Lathe - Barber Shop Pole Pattern, Loose Carraige?

I just realized you have a Grizzly G4003 lathe.

Check the fit of the chuck to the D1-4 register on the spindle nose of the lathe. See if you can get any feelers between the flanges. There should be no space between the faces. If you confirm this being ok, next will be pulling the spindle and changing out the spindle bearings.

You may also go to Grizzly's website and look through the comments made and see if anything surfaces. Call them, they may already know the fix.
 
Coolidge,
I agree with Chips&more. It is a harmonic issue. Caused by motor, gears, bearings. You need to find the frequency. Back in the 90s we used a frequency meter to find harmonic vibrations in cars and trucks. As I recall you would get the harmonic frequency at the worst spot in the vehicle (your second was crawling around placing the meter in different places to find the closest source). You would then do some math on different things like gears ratios to determine tire rotation speed, driveshaft speed, different moving components. Once you knew the frequency it was a simple matter to determine what the source was.
Something like this doesn't have enough range http://www.ebay.com/itm/Vintage-Fra...424?pt=LH_DefaultDomain_0&hash=item4aed932540
This seems a little overkill http://www.ebay.com/itm/Fluke-805-V...719?pt=LH_DefaultDomain_0&hash=item4aed2b7387

Is there an app for the more capable phones maybe?

If it were a chuck balance issue I would expect it to mark in the same spot all the time drawing straight lines. If it was a bearing I would expect it to move around more as the rollers shift. The fact that it pulls off really cool patterns makes me think it is something that is constant movement varied by gearing/drive ratio causing the pattern to move uniformly. There may be a point (speed) where it vanishes all together.

How does the machine sound?

Dave
 
Flapping belts will do it for sure. On my old Clausing it produced beautiful work until the day it didn't. One of the two matched belts decided to loose its shape, literally. Took the belt off and it would not lie flat on its side, it was warped. Put two new matched belts on and viola. You can get matched belts at Napa auto parts stores, usually takes a few days but they got them in catalog. Way cheaper at Napa than most other places. The high end matched belts at Napa are made by Gates.

michael
 
Dave the lathe sounds fine, the spindle seems tight and smooth. I re-adjusted the spindle bearing pre-load and I think the spindle bearings are fine, keep in mind they are upgraded NSK bearings. It spun really free and smooth as I approached zero end play, the final 1/16 turn of pre-load after eliminating the end play did exactly what I expected, my dial indicator showed zero movement and I could feel the pre-load in the spindle then. I guess I would describe it as slightly more difficult to turn the spindle but still very smooth and free. I had snugged up the pre-load even further before, this had no effect on the spiral pattern at all.

The only thing that has changed the spiral pattern has been the amount of belt tension. On the G4003G there is a separate drive shaft the motor connects to via the belts, e.g. the belts don't connect directly to the spindle, they spin this drive shaft which in turns spins the spindle via gears in the head stock.

So too little belt tension and I get the spiral pattern. Too much belt tension and I get a different spiral pattern and a bearing doesn't sound very happy. With just the right amount of belt tension the spiral pattern mostly goes away. Its not the belts, I have tried both the link belts I had on the lathe and the Made in USA variable cogged NAPA rubber V belts. I tried both 2 belts and single belts of both types just to eliminate any harmonics that two belts might be producing at a resonance. None of this had effect on the spiral pattern.

Now that my annoyance meter as dropped from 10 to 9.7 I will troubleshoot this a bit more this evening.
 
Only need a very small flaw on a roller/cup/cone to cause some serious harmonics, been there, done that, changed bearings, Presto... sorted.
 
Although my issue happened to be spindle bearings that sat idle for a time, it could happen to any roller bearings. Check 'em all, may not be able to "feel" it when rotating bearings by hand(my spindle bearings didn't show anything on dial indicator, rolling by hand and assembled dry for testing. Light mark on one cup, when reassembled properly, with grease as per original or oil as per my modification, i had absolutely horrendous harmonics only when turning load applied).
 
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Coolidge,
I have the same lathe. The last picture is interesting how the light repeats the pattern so exact. I see you are turning on B2 or B3 for your two rpms. What about A1 or C1? Get off the "B" gear for a test. What diameter is your piece? I'll see if I can try it tomorrow on mine with your speeds. What is the gearbox set at?
Dave
 
Is it practical to send the motor/drive shaft assembly out for balancing? That is exactly the type of sound you get in a twin engine aircraft or boat when the engines are running just a few RPM difference.
 
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