Strange patterns when turning

[dobbslc]

I've been using my lathe a few times in the last couple of days and noticed that when I'm tuning a piece of 1" mild steel with the carriage under power it leaves a rippled finish along the part that I can feel with my finger!
If I try turning it by hand it's coming out ok.
Could the carriage lead screw drive have a bind in it causing the problem?
It seems I get one thing sorted on this lathe then something else crops up.
Any suggestions?
Thanks

 

[ronan]

Chatter, the workpiece, the cutting tool, or machine is vibrating. This can be remedied by changing your feeds and speeds.

 

[BrokenBiker]

if power feed is faster than hand feed, turn feed rate down and try again on powerfeed...or turn spindle speed up...feeds and speeds are important for a good finish

 

[BrokenBiker]

depending on the length of the job you may also need a tail stock centre to support the end of the bar too

 

[ronan]

When i get chatter or rough surface finish, i always slow things down, the feed rate and spindle speed, but have found that sometimes with carbide tipped tools, that they like a heavy cut.

 

[BrokenBiker]

When i get chatter or rough surface finish, i always slow things down, the feed rate and spindle speed, but have found that sometimes with carbide tipped tools, that they like a heavy cut.

i find with carbide tools that you need a specific tool for light cuts, most of them do like heavy cuts etc but i found that with my little chester if i was getting chatter turning the spindle speed up a bit and the feed rate down a bit sorted it

 

[ronan]

Yup its whatever works bb, so many variables, including the rigidity of the machine itself, some of the cheaper chinese machines can't be as stable as the old british, european and german machines where everything was made of generous amounts of cast iron.

 

[dobbslc]

Thanks for the replies. It's definitely not chatter, it's cutting with a nice sound and smoothly. It's like something in the drive is causing the problem as it cuts fine when moved by hand.
The part is only about 1 1/2" from the Chuck and I've tried various speeds and feeds, upping the speed did help a bit and slowing the feed more so, I also loosened the carriage gib a bit as it seemed a bit tight and that helped too.
I've also tried different tools ( carbide and hss ) the hss needs a sharpen though but not much difference to be honest.
I'm going to strip the lead screw down and check for any binds and also make a bronze bush to replace a tight crap plastic one on one of the drive gears.
It's a Chester lathe so it's ok but no Harrison.....

 

[Screwdriver]

Stop the machine at the point you are experiencing that anomaly and check for backlash in the feed screw. Might be a good idea to have a close visual inspection of the lead screw too. I would probably grab hold of the apron and see how it feels under power but thats fantastically dangerous of course.

S.

 

[ronan]

Is it a square acme type screw that is used to power the feed ?