Troubleshooting Threading Problems and Solutions

Following are some of the more common Threading Problems that can occur. If you need further assistance, please call us at
585.429.5000, or use the Contact Page to email a description of your problem. For detailed specification on particular Thread Roll Attachments, that information is available online in the Thread Roll Attachments Page. You can also download or Thread Rolling Solutions PDF to help determine correct working face and roll position.

Situation	Problem	Solution
Slivers or flakes on threads	1. Rolls not in match	1. Resynchronize rolls
	2. Center line of rolls not parallel with center line of work	2. Check slide for alignment
	3. Loose or worn cross slide or adapter	3. Check slide gib and springs. Tighten adapter if used.
	4. Overfilling rolls	4. Reduce blank diameter
	5. Material not adaptable to cold-working	5. Change material. Check with material supplier.
	6. Rough finish on blank	6. Regrind tooling
	7. Seamy stock	7. Not suitable for roll threading
	8. Feed rate too slow, causing rolls to slip on work	8. Increase rate of penetration
	9. Incorrect roll diameter	9. Use correct rolls for job

Situation	Problem	Solution
Drunken Threads	1. Rolls not in match	1. Resynchronize rolls
	2. Center line of rolls not parallel with center line of work	2. Check slide for alignment
	3. Inaccurate rolls	3. Replace rolls
	4. Work bending during rolling.	4. Support part during rolling operation or slow down penetration rate if possible

Off-Size Threads	Problem	Solution
Pitch Diameter and major diameter, both oversize	1. Oversize blanks	1. Reduce blank diameter
Pitch diameter oversize, major diameter correct	2. Oversize blanks. If finished thread is full, thread on roll is too shallow.	2. Use correct rolls for job
Pitch diameter oversize, major diameter undersize	3. Insufficient penetration on rolls. If finished thread is full, thread on roll is too shallow.	3. Increase roll penetration
Pitch diameter correct, major diameter oversize	4. Blank too large. Thread on roll deeper than necessary.	4. Reduce blank diameter
Pitch diameter correct size, major diameter undersize	5. Blank too small. If finished thread is full, thread on roll is too shallow.	5. Increase blank diameter. Use correct rolls for job
Pitch diameter undersize, major diameter oversize	6. Excessive penetration. Thread on roll deeper than necessary.	6. Reduce roll penetration. Use correct rolls for job.
Pitch diameter undersize, major diameter correct size	7. Blank too small. Thread on roll deeper than necessary.	7. Increase blank diameter. Use correct rolls for job.
Pitch diameter and major diameter both undersize	8. Blank too small	8. Increase blank diameter

Situation	Problem	Solution
Out-of-round thread	1. Out of round blank	1. Shave tool not reaching center or not cleaning up rough form diameter
	2. Center line of rolls not parallel with center line of work	2. Check slide for alignment
	3. Feed rate too high	3. Reduce rate of penetration
	4. Insufficient work revolutions	4. Reduce rate of penetration
	5. Material not ductile enough for cold-working	5. Change material. Check with supplier.
	6. Attachment not on center line of work	6. Reset cross slide with gauge

Tapered Threads	Problem	Solution
Pitch diameter straight. Major diameter tapered and not filled on small end	1. Tapered blank	1. Straighten blank
Pitch diameter and major diameter both tapered same way	2. Tapered blank	2. Straighten blank
Pitch diameter and major diameter tapered in opposite directions and thread not filled out on end with small major diameter	3. Rolls not penetrating deep enough on edge with large pitch diameter and small major diameter, or work bending during rolling	3. Support part during rolling. Part deflecting out of contact with center of rolls.
Thread with expanded lead	1. Expanded lead in rolls	1. Use correct rolls
Thread with expanded lead	2. Material extruding on short length of blank	2. Use longer blank and remove excess in another position
Thread with contracted lead	Contracted lead in rolls	Use correct rolls for job
Poor thread form	1. Work bending during rolling	1. Support part during rolling
	2. Rolls not in match	2. Resynchronize rolls
	3. Too many work revolutions	3. Increase rate of roll penetration
	4. Center line of rolls not parallel with center line of work	4. Check slide for alignment
Thread filled out in center, but not towards ends, or vice versa	1. Blank with varying diameter from end to end	1. Check blank for taper or shave tool not reaching center
	2. Center line of rolls not parallel with center line of work	2. Check slide for alignment
Poor finish on thread	1. Overfilling rolls	1. Check blank diameter oversize.
	2. Rolls not synchronized.	2. Resynchronize thread rolls.
	3. Material accumulated in threads on roll.	3. Replace rolls if material cannot be removed.
	4. Material not ductile enough for cold-working.	4. Change material.
	5. Chips, from other operations, between rolls and work.	5. Make sure a good jet of clean oil is reaching rolling position.
	6. Correspondingly poor finish on rolls.	6. Replace rolls.
	7. Rolls that are work or broken	7. Replace rolls

Situation	Problem	Solution
Split thread-axially	1. Seamy stock	1. Change stock
Split thread-axially	2. Mark from shave tool or hollow mill	2. Regrind tooling

Situation	Problem	Solution
Crests not filled out	1. Blank too small	1. Increase blank diameter
Crests not filled out	2. Thread on roll too deep	2. Replace rolls with rolls of correct depth for job. NOTE: Special truncated rolls are available from Winter.

(Many users do not consider the above situation with serious objection, and by allowing their threads to pass with crests not filled out, overloading of rolls is avoided and roll life is prolonged.)

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Situation	Problem	Solution
Scuffed crests	1. Attachment not retracting fast enough	1. Increase speed of roll retraction
	2. Rolls and gear train building	2. Check gear train, remove any foreign matter
	3. Rolling not on center line of work	3. Reset slide with gauge
	4. Material accumulated in threads on rolls	4. Check oil jet flowing on rolling position
	5. Insufficient wall thickness	5. Machine hole later in operation or use smaller drill
	6. Improper supporting mandrel	6. Use proper supporting mandrel
	7. Feed rate too high, causing too rapid penetration	7. Slow down penetration rate

Situation	Problem	Solution
Hollow work, hole enlarged	1. Material extruding due to insufficient wall thickness.	1. Use smaller drill before rolling
	2. Supporting mandrel too tight	2. Reduce mandrel diameter
	3. Blank too large on major diameter	3. Reduce blank diameter
	4. Feed rate too high causing too rapid penetration.	4. Slow down rate of penetration

Situation	Problem	Solution
Hollow work, out of round	1. Material deforming due to insufficient wall thickness.	1. Drill later in cycle.
	2. Feed rate too high causing too rapid penetration.	2. Slow down rate of penetration.
	3. Too few work revolutions.	3. Slow down rate of penetration.

Situation	Problem	Solution
Hollow work, tapered threads	1. Uneven and insufficient wall thickness.	1. Drill later in cycle.
	2. Improper mandrel not giving support where needed.	2. Check mandrel for size with hole.
	3. Feed rate too high causing too rapid penetration.	3. Slow down rate of penetration.
	4. Taper of rolls not great enough to compensate for tendency of work to taper.	4. Use correct rolls for job.