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[4]

Taper Turning between centers

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Tinkertoy1941

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#1
This post is for discussion about turning tapers between centers with the dead center in the spindle and the live center OFFSET in the tail stock.
The material to be turned 12L14 with centers made in the lathe chuck with a center drill
The shaft to be tapered being driven with a lathe dog
What are the thoughts on the effects of the male centers being at different angle than the shafts centers affecting concentrically?
Or taking the part out of the lathe to check mating fit with a known tapered sleeve and being able to replace the part on centers exactly from the previous cut?
 

Jimsehr

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#2
I have been thinking about making a tail stock center with a small ball on the end just because of that. The ball rides inside the center.
 

Bobby Bailey

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#3
Tinkertoy
What you are talking about is the standard method.
 

markba633csi

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#4
I believe the angle is limited (not sure what the maximum is, the tailstock is one limiting factor) but yes you can remove and replace the part.
Mark
 

benmychree

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#5
The core is a "bell center drill"; instead of the 60 degree angle, the bell center drill has a curved cutting edge roughly bell shaped; that being said, I have no idea if they are still available, I have only ever see/owned one. I doubt that a small offset such as a Morse taper or similar taper would have much effect on center wear or part geometry.
 

ddickey

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#6
They are still available. Last time I looked Jack Hoying had three for sale.
 

RandyM

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#7
The core is a "bell center drill"; instead of the 60 degree angle, the bell center drill has a curved cutting edge roughly bell shaped; that being said, I have no idea if they are still available, I have only ever see/owned one. I doubt that a small offset such as a Morse taper or similar taper would have much effect on center wear or part geometry.
Yup, still available.

http://www.shars.com/15-hss-bell-type-center-drill-combined-drill-countersink

https://www.amazon.com/KEO-18-Combined-Drill-Countersink/dp/B0034KY7PM

https://www.richardsmicrotool.com/product/802-0018/
 

ddickey

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#8
Also a ball end mill would be a good choice me thinks.
 

Tinkertoy1941

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#9
I think that Jimsehr has the right idea!
My thoughts were to use balls that I have center drilled on the ends of both centers.

Center drill a ball the appropriate size for the center drill in the shaft a drop of Super Glue when setting up should solve any tolerance error.
When done a warm light to soften the glue a little cleanup and ready for the next time
 

Tinkertoy1941

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#10
benmychree said:
The core is a "bell center drill"; instead of the 60 degree angle, the bell center drill has a curved cutting edge roughly bell shaped; that being said, I have no idea if they are still available, I have only ever see/owned one. I doubt that a small offset such as a Morse taper or similar taper would have much effect on center wear or part geometry.

We always called this type of center "Protected Center Drill"
The 60 degree edge was protected from being damaged by the shoulder left when the center drill was drilled about an 1/8" deep from the end of the shaft
 

benmychree

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#11
benmychree said:
The core is a "bell center drill"; instead of the 60 degree angle, the bell center drill has a curved cutting edge roughly bell shaped; that being said, I have no idea if they are still available, I have only ever see/owned one. I doubt that a small offset such as a Morse taper or similar taper would have much effect on center wear or part geometry.

We always called this type of center "Protected Center Drill"
The 60 degree edge was protected from being damaged by the shoulder left when the center drill was drilled about an 1/8" deep from the end of the shaft
Yes, the type illustrated on the sites listed above are not the true BELL type where the whole form that replaces the 60 degree form is curved, not the double angled type illustrated.
 

westsailpat

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#12
McMaster Carr sells a bell center drill .
 

P. Waller

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#13
benmychree said:


We always called this type of center "Protected Center Drill"
The 60 degree edge was protected from being damaged by the shoulder left when the center drill was drilled about an 1/8" deep from the end of the shaft
Exactly, a straight 60 Deg. V with in a counterbore to protect it.

The angles will have little effect unless the taper is great, people have been doing it that way for well over 100 years.

The modern method of turning a taper is to program it (-:
I now run CNC lathes mostly and rarely ever adjust the tail stock, just take a skim cut and measure it then program any taper out, this is a thing of sheer beauty that I never had for 25 years. Once you use a CNC lathe you will never ever want to run a manual again.
 

Tinkertoy1941

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#14
CNC is great!! But I still get a kick out of making details on my foot powered Barnes equipment.
Don't even have to go to the gym.
But as you say CNC makes it easy and the machinist of today will never know the pride of building things the old way before DRO and counting revolutions!!
 

ddickey

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#15
A Toolmakers Ball would work nicely I believe.
 

P. Waller

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#17
But as you say CNC makes it easy and the machinist of today will never know the pride of building things the old way before DRO and counting revolutions!!
Not exactly correct, it does not make it easy merely less tedious.
You may yourself set up a manual lathe/mill operation that virtually anyone can run once configured, you have chosen the work holding methods, the order of operations, the tools, the feeds and speeds, set the stops and adjusted the actual cutting dimensions for the machine used. All that the operator has to do is crank the handles and handle the parts. A CNC or automatic machine does not require an operator.

Think of it as a manual machine that does the laborious handle cranking for you, it will not make the parts itself.
 

Tim9

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#18
Check this YouTube out. Sounds like a good option.

 

magicniner

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#19
CNC is great!! But I still get a kick out of making details on my foot powered Barnes equipment.
Don't even have to go to the gym.
But as you say CNC makes it easy and the machinist of today will never know the pride of building things the old way before DRO and counting revolutions!!
Some different skill sets are required, but those of us who started fully manual, then evolved into DRO users, then added CNC to their abilities know that it's no easier, if you are responsible for maintenance of your own machines and the full cycle from CAD designer through CAM processor to CNC Operator.
It's those who see only the "Operator" bit and haven't learned full 3D CAD/CAM that think CNC makes things easy :D
 
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