Axial Problem Solving

Fault / Condition

 

Probable Cause

 

Remedy

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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