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Yep, measure measure measure
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Sorry guys, backplate again.
- Thread starter snoopdog
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- Dec 27, 2021
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I am, the 3jaw turned out good, other than the snafu with one of the bolt holes. I don't want to have to solve a problem like that again, if I can help it. I believe it was caused by the pins that I machined in lieu of transfer screws or punches, I have a set of punches now. Had to polish the oxide off, and ream the bolt holes on this one to get a good fit. If I get home on time tomorrow, I will start cutting, probably.
- Joined
- Sep 14, 2014
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- 794
Just a couple of comments. Hope I'm not restating the obvious, if so, sorry.
In this thread you didn't mention the lathe brand, but I understand a 9" South Bend has a 13/16 long spindle from the registration face. A Logan 10" has a 1" in length spindle.
"Registration face" is, I understand, the proper term for the shoulder at the base of the spindle closest to where the spindle enters the headstock.
A properly fitting chuck must have the back face of the one piece or "uni" chuck, or the back of the back plate, seat on the registration face. A tightly fitting bore to the spindle is very good, but more important is that the chuck seat on the registration face. Bottoming out on the spindle nose is not good.
A chuck first fitted to a South Bend must be modified to work on a Logan, or a spacer used so the chuck hits the registration face and doesn't bottom out on the end of the spindle. I learned this when I purchased a Logan and was trying to figure out why I was having so much run-out when spindle, bearings, tail stock. all seemed to check out. The back plate on the Bison chuck had a bore that was ~ 1/8" too shallow. The back plate was bottoming out on the spindle nose.
What ever length spindle the manufacturer made is what they figured would work. I know wayyyy less than many, but I did wonder if the lathe was made for a face plate and nothing more hanging off the spindle. Probably not, just a thought. Myself I wouldn't be bothered one bit with the spindle length as long as the chuck seats properly.
Once seated to the registration face, the chuck is rigid to registration face. The spindle fit becomes secondary. When the bore is too shallow, as mentioned, a spacer can be used to a gap.
Ron
In this thread you didn't mention the lathe brand, but I understand a 9" South Bend has a 13/16 long spindle from the registration face. A Logan 10" has a 1" in length spindle.
"Registration face" is, I understand, the proper term for the shoulder at the base of the spindle closest to where the spindle enters the headstock.
A properly fitting chuck must have the back face of the one piece or "uni" chuck, or the back of the back plate, seat on the registration face. A tightly fitting bore to the spindle is very good, but more important is that the chuck seat on the registration face. Bottoming out on the spindle nose is not good.
A chuck first fitted to a South Bend must be modified to work on a Logan, or a spacer used so the chuck hits the registration face and doesn't bottom out on the end of the spindle. I learned this when I purchased a Logan and was trying to figure out why I was having so much run-out when spindle, bearings, tail stock. all seemed to check out. The back plate on the Bison chuck had a bore that was ~ 1/8" too shallow. The back plate was bottoming out on the spindle nose.
What ever length spindle the manufacturer made is what they figured would work. I know wayyyy less than many, but I did wonder if the lathe was made for a face plate and nothing more hanging off the spindle. Probably not, just a thought. Myself I wouldn't be bothered one bit with the spindle length as long as the chuck seats properly.
Once seated to the registration face, the chuck is rigid to registration face. The spindle fit becomes secondary. When the bore is too shallow, as mentioned, a spacer can be used to a gap.
Ron
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