On Tuesday, December 12, 2017 at 7:40:45 PM UTC-5, John B. wrote:
On 12 Dec 2017 21:31:53 GMT, "DoN. Nichols"
wrote:

On 2017-12-11, Bob La Londe wrote:

I watched one the other day that was a sort of interesting trick for
turning tapers "between centers." You put a boring head in the tail
stock. For low angle tapers you can just put a center in the boring
head, and for sharper angles you can use a cup with a ball bearing in
the chuck and the boring head. I get all of that and it makes sense.
What got me and the guy makign the video didn't show (or I missed it) is:

How do you make sure the center or ball bearing cup in the boring head
is on center vertically?

Perhaps put a level on the dovetail with it extended a bit?

Since I don't have to turn a lot of tapers I thought this might be a
nice stop gap technique instead of making a taper attachment for my lathe.

Many (though not all) lathes have provisions for offsetting the
tailstock to do taper turning between centers. You loosen the tailstock
clamp to the bed, loosen a screw in the middle of the back side of the
tailstock, and tighten the one in the front side to move the tailstock
ram back. (Or the other way around, to move it towards you, depending
on whether you want the big end of the taper towards the tailstock or
the headstock.) With this, there is no question as to whether the
height of the center is correct.

However, you need to come up with a way to set the tailstock
back on horizontal center when you are done. There are various tricks
for this.

The two lathes which I have had which do not have this feature
are the Unimat SL-1000 (on that, you rotate the headstock to shift the
tip back or forward), and the Emco-Maier Compact-5/CNC, which being a CNC
lathe, can do tapers without the trick. However, the same tailstock is
used on the manual Compact-5, so there such a trick would be useful.

Enjoy,
DoN.


To align head and tail centers you simply mount a piece of stock
between centers and turn a length at the head stock end and then at
the tail stock end - using the same cross feed setting of course.
Adjust the tail stock, if necessary and repeat.

They used to sell "test bars" to do this. Hardened steel bars to be
mounted between centers and then you could mount a dial indicator on
the carriage and run the carriage back and forth. The test bars were,
of course, exactly the same diameter for their entire length.

Back in the day, they weren't considered "tricks". Just common
knowledge in the trade :-)
--
Cheers,

John B.

A fishtail gauge (or any piece of flat stock) pinched between the centers will quickly indicate any misalignment.