cutting shafts for threading

[benmychree]

Normally, the die should "top" the thead; although filing the top is normal proceedure , especially with threads that are single point threaded in the lathe. Cutting threads in the lathe with button dies seldom results in a thread that is co axial with the axis of the part, very generally it will wobble. It is poor practice to thread in the lathe in this manner; at the very least, one can rough out the thread with a single point tool and finish with the die. I have always had availabe, die heads, such as Geometric or Hartness or J&L tangent dies for this sort of work; they cut an accurate thread without wobble or significant lead error that button dies create.

 

[markknx]

Normally, the die should "top" the thead; although filing the top is normal proceedure , especially with threads that are single point threaded in the lathe. Cutting threads in the lathe with button dies seldom results in a thread that is co axial with the axis of the part, very generally it will wobble. It is poor practice to thread in the lathe in this manner; at the very least, one can rough out the thread with a single point tool and finish with the die. I have always had availabe, die heads, such as Geometric or Hartness or J&L tangent dies for this sort of work; they cut an accurate thread without wobble or significant lead error that button dies create.

Is there a explanation for this? I have had this problem, Thought it was me. have had other times when I took great care and had no issue. Would seem the part being on center an the tailstock being on center that it should thread on center. But sometimes things are not that simple. Could it be button dies are not centered?