Fault / Condition |
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Probable Cause |
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Remedy |
Major diameter is under size with truncated form, but the pitch diameter is correct |
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The pre-rolling blank diameter is undersize |
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Increase the pre-rolling blank diameter in small increments until correct major is obtained |
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Major diameter is undersize with truncated form and the pitch diameter is oversize |
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Thread rolling head is not adjusted correctly to size |
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Adjust thread rolling head down this will decrease the pitch but increase the major diameter |
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Both major diameter and pitch diameter are oversize |
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Blank diameter is oversize head is adjusted oversize |
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Reduce blank diameter and readjust head, then follow setup procedure |
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The first 2 or 3 threads are rough or malformed |
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The approach rate of the thread rolling head is too fast or too slow |
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Check feed cam, programmed feed rate or hydraulic system according to type used |
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Chamfer angle is too high or not uniform |
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Check that chamfer is not more than 30 degrees to the axis and is smooth/uniform |
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The thread rolling head and component are misaligned |
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Check that the thread rolling head is on center with spindle |
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Thread slivers/flakes |
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Insufficient ductility |
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Change material/grade |
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Material is leaded for free cutting |
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If other machining parameters permit, change to a low or non leaded grade of material |
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Swarf/metal particles present in the coolant |
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Flush out and change coolant Improve filtration system |
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Over rolling thread form is full |
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Reduce blank diameter until thread form starts to truncate |
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Poor finish on thread |
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Thread rolls worn or chipped on the leads |
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Reverse rolls in the head before the leads chip. Replace badly damaged rolls |
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Component is bent or out of round |
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Blank is bent prior to rolling or bends during rolling |
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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 |