I think your problem comes from lack of rigidity. basically your tool is bouncing off the work peice.
1. check your spindle bearings and make sure they are tight. (my 9x20 was loose from the factory.) you want the head to be really warm to the touch when running about 1000 RPM. you may want to pull the spindle out and lube the bearings prior to this.
2. i found the my compound was flexing. buy a quick change tool post with a larger diameter shank down the center. the stock one i think is around 8 mm. i currently use a 13 mm post down the center of my quick change tool post.
3. add a larger diameter handwheel to the cross slide feed. you can replace the lead screw as well but i noticed the largest difference with the larger hand wheel and tightening the gibs.
4. get some carbide tooling. do not get the brazed carbide get the inserts. there are inserts specially designed for aluminum and they are well worth the money.
5. after the mods above i can take .150 per pass when turning. thats about .300 of mterial removed from the diameter. (i did upgrade to a 3hp motor and a vfd for my lathe.)  |