old lathe question

Hi out there in the www.

I have an older lathe that chatters and sort of vibrates when cutting certan cuts? being new at lathing, sugestions as to what i am doing wrong would be helpful

Thanks

Mars

what type of material, size of material and how far is it sticking out of the chuck? What tooling are you using?

Mars;

If you are doing this for a hobby, you are welcome to visit my shop on a weekend to get some pointers. I'm here most weekends but call first. Contact info and map are available at www.metronorth.ca For competitive and confidentiality reasons I can't extend the same offer if you are doing this professionally, I hope you understand.

Glenn @ Metro North.

Mars,
Post a picture of your lathe. Some of the guys here know these machines inside and out. The things you learn when setting up and cutting become inherently obvious after awhile.
Generally the watchword is "ridgidity". Just before you start a cut, stand back and look at the tool set-up. What you are looking for is a straight line of force down from the point of the tool to the bed ways. If your tool set-up diverts the path of force too much, you will introduce the risk of chatter. Additionally, the hardness of the material being cut can cause chatter. The ridgidity of the material being cut is also a consideration. A two-inch diameter bar of steel is a lot less likely to chatter than a one-inch piece.

There are things you can do to help preclude the risk of chatter as you set up your tooling. One is to adjust the gibs on your cross-slide and tool post slides to eliminate as much slop as is reasonable. I.E. you don't want to work too hard turning the cranks on both, plus it prematurely wears out the lead screws.

Some of the old lathes were equipped with the Armstrong tool holders for high speed steel. These are ok, but are not as ridgid as some of the newer tool holding rigs. I. E. the Aloris style tool holding system.

The sharpness of your tool and the angle the cutting edge presents to the material being cut can introduce the risk of chatter and other vibration. Generally, you want the chip to slide away from the tool as the cut is made, otherwise the tool bit will heat and fuse cut material to the cutting edge and leave a poor finish on your work.

If you could find a hands-on machinist class somewhere locally as well as taking advantage of Glenn's offer, you will be generating chips without serious problems before you know it.

Finally, verify that your machine is level and each point of contact with the floor is carrying its alotted load. I.E. if one or more of the leveling adjustments is loose or not set correctly, your lathe will sing like a banshee. WWQ

Hi Mars,
in addition to Bills good advice. I would check that your tool is at centre height( trap a 6" rule between the tool point and the work, the rule should be vertical). Try using a bungee cord to pull the cross slide back away from the work, it'll help soak up any slack in the feed screw thread.
Frank

How are you holding the work,3 jaw, 4 jaw chuck or collets?
How long is the work extending out from the chuck? What make and model of lathe do you have?
Can you supply some pic's?
What type of cutting is giving you the problem, turning or facing, threading, boring?

Hey Thanks for all of the advice... I am trying out some of the sugestions, the main chatter problem started when i was turning a 6.25" diameter roller, at 30" long.

also does anyone know what kind of lathe this is (see photos) the name plate says Sebastian, but i think it is something diffrent.

Thank you

Mars

Heres a link to his photos..

http://www.geocities.com/workpress/Lathe.htm

Looking at the photos didn't tell me much about what might be wrong. Looks like the tip of your live center is pretty worn, plus the tailstock seems extended more than I would want it.

Looks like you're gripping the part in the chuck by the inside diameter?

I can't be sure but it looks like your cutting tool would be about a 1/4 inch below centerline? Check it against the tip of your live center to see. Also bring the tool holder in a bit closer to the latern tool post if possible.

What material is this roller made of? Aluminium, brass, plastic, steel?

Very interesting machine to say the least. It has a thread chase dial but no gearbox, dials on the cross slide but not on the compound. Is the base of the compound home made? Looks like it should have been longer.

The lathe appears to be an early Sebastian like one of these;

http://www.lathes.co.uk/sebastian/index.html

It is a change gear machine, and will have no QC gearbox. The compound is possibly grafted on from another lathe, or is a later version than the one on Tony's site.

Power feed appears to be a belt drive, which some machines used.

The machine is capable of the work without chatter, but we will need more information, material, speeds & feeds to begin with. A photo of the actual setup would help.

With the age and condition of the machine, wear to the headstock bearings is also a possible source of the problem.

More great advice and i was cutting under the center of the metal, when i adjusted that using a ruler i was cutting steel smooooothly.


Thanks for all the good advice

Mars