Chatter marks???

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Bubba57

Bubba57

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Joined
Mar 11, 2014
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103
Location
Lake City, Florida
I've only been turning a short time (5 months) so I'm unsure if this is what I'm suffering from and also how to remedy them. I'm getting a series of small rhythmic 'gouges' in my turnings. It doesn't seem to matter if I use HSS or the magic carbide tools. I've tried sanding the tool rest in hopes that making it smoother will help but have had little luck. Sanding them out doesn't seem to work, either. I use the standard 5 roll, 150 - 600, system and thought that the first few grits would eliminate them.....NOT! Trouble is...I can't feel them or see them until I apply the finish and then....BAM...in my face. Any ideas?
 
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A picture would sure help. Most turning vibration induced problems are caused by too much tool pressure or too aggressive of a cut. Once you get the spiral started, the tool will often ride on them, and even make them worse. Relax your hands, take lighter cuts, and let the tool do the cutting. Don't force it! Maybe drop to 120 grit, or add a backing block behind the sandpaper so it won't conform around the spiral.
 
It is amazing how many small, really fine chatter marks and sanding scratches show up as the pen is made smoother and smoother. My advice so far (and I am still relatively new also, about 12 months - 1 year), keep everything really sharp (!), watch your techniques so that you do not make any mistakes, and be really careful as you finish.
 
Lathe speed is the first guess (I agree a picture would help).

Tighten the tailstock is the second guess (vibration is minimized)

You ARE using a mandrel???

The more clues, the more we can make the guesses better!!
 
I'm using a mandrel with a mandrel saver in the tailstock. I usually keep my tools pretty sharp and this has happened even with a fresh carbide tip. The tool rest is usually within a half inch of the workpiece. Normally, once I start shaping the pen, rpms are 12-15 hundred. Is that fast enough? Too fast? What's the rest of the world turning pens at? The backer block sounds like it could help. Another clue that might help is that I'm only seeing the problem in the center of the blanks. The 3/8 - 1/2 inch at the nib, cap, and center band seem to be fine.
Thanks for tips...I'll keep plugging away.
The chatter marks DO have a rather pleasing pattern to them...if all else fails I guess I could fill them with a contrasting color! :wink:

If ya can't hide it.....paint it red!!!
 
Chatter is vibration caused from either the cutter or the material itself, more often than not it's the material you are cutting. Some are more prone to harmonic changes than others.

Shortening the distance from the cutting area to the headstock will reduce or remove the problem without touching the rpm's. changing the rpm's is also good but that will more often than not change the frequency of the chatter. As previously noted dull tools imposes additional changes in the material which also feeds the beast. Not always the best choice to change the rpm's.

problems such as out of round, over pressure, thickness, type of material and open ended (no tail stock) increases the vibrations. One other interesting sources of vibrations entering the lathe from external sources, i.e. machinery, music/speakers and the like.


Also keep in mind to that ALL turning invokes vibration. Most of the time it is not noticed but any slow motion macro capture will very quickly point that out.
 
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Another thought: If you are using the mandrel to do TWO blanks at a time, it is long enough to have chatter in the middle, while the ends are more stable.

Eliminate this problem by turning one blank at a time, thus making the distance from headstock to tail live center point (or mandrel saver tip) only about 4". Should eliminate all vibration.
 
I had the same kind of problem with that too but there was a tad much play on the mandrel and I found that if I put a few washers on one end next to the bushing and it work well for me. On my first pen I had trouble with the little chatter marks and I too could not feel or see them until the finish was put on... Grrr... But that was my first pen. I think the washers helped my problem. Good luck with yours... Fay
 
Maybe I missed it but if the blank gets hot it goes out of round and will cause chatter as well. Stop from time to time and let the blank cool. Especially with acrylic blanks and some woods do this. Too much pressure on the blank causes heat, again let the blank cool from time to time. Yes the shorter the mandrel the better as stated above.
 
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