Tailstock offset taper turning?
So, let's get it out in the open, I have no formal training here. I just pick things up from other machinists. Anyway, I'm trying to turn a nice long, slow taper on a piece of .500" drill rod that is a total of 26" long. It is actually two different rates of taper with short cylindrical sections at each end.
My problem is that the work was whipping around a little, so I used my steady rest and just turned it a few inches at a time. The steady rest stopped the whipping, but also changed the angle of the work. I ended up with a faster taper than I wanted.
Is there a method of getting the steady rest right on "center" with the angle of the work? How do I determine that? Your replies will be greatly appreciated.
Need some more info.
What is the length and angle of the tapers? Is the shape of the finished part, hour glass, bell shape or stepped? Can you grip the rod in the chuck or collet at the intersection of the tapers and cut with a shorter machining run? Does your lathe have a taper attachment, (usually in inch's per foot).
I had to do that once....turn a long, thin taper. Scrap the steady rest, follow rest won't work either. I ground a hss tool bit with higher negative rake angle, took light cuts at slow feed, normal rpm. The high angle makes for a relatively deep undercut that helps prevent the work from bowing by holding it to the tool. This will work.
Thanks for the replies. The shape of the work is basically a one inch cylindrical section at .290" followed by the faster of the two tapers which is 5.25 inches long (I'd tell you the taper per inch, but my notes are in my shop across town), then the second, slower, taper is 15.75 inches, followed by a cylidrical section of 4" at .468".
The work is a mandrel for drawing down brass tubing to a taper for musical instruments. My old method of making them was to cut the rod down in steps in 1/2" increments, then file the steps down to a smooth taper. That only took about four days and wasn't exactly accurate. I don't have a taper attatchment BTW. I don't have any collets either.
So I should really scrap the steady rest? What angle do you suggest for the cutter?
Stuart, I would suggest a tool post grinder with maybe a 60 grit and a medium grade (hardness) such as an "I" or "J" for ease of friability. Just make sure, if you grind it, that you allow it to spark out on the last couple of passes of a couple of ten/thou each to keep down the possibility of shaft deflection.
[This message has been edited by jim (edited 10-08-2002).]
Soemthing that long and skinny, I'd just spring it with the steady leaving a full diameter section for a strady journal. Onece the taper (actually a flare) is cut move the steady and cut down the steady journal.
What your making is a mandrel, probably the lead pipe for a trumpet.
Hey Jim. I was wondering about grinding it. That would get me closer to the surface finish I want, but I'm kinda low on funds at the moment, so I won't be buying anymore tooling.
Hey Forrest. Actually, the mandrels (I've got several planned if I can get this to work) are going to be for the leadpipe and first branch of a Horn. Are you a Brass man? Anyway, I didn't understand a thing you said. I caught the gist of using the steady rest. How do I make sure it is turning true and at the correct angle?
I got to thinking that if I just indicated the rod at several points I can make sure its running true, even though it's at an angle, right? Then I can just make all my adjustments to the steady rest. I also got to thinking that this method will take more than the time it will take me to cut the part. Any better ideas?
Hey bdarin, I'm still going to try your tool bit method, I just have to find all of my @#$%&*! tool bits. I'll let you know how that turned out. Thanks again.