Axial Problem Solving

Fault / Condition


Probable Cause



Major diameter is under size with truncated form, but the pitch diameter is correct


The pre-rolling blank diameter is undersize


Increase the pre-rolling blank diameter in small increments until correct major is obtained

Major diameter is undersize with truncated form and the pitch diameter is oversize


Thread rolling head is not adjusted correctly to size


Adjust thread rolling head down this will decrease the pitch but increase the major diameter

Both major diameter and pitch diameter are oversize


Blank diameter is oversize head is adjusted oversize


Reduce blank diameter and readjust head, then follow setup procedure

The first 2 or 3 threads are rough or malformed


The approach rate of the thread rolling head is too fast or too slow


Check feed cam, programmed feed rate or hydraulic system according to type used


Chamfer angle is too high or not uniform


Check that chamfer is not more than 30 degrees to the axis and is smooth/uniform


The thread rolling head and component are misaligned


Check that the thread rolling head is on center with spindle

Thread slivers/flakes


Insufficient ductility


Change material/grade


Material is leaded for free cutting


If other machining parameters permit, change to a low or non leaded grade of material


Swarf/metal particles present in the coolant


Flush out and change coolant Improve filtration system


Over rolling thread form is full


Reduce blank diameter until thread form starts to truncate

Poor finish on thread


Thread rolls worn or chipped on the leads


Reverse rolls in the head before the leads chip. Replace badly damaged rolls

Component is bent or out of round


Blank is bent prior to rolling or bends during rolling


Material has inherent stress anneal material

Blank is not perfectly round

Check pre-turning operation particularly on long threads

Thread rolling head and component are misaligned

Check that the thread rolling head is on center with spindle

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