is reasonably consistent in amount and and direction (for example between 12 and 16 thou, towards jaw No.2 say) when chucking a large range of diameters, you could modify the chuck and maybe also the backing plate to make your own version of a Set-Tru chuck, and you would be able to dial it in much closer. In all probability though, the runout will vary somewhat, possibly both in magnitude and direction, so it might not be worthwhile unless you make multiple parts from identical stock, when you could dial the chuck in for that size stock, and have the convenience of the 3 jaw with near the accuracy of the 4 jaw chuck.
There has been lots of discussion on this subject, in many forums over the years, and Google will point you to them, but I have put a couple of links in which may be of interest if you want to tune your chuck up a bit more, that is if it has runout of 0.4mm, if it only has runout of 0.04mm, you want to guard it well, and only feed it with bright bar or previously machined workpieces, or else you will soon loose that accuracy.
The first 2 links are to examples of home brewed "Set-Tru" type chucks, and the last link is to the manual of the Asian made South Bend adjustable chucks, hope you find it useful'
Rob.
HomeShopTech

New (to me) chuck, and making a backplate - Home Model Engine Machinist

http://cdn0.grizzly.com/manuals/sb1314_m.pdf

hello Rob.
you might got me on this
i was using the 0.01mm~10mm Mitutoyo dial indicator and the runout was 4 marks on the dial . so i thought it means 0.04mm ? or i'm was wrong ?
the whole dial have 100 marks in ten sections .
thanks for the links.i will have some reading tomorrow .
also the process i did was re-machine the back plate so it run true on the lathe and then re-install the chuck when i re-machine the back plate i give the register a few thous smaller than before so i can have some to adjust and it did what i wanted to .
regards
Peter

Originally Posted by thorens

hello Rob.
you might got me on this
i was using the 0.01mm~10mm Mitutoyo dial indicator and the runout was 4 marks on the dial . so i thought it means 0.04mm ? or i'm was wrong ?
the whole dial have 100 marks in ten sections .
thanks for the links.i will have some reading tomorrow .
also the process i did was re-machine the back plate so it run true on the lathe and then re-install the chuck when i re-machine the back plate i give the register a few thous smaller than before so i can have some to adjust and it did what i wanted to .
regards
Peter

Hi Peter, That does sound like your dial indicator reads to 0.01 mm, I assume that the needle rotates 10 times to measure the 10 mm. I would also expect that it has a secondary dial which counts full revolutions of the needle on the main dial like the one in this link. If your chuck is consistently giving results anything like those you have reported, it is much better than you would normally expect, and well worth taking extra good care of IMO. Cheers,
Rob

Google Image Result for http://www.powertoolsdirect.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/m/i/mitutoyo-2047s-dial-indicator-0-01mm-grad.jpg

Originally Posted by Ropetangler

Hi Peter, That does sound like your dial indicator reads to 0.01 mm, I assume that the needle rotates 10 times to measure the 10 mm. I would also expect that it has a secondary dial which counts full revolutions of the needle on the main dial like the one in this link. If your chuck is consistently giving results anything like those you have reported, it is much better than you would normally expect, and well worth taking extra good care of IMO. Cheers,
Rob

Google Image Result for http://www.powertoolsdirect.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/m/i/mitutoyo-2047s-dial-indicator-0-01mm-grad.jpg

Hi Rob.
yes i can confirm that my dial indicator is a 0.01mm type dial . it is an older type compare to the one you linked .
regards
peter

Originally Posted by thorens

ok.
so i think what I'm getting out of this chinese 3 jaws chuck is as good as it going to get then.
Thanks
Peter

Hi Thorens,
I would have liked to get less runout but 1.5thou is good enough for me. If I really want to be precise I use the original Prat Burnard chuck. I get less than half a thou consistently from that one. FWIW the only reason that I bought a 125mm chuck was because I have lost the outside jaws for the PB chuck and needed to be able to hold an 80mm dia workpiece for another job.
PB can supply a new set of jaws for the original Myford chuck at the expense of both arms and legs !!!.

I don't think that there is a lot to choose between Indian and Chinese chucks. In my case I think someone screwed up and mixed up the jaw sets between two chucks, particularly since the serial numbers were different. One last criticism both the new chucks do not have the jaw position marked ! I like to know which slot each one lives in.

You can always do a test fit of the jaws in different positions until you find the best fit. There are only 3 possible fitments, the jaws still have to be placed in the correct order. Once the most true setup is found, back em out and stamp the chuck.

Originally Posted by BaronJ

Hi Thorens,
I would have liked to get less runout but 1.5thou is good enough for me. If I really want to be precise I use the original Prat Burnard chuck. I get less than half a thou consistently from that one. FWIW the only reason that I bought a 125mm chuck was because I have lost the outside jaws for the PB chuck and needed to be able to hold an 80mm dia workpiece for another job.
PB can supply a new set of jaws for the original Myford chuck at the expense of both arms and legs !!!.

I don't think that there is a lot to choose between Indian and Chinese chucks. In my case I think someone screwed up and mixed up the jaw sets between two chucks, particularly since the serial numbers were different. One last criticism both the new chucks do not have the jaw position marked ! I like to know which slot each one lives in.

i'd love to get my hand on the PB chuck if any one here have one for sale ? i looking for the 8" , D4 mount should be good .
cheers
Peter