Turning Between Centers W/ Ball End Centers.

SoIll914

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I find myself doing alot of work between centers and have heard about ball centers and i think im going to set up my own. from what i understand(feel free to correct me) a ball center is better suited to tailstock offset turning because it has more radius to allow the offset to stay aligned where you want it. as opposed to 60 degree dead or live centering both ends which is designed for dead straight alignment. SO my questions are, should i/could i just use a ball on one end? which end? when center drilling out for the ball what is best? a plain old hole the diameter of the ball or some kind of countersink type hole?
Thanks in advance.
 
Assuming you're doing this because you want to turn between centers with the tailstock offset, to gain the most accuracy, you should use a ball at each end of the work piece. If you only use a ball on one end, the end using the center will technically have some "bind" when offset. Also, for the best accuracy, I would center drill counter sunk holes in all pieces and then, with each piece chucked very close to the chuck jaws, re-cut the counter sinks to 60 deg. using the lathe compound. This will ensure that your counter sinks are actually centered, whereas just using a center drill does not insure that the holes are accurately centered.

Ted
 
I understand,thanks ted. What i want to do is use 8mm stainless steel ball studs, like what holds minivan trunk gas spring struts. one threaded into an mt2 taper for the tailstock and one threaded into a scrap peice of steel. If it doesnt work im only out a few bucks for a couple ball studs. if it does i know a cheap way to turn between ball centers.
 
There are special center drills for taper turning. They look like the bell of a trumpet from the side view, rather than the straight 60 degree cone shape of regular center drills. The trumpet bell shaped holes allow a regular 60 degree center to touch all around the center drilled holes they make. A regular center drilled hole does not allow a normal center to make contact all the way around the hole when turning tapers.
 
Unless you plan on forming a spherical center to be held by a ball the angle of the center is unimportant as different angles will not greatly change the contact patch, you are placing a sphere inside of a cone.

A ball will work fine however, assure that the center is deep enough that the part is not easily disloged.

I do however suggest that you use tooling balls as most are in the Rc 50-60 range as seen here. Do not choose a breakaway ball.
https://www.mcmaster.com/#tooling-balls/=15cull2
 
Ill have to post a picture bit i did get the tailstock side done. Basically just a 10mm ball attached to a 5/16-20 threaded stud. I had a spare mt2 taper i turned then bored out 5/16ths for a center drill so i just put a set screw in to hold it. My plan was to basically do the same buuuut im having trouble. I dont know whether to try and drill and tap a little scrap piece of steel and thread the ball stud into the scrap peice then just chuck it up or do like i did for the mt2 and drill out the middle and drill into the side and put a set screw in.
 
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