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SB 9A
Cutting a thread using the method of engaging the lead screw, running forward, stop, running in reverse without disengaging, repeat.
Running forward goes smoothly.
Running in reverse flips the belt from the pulley.
?
The spindle turns freely cw and ccw.
The lead screw grabs when I turn it in reverse by hand.
?
I removed the gear box from the lathe and all looks clean.
Any thoughts on what causes the problem in reverse?
?
How does the bearing surface on the left end of the lead screw get its lubrication?
Thanks.
?
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My SB10k has a gitts oil cap on the very left side, plus I add some oil to where the leadscrew exits the QCGB. My metric system has 2 gitts oil caps on the top.?  
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On Sep 23, 2024, at 11:25, Jack Dinan via groups.io <jack@...> wrote:
? SB 9A
Cutting a thread using the method of engaging the lead screw, running forward, stop, running in reverse without disengaging, repeat.
Running forward goes smoothly.
Running in reverse flips the belt from the pulley.
?
The spindle turns freely cw and ccw.
The lead screw grabs when I turn it in reverse by hand.
?
I removed the gear box from the lathe and all looks clean.
Any thoughts on what causes the problem in reverse?
?
How does the bearing surface on the left end of the lead screw get its lubrication?
Thanks.
?
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Just a thought here….. are you withdrawing the thread cutting tool while running the leadscrew/carriage to its start position? ?If not, the slop on the geartrain/leadscrew/half nut might be putting excessive pressure on the cutting tool. ?There, out of ideas.
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On Sep 23, 2024, at 11:25, Jack Dinan via < jack@...> wrote:
SB 9A
Cutting a thread using the method of engaging the lead screw, running forward, stop, running in reverse without disengaging, repeat.
Running forward goes smoothly.
Running in reverse flips the belt from the pulley.
?
The spindle turns freely cw and ccw.
The lead screw grabs when I turn it in reverse by hand.
?
I removed the gear box from the lathe and all looks clean.
Any thoughts on what causes the problem in reverse?
?
How does the bearing surface on the left end of the lead screw get its lubrication?
Thanks.
?
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Al:? Thank you for the suggestion. It turns out that the problem was where it usually lies ?- with me.
Instead of feeding with the half nut lever, I was feeding with the clutch knob. Several years since I cut a thread, and I just plumb forgot.
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Just a thought here….. are you withdrawing the thread cutting tool while running the leadscrew/carriage to its start position? ?If not, the slop on the geartrain/leadscrew/half nut might be putting excessive pressure on the cutting tool. ?There, out of ideas.
Cheers, ?al. On Sep 23, 2024, at 11:25, Jack Dinan via < jack@...> wrote:
SB 9A
Cutting a thread using the method of engaging the lead screw, running forward, stop, running in reverse without disengaging, repeat.
Running forward goes smoothly.
Running in reverse flips the belt from the pulley.
?
The spindle turns freely cw and ccw.
The lead screw grabs when I turn it in reverse by hand.
?
I removed the gear box from the lathe and all looks clean.
Any thoughts on what causes the problem in reverse?
?
How does the bearing surface on the left end of the lead screw get its lubrication?
Thanks.
?
|
Great Jack, you are back on the go again. ?I keep a notebook with sections for each machine in my shop. ?Each one includes info I need to know but might have forgotten…… lubrication type, setups, what not to do again, etc. etc. It’s saved my bacon more than once.
Do you have the Southbend book called “How to Run a Lathe”? ?if not, you should try to latch onto a copy. ?It’s a goldmine of everything one might need to know when running a lathe in general, and SB in particular, including setups, sharpening the cutting tools, tool heights (especially lantern style toolholders), taper turning, threading, multi-start threads, grinding, etc. etc. I still refer to mine from time to time.
Cheers,
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On Sep 27, 2024, at 14:45, Jack Dinan via < jack@...> wrote:
Al:? Thank you for the suggestion. It turns out that the problem was where it usually lies ?- with me.
Instead of feeding with the half nut lever, I was feeding with the clutch knob. Several years since I cut a thread, and I just plumb forgot.
Just a thought here….. are you withdrawing the thread cutting tool while running the leadscrew/carriage to its start position? ?If not, the slop on the geartrain/leadscrew/half nut might be putting excessive pressure on the cutting tool. ?There, out of ideas.
Cheers, ?al. On Sep 23, 2024, at 11:25, Jack Dinan via < jack@...> wrote:
SB 9A
Cutting a thread using the method of engaging the lead screw, running forward, stop, running in reverse without disengaging, repeat.
Running forward goes smoothly.
Running in reverse flips the belt from the pulley.
?
The spindle turns freely cw and ccw.
The lead screw grabs when I turn it in reverse by hand.
?
I removed the gear box from the lathe and all looks clean.
Any thoughts on what causes the problem in reverse?
?
How does the bearing surface on the left end of the lead screw get its lubrication?
Thanks.
?
|
Al: I do have that book. Agreed that it is a goldmine.
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Great Jack, you are back on the go again. ?I keep a notebook with sections for each machine in my shop. ?Each one includes info I need to know but might have forgotten…… lubrication type, setups, what not to do again, etc. etc. It’s saved my bacon more than once.
Do you have the Southbend book called “How to Run a Lathe”? ?if not, you should try to latch onto a copy. ?It’s a goldmine of everything one might need to know when running a lathe in general, and SB in particular, including setups, sharpening the cutting tools, tool heights (especially lantern style toolholders), taper turning, threading, multi-start threads, grinding, etc. etc. I still refer to mine from time to time.
Cheers,
al. On Sep 27, 2024, at 14:45, Jack Dinan via < jack@...> wrote:
Al:? Thank you for the suggestion. It turns out that the problem was where it usually lies ?- with me.
Instead of feeding with the half nut lever, I was feeding with the clutch knob. Several years since I cut a thread, and I just plumb forgot.
Just a thought here….. are you withdrawing the thread cutting tool while running the leadscrew/carriage to its start position? ?If not, the slop on the geartrain/leadscrew/half nut might be putting excessive pressure on the cutting tool. ?There, out of ideas.
Cheers, ?al. On Sep 23, 2024, at 11:25, Jack Dinan via < jack@...> wrote:
SB 9A
Cutting a thread using the method of engaging the lead screw, running forward, stop, running in reverse without disengaging, repeat.
Running forward goes smoothly.
Running in reverse flips the belt from the pulley.
?
The spindle turns freely cw and ccw.
The lead screw grabs when I turn it in reverse by hand.
?
I removed the gear box from the lathe and all looks clean.
Any thoughts on what causes the problem in reverse?
?
How does the bearing surface on the left end of the lead screw get its lubrication?
Thanks.
?
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FWIW In the files section are copies of the 3rd edition, the 56 edition and the 58 edition.?
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On Sep 27, 2024, at 5:52?PM, Jack Dinan <jack@...> wrote:
? Al: I do have that book. Agreed that it is a goldmine. _._,_._,_
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Jim B
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Jim_B