Chatter Marks on Single Point Threads

[mickri]

I have been threading mostly 1018. I did have the same problem in a piece of mystery steel that may have been stainless steel. I will try doing some clean up passes at the final setting.

 

[TX COWDOC]

I've posted this in the Precision Matthews thread. Thought I'd bump this for some more visibility / help.
PM1236 single phase Baldor. Trying to thread 16TPI and getting terrible chatter / facet marks in both steel and aluminum.

This is a brand new machine.

 

[benmychree]

What sort of tools are you using, and lube?

 

[mksj]

Is this something new or what are the circumstances of it now appearing, is this a new lathe or old, do you also get chatter when turning or only threading? What technique are you using for threading? Up front it seems to be a rigidity issue or something is loose. Have you checked the gibs, tried to take passes with the gib locks on, have you checked the carriage gibs? Are you taking to deep a threading pass, is the piece held securely with the least amount of stick out. Also is your tool post slide angle set correctly?

Sometimes there can be surface finish issues related to single phase motors on lathes, but typically this would be seen in both turning and threading, and is a bit idiosyncratic as to it showing up on a particular lathe.

1340gt surface finish problem

O.K. guys, and gals, I've tried every speed/feed combo, every carbide insert I have, every HSS tool I have, I've even put vibration isolation pads between the stand and the floor...nothing seems to work. Here's what I get... Please excuse my photography skills. You can not only SEE the...

www.hobby-machinist.com

 

[TX COWDOC]

Is this something new or what are the circumstances of it now appearing, is this a new lathe or old, do you also get chatter when turning or only threading? What technique are you using for threading? Up front it seems to be a rigidity issue or something is loose. Have you checked the gibs, tried to take passes with the gib locks on, have you checked the carriage gibs? Are you taking to deep a threading pass, is the piece held securely with the least amount of stick out. Also is your tool post slide angle set correctly?

Sometimes there can be surface finish issues related to single phase motors on lathes, but typically this would be seen in both turning and threading, and is a bit idiosyncratic as to it showing up on a particular lathe.

1340gt surface finish problem

O.K. guys, and gals, I've tried every speed/feed combo, every carbide insert I have, every HSS tool I have, I've even put vibration isolation pads between the stand and the floor...nothing seems to work. Here's what I get... Please excuse my photography skills. You can not only SEE the...

www.hobby-machinist.com

Mark,
If you zoom in on the turned and faced surfaces you will see lines / patterns that are similar to those in the thread you shared. My belief is that this is showing up elsewhere but is exacerbated / more obvious in the threads. This is a new lathe. Arrived in July. Finally getting around to working with it. Pretty frustrating. I have not checked the gibs / gib locks.

 

[mksj]

Have you threaded before? Try using only the cross slide with say 0.01" per pass for first couple of passes then 0.005" then 0.001/skim pass. Lock down the tool slide. Also check the gibs, they can be set incorrectly from the factory also there are gibs on the carriage. Other things to check is the motor belt tension is should not be too tight, I think something like 1/2" midway with moderate pressure. Need to go through a sequence of ruling out the rigidity and tool post aliment issues first. You are using lay down inserts, they use a negative rake tool holder but have a positive insert, so should cut very well. I use these and get very clean threads. Like I mentioned on the single phase motor, sometime it is a problem but hard to tell until everything else is ruled out. Up front is the rigidity, something is loose or a tool height issue.

 

[TX COWDOC]

Have you threaded before? Try using only the cross slide with say 0.01" per pass for first couple of passes then 0.005" then 0.001/skim pass. Lock down the tool slide. Also check the gibs, they can be set incorrectly from the factory also there are gibs on the carriage. Other things to check is the motor belt tension is should not be too tight, I think something like 1/2" midway with moderate pressure. Need to go through a sequence of ruling out the rigidity and tool post aliment issues first. You are using lay down inserts, they use a negative rake tool holder but have a positive insert, so should cut very well. I use these and get very clean threads. Like I mentioned on the single phase motor, sometime it is a problem but hard to tell until everything else is ruled out. Up front is the rigidity, something is loose or a tool height issue.

Belts have about 1" play so not too tight / loose.