I am getting this pattern on a piece I'm machining on the lathe. Have seen it on this machine before but never tracked it down. Workpiece is way out of balance so only turning at 150 RPM. 1-1/4" diameter. 0.010 depth of cut. I am using an 8" long, 1" square tool holder with hss tool. I don't think the extreme stickout is the main issue as I've seen similar patterns when using minimal stickout. Lathe is a summit 20x80, 4000 lbs so not a weight issue either. I can not move the chuck vertically at all with a 5' bar. Anybody have a suggestion?
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Lathe chatter/pattern
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Lathe chatter/pattern
I am getting this pattern on a piece I'm machining on the lathe. Have seen it on this machine before but never tracked it down. Workpiece is way out of balance so only turning at 150 RPM. 1-1/4" diameter. 0.010 depth of cut. I am using an 8" long, 1" square tool holder with hss tool. I don't think the extreme stickout is the main issue as I've seen similar patterns when using minimal stickout. Lathe is a summit 20x80, 4000 lbs so not a weight issue either. I can not move the chuck vertically at all with a 5' bar. Anybody have a suggestion?You may only view thumbnails in this gallery. This gallery has 1 photos.1 PhotoTags: None
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First rule.................... fix what you know is wrong.
The extreme stickout is clearly not helping. Change that first, see if it changes anything. Same for the work, support it with T/S or a steady if it sticks out too far
Change speed.... if the machine is single phase, that may not do anything, but if 3 phase, it ought to make a change.
Change feed and/or DOC.
Check the carriage for "rocking horse motion", tipping back and forth, usually corner to corner, but sometimes left and right as you look at it. Another test is to reverse feed without changing the cut. If it then cuts more, it may be shifting/twisting relative to the ways and have the "rocking horse" problem.
Look for swarf under the toolpost, loose toolpost, loose compound, etc.CNC machines only go through the motions
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Is your location north or south of the equator?
Mercury is in Scorpio, (this always causes chatter) at the moment, it enters Sagittarius on 12/1/2020 as seen in the northern hemisphere.
The chatter problems should be over by December 5th in the north and a few days later in the south.
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Originally posted by boslab View PostMotor problem?, belt bearing or mains, very regular pattern for chatter,
mark
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That works out to 49 FPM, which may be too slow for good results. It might also be torque ripple, especially if it has a single phase motor, or it could be a wonky gear tooth in the power train. Does lube help?http://pauleschoen.com/pix/PM08_P76_P54.png
Paul , P S Technology, Inc. and MrTibbs
USA Maryland 21030
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Originally posted by PStechPaul View PostThat works out to 49 FPM, which may be too slow for good results. It might also be torque ripple, especially if it has a single phase motor, . . .
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Originally posted by genea View Post
When I've experienced chatter ( I'm tempted to say every single time, but maybe I'm forgetting something ) I've managed to eliminate it without changing from a single phase to a three phase motor.
Somehow methinks that if a 20x80 lathe can't take 10 thou without chattering, a major issue is afoot, either with the machine or setup.
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I tried several suggestions from this thread. Nothing made much difference until I took 1 of the 2 belts off. Finish is pretty good with dcmt insert now at 220 rpm. It seems that 1 belt is slightly longer than the other. See attached photo for setup. The shaft I am trying to repair is offset from center on the disc. The disc is almost touching the tool post in the pic, can’t get in with a shorter tool.You may only view thumbnails in this gallery. This gallery has 1 photos.1 Photo
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Have you changed the belts?, ( I must admit I had a problem recently due to a motor bearing on mine, lumpy running I suppose) and yes as MB points out it doesn’t have to be motor etc, but after a few decades messing things up it either loose blunt or shaking, my go to list I suppose, ( I cringe at some of the tool /work overhangs or stick outs I see on the utube, that’s definately looking to get the things resonating)
the lathe should be able to take most people well past where they feel comfortable!
mark
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No I haven’t changed the belts, just took one off. I am using the minimum stick out I can in this case. It’s a one inch square bar and 0.010 depth of cut. I don’t believe the stick out to the main issue. Originally a 10hp 3 phase machine it is currently running a 5hp single phase baldor motor. It is fine on lower speeds but doesn’t have the power to get rolling at max 1500 rpm
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