Acceptable vibration?

[John Kananis]

Is there such a thing? I've noticed some on my laguna 18/36. If I play with speeds, I can almost eliminate it but not completely. This is on a doug fir spindle, approx 4 inches in diameter and maybe 12 or 14 inches long. (After the spindle has been trued)

I put a dual indicator on the drive side and I'm getting .002 runout both inside the Morse taper and behind the threads. With no heat buildup in the headstock. I suppose that I'm just not experienced enough to know what normal is - thanks for the help.

[Edward Weber]

Just so I'm clear, there is vibration with the DF blank mounted.
This is not surprising, wood is not a homogeneous material. Density/weight and moisture content vary throughout the wood.
If you're having the vibration with nothing mounted I might be concerned.

[John Keeton]

Ed is right. An out of balance spindle will create a harmonic reaction and actually intensify the vibration. When you find the magic speed you are counteracting the harmonic vibration. What you describe is common - particularly with wood that isn’t fully dry.

[Kevin Jenness]

Are you measuring runout with the late running? If so that seems a bit hard on the indicator tip. If there is .002" runout turning by hand that is a bit high (though not outrageous) and could be contributing to vibration.

[John Kananis]

Thank you, gentlemen - was kind of concerned. Yes, the lathe runs well without the spindle mounted.

I guess this will be much worse when I mount a large bowl blank.

Is the amount of runout I mention (.002) acceptable?

[John Kananis]

Both by hand and on at slow(est) speed. Is there any way to correct it?

Are you measuring runout with the late running? If so that seems a bit hard on the indicator tip. If there is .002" runout turning by hand that is a bit high (though not outrageous) and could be contributing to vibration.

[Bill Howatt]

A green bowl blank can literally cause an unbolted lathe to jump around the shop at various speeds. IMO, 0.002" at the spindle is high by something like 4X but it isn't as critical on a wood lathe as it would be on a metal lathe. Problem is to determine what the problem is. First thing is to make sure the surface you are measuring is totally clean. Possible causes are bearing problems or a slightly bent spindle.
The responses mentioning wood not being a homogeneous material are absolutely correct but I'm a bit surprised you couldn't tune it out on a spindle that size by speed adjustment (it is a variable-speed lathe, isn't it?).

[mike calabrese]

What you describe is common however you may have a quick improvement opportunity.
With rotating machines there is a common fault called soft foot. This is a condition when typically one or more of the machine feet are not loaded, supporting an equal amount of weight to the floor or a mounting surface. There is an easy check, operate your lathe at the lowest speed where the vibration is evident. With the lathe running go under the lathe and place a finger so you are touching the mounting foot and the floor at the same time. What you are looking for is a bouncing feeling between the foot and the floor which suggests that foot is light on contact with the floor. Try very small amounts of adjustment say lowering the foot to add more load to, against the floor.
This can be a little frustrating as you may find you are chasing "the bounce" around the feet .
the condition, vibration swings at different speeds is always common especially if the floor is somewhat soft like a wood floor as opposed to a concrete floor mounting that is less likely to vibrate from the excitement of the machine. A more common situation is with a car where a wheel is a little out of balance at certain speeds it is felt while at others it is not perceptible. Harmonic vibration is common as stated by posters above . Good luck
calabrese55

[Reed Gray]

For spindle turning, there is a 10 to 1 ratio. 10 inches long and 1 inch in diameter, you will get almost no vibration/run out in your spindle. If you go thinner than that, then you will get vibration. Not sure if that is the case here or not. This can vary a bit with the wood, and how much pressure there is on the tailstock end. Too much pressure will make the spindle flex.

robo hippy

[Richard Coers]

.002" is just a red hair off perfect. We aren't making parts for space craft!

[John Kananis]

I just wanted to say thank you to all those who replied. The feet are solidly planted btw, it was the spindle I was working on.

[Reed Gray]

How long is the spindle? What is the diameter?

robo hippy

[John Kananis]

It was 4 inches in diameter and about 14 inches long. It was definitely the stock. I've mounted some others since with no issues.

My only real concern is what happens when I start mounting larger off-balance bowl blanks?

How long is the spindle? What is the diameter?

robo hippy

[Bill Howatt]

As I tried to point out above, when you mount a large off-balance bowl blank the lathe, unless it's bolted down, can jump all over the shop. Your 2 thou won't matter a darn.

The solution is to turn the speed down to stop the vibration and this is the beauty of a lathe that has a speed range below roughly 400 RPM especially when combined with variable speed. A lot of the older lathes really were designed for spindle turning and their lowest speed of say, 5-600 RPM made them less than ideal for bowl turning.
Of course, you can try to trim your blank to round as much as possible before you mount it.

Once you start to turn, the more you true it up the smoother it will run and you can increase the speed to just below annoying vibration speed.

[John Kananis]

Thanks Bill. Being newer at this keeps me on my toes and I'm on my own with this (I know enough woodworkers but no turners) so I just want to make sure I'm getting it right. Appreciate your input.