Rotary table tail stock question...

[cathead]

I have a 12 inch rotary table that has a tail stock for mounting shafts on centers.
The tail stock is not a simple 60 degree center but the point is offset upward
about 1/8 inch from the top of the tail stock shaft. There must be a reason that
a simple cone center is not used. I can see no advantage in this but would like
to know the answer as I am building a shorter version to mount shafts using my
spin index. What is the advantage in an offset center???ondering:

 

[Wreck™Wreck]

Are you sure that it is offset? Some dead centers are notched to allow the tool to get closer to the center of the part on the tool side.
Also called a half center by some.

 

[Reeltor]

I don't have a tail stock for my RT but I do have one that came with my dividing head. The top of the center is machined flat for access like Wreck mentioned. The tail stock is adjustable both in height and for angle. You said that the point is offset upwards, is there a bolt that you can loosen and change that angle?

I'll see if I have a photo of my tail stock, and add it if I do.

Mike

 

[Reeltor]

I found a photo of my van norman dividing head tail stock and a schematic for Brown and Sharp head and tail stock. Now, let's see if I can upload them :thinking:
The upload appears to have worked, you can see the curve of the housing, loosen the large center nut and the rear nut to allow the center to pivot. Loosen all three nuts to move the entire dead center up or down. This center was so gummed up with old grease that I wouldn't have believed that there was any adjustment possible. Maybe yours is too.
The B & S drawing is a pdf for reference.
I hope this helps you out,

View attachment PAGE 7 brownsharpe-dividing-heads-types012.pdf

 

[Wreck™Wreck]

Like this I imagine, adjusted in myriad ways.
http://www.millerstooling.com.au/cmsimages/Indexing Heads 05.jpg

 

[cathead]

Like this I imagine, adjusted in myriad ways.
http://www.millerstooling.com.au/cmsimages/Indexing Heads 05.jpg

The millerstooling.com photo above shows a tail stock with a conventional 60 degree
dead center. The VanNorman one that Reeltor posted has the offset center.
I see no advantage in the offset center as either configuration provides equal
access to a machining tool.

However, there must be a reason the VanNorman tail stock was made that way
offset from center.

I'm not interested in making adjustments to the tail stock. I am only interested
in finding out what could possibly be the advantage to a non-concentrical center.



Also for clarity, I am not refering to a half center, only to an off set center.

 

[f350ca]

I believe they offset the centre for tool clearance. If you were say cutting a keyway it gives room to come in from the end without hitting the centre.

Greg

 

[cathead]

I believe they offset the centre for tool clearance. If you were say cutting a keyway it gives room to come in from the end without hitting the centre.

Greg

OK, that makes sense. I have been mulling this over all day unable to come up with
a reason. Thanks for the input.:thumbzup3:

 

[Reeltor]

I believe they offset the centre for tool clearance. If you were say cutting a keyway it gives room to come in from the end without hitting the centre.

Greg

100% agree, even more important to have clearance when using a horizontal wheel to cut the keyway.

Mike

 

[Wreck™Wreck]

Also for clarity, I am not refering to a half center, only to an off set center.

I posted the first picture that turned up on the web, what advantage would be gained with a center with an offset?
I am all ears.