Re: trouble between centers
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I’m not very experience at machining but I will give you my thoughts.
We know that all factors of turning are the same except for the way the part is mounted.
Same tool bit
Same piece of stock
Same feeds & Speeds
Same cutting oil (if used)
Same live/dead center in the tail stock
Making some assumptions, by lousy finish you mean a rough surface. Also you are not getting any chatter.
The only difference is the part is either turned using a chuck (3 jaw) or Dog. When the part is in a chuck, it is firmly clamped. When held between centers the part is squeezed and turned by a dog that “floats” with rotation. I don’t understand why that would make a difference but I would start looking there.
Try putting in a dead center clamped in the chuck. True up the point then see if you get a better finish.
Do the same with a dead center mounted directly in the spindle.
Check your live center in the tail stock. If you have a different one try it.
You may also try a dead center in the tail stock.
Do each of these one at a time and you will be able to hone into what your problem is.
Good luck to you.
From: SOUTHBENDLATHE@... [mailto:SOUTHBENDLATHE@...]
Sent: Friday, December 11, 2015 7:31 AM
Subject: Re: [SOUTHBENDLATHE] trouble between centers
Thanks for all the advice. The thing that I don't understand is that I get a great finish with the work in a chuck at the headstock, and a lousy finish with the work between centers with a dog, and all other conditions exactly the same.