What is the "tailstock offset method" of turning a taper?

[Tony Wells]

One aspect of taper turning between centers that is often overlooked is the problem of 60 degree center holes and 60 degree centers. Once you leave spindle centerline, all the angles that were correct while on spindle center are now wrong, and no longer symmetrical with the spindle axis. Some people use spherical centers to combat this problem. There are bell shaped center drills that make up for small angular differences that allows the use of standard center, but not usually enough for steep tapers.

Also, when dialing in a taper with an indicator and a straight reference bar, be sure the indicator is as close to center height as possible so you don't introduce errors. Same when using an existing tapered part such as Morse drill shank to indicate your offset. Make sure the indicator's plunger is parallel with the cross-slide ways. Otherwise you will introduce sine errors.

 

[churchjw]

We have an article on the site about this one. http://www.hobby-machinist.com/cont...apers-on-lathe-using-tail-stock-offset-method There are a lot of drawbacks to doing it. Especially the one Tony is talking about. If you have a taper attachment that is is a much better way to go.


Jeff

 

[irishwoodsman]

this works for me:biggrin:mac just remember to measure your offset at the end of your stock at the tail section:thinking:mac

 

[george wilson]

Hopefully Nelson,you will see this. There are special center drills for drilling the hole in the end of metal that you are going to turn a taper on using the offset tailstock method. They are not ground with STRAIGHT 60º angles on them,but are ground shaped like the bell mouth of a trumpet,with the little drill point still in the center.

These assure 100% contact of the dead center all the way around the hole,when the metal is at an angle to it. Use of the normal center drills provides ONLY contact at 2 places in the center drilled hole. The metal could manage to go up and down a bit because of this 2 point only contact.

I've used normal center drills when turning tapers back when I didn't know better,but the trumpet shaped center drills are really the best.

 

[ScrapMetal]

I'm kind of surprised that there isn't an offset tailstock center like the kit above with a provision for angling the center point for a more secure fit and less wear. Something along these lines:



-Ron

 

[irishwoodsman]

i've not had any problems on wear as long as you use a center and dogs on other end and a drop of oil every so often and run your tool down the stock to make sure she is centerd good to the axes:biggrin:mac

 

[Nelson]

Hopefully Nelson,you will see this. There are special center drills for drilling the hole in the end of metal that you are going to turn a taper on using the offset tailstock method. They are not ground with STRAIGHT 60º angles on them,but are ground shaped like the bell mouth of a trumpet,with the little drill point still in the center.

These assure 100% contact of the dead center all the way around the hole,when the metal is at an angle to it. Use of the normal center drills provides ONLY contact at 2 places in the center drilled hole. The metal could manage to go up and down a bit because of this 2 point only contact.

I've used normal center drills when turning tapers back when I didn't know better,but the trumpet shaped center drills are really the best.

George,

I certainly will- might take me a day or two. I bought a set of three (3) center drills. I hope that will be enough. I suspect I will need more.

I copied this thread for reference. I have a nice selection of reference materials for when I get things going.


Thanks!


:tiphat:Nelson

 

[irishwoodsman]

I'm kind of surprised that there isn't an offset tailstock center like the kit above with a provision for angling the center point for a more secure fit and less wear. Something along these lines: that would be nice but i wonder what the stability would be like:thinking:mac



-Ron

that would be nice but i wonder what the stability would be like:thinking:mac

 

[george wilson]

Actually,I did not see that Tony Wells had already mentioned the correct center drills for taper turning.

 

[ScrapMetal]

that would be nice but i wonder what the stability would be like:thinking:mac

That was just an "off the top of my head" sketch for conversatios sake. I've already thought out another half dozen designs that would be more practical and stable.

-Ron