spindle vibration

Hi Folks,

1. I am turning a fair amount of baluster chair legs and am to the point where the skew doesn't catch (too often), but i do get a quite a bit of vibration during the roughing stage which makes it hard to plane well with the skew.

I do have a steady rest, but would like to turn without it. I am turning on a nova dvr which is pretty solid, and use a chuck, but also have a drive center with the big cross and also a center with the point and circular teeth in it. Does anyone have ideas of what could be causing the initial vibration?

2. I have lots of cherry burls from my woods and if anyone could point me to how to cut and dry them it would be helpful.

3. I have a live center with a point in the tail stock. Is there a way to put in a small cup instead of the point so that i could re turn spindles that dont have a center point?


thanks
Stevo

I can get just as good a finish with a sharp spindle roughing gouge used in a shearing fashion. I find it puts less pressure on the spindle and less bounce accordingly. Both, though, require a light touch and shallow cut to get a nice finish without introducing vibration themselves. If you are sure all the vibration is from the piece flexing under it's own momentum, then you'll likely have to use some kind of support.

Well, I turn more bowls than spindles, but have learned a few things. One is there is a ratio of about 10 to 1 for spindles, which is some thing like a 10 inch long spindle, 1 inch diameter will be fairly vibration free. So rolling pins are almost always vibration free, but chair spindles are not.

Anything beyond that will want to vibrate. If you have too much pressure on the tailstock, that will induce vibration, especially on longer thinner spindles.

Too much pressure on the bevel rub will cause vibration. This is probably the biggest problem to conquer when learning spindle turning. Same with bowl turning. "The bevel should rub the wood, but the wood should not know it." Don't know who said it, but that is a huge thing to learn for all turning. After watching Ashley Harwood turn one of her long spindles for her sea urchin ornaments, and she did finish cuts without using her finger as a steady rest, I told her, I am going to have to work on my 'dainty' skills.... It doesn't take much pressure to get a thin spindle to move and start whipping where you get those spiral marks on a spindle. Learning to go dainty will help a lot. You have to practice, a lot, especially if you can be heavy handed at times. If you are a bowl turner, that one hand push cut is an excellent exercise to practice.

robo hippy

I usually use a large skew for roughing.

I don't use a steady rest except for the "left hand steady rest", holding the skew/gouge with my right hand and using my left to eliminate vibration. For example:
Attachment 442610

I do this spindles that are thin relative to their length. Two examples of spindles turned this way, the first is a hickory handle for a shuffle hoe, the second is a couple of example spindles that taper from 1/2" to 1/8" over about 24" (one from shelving pine from Home Depot and one from walnut):

Attachment 442608 Attachment 442609

Cutting burls is sometimes more of a guess than an art or science. Sometimes the outside will suggest where to cut. Sometimes I just take a wild guess on the first cut and decide on further cuts once I see the integrity and figure of what is exposed. I cut up a fairly large cherry burl the other day which ended up being so full of rot and voids that I got just 5 or 6 useful turning squares (1.5x1.5" up to 3x3"), a box of thin pieces for a friend who does inlay, and a bunch of pen blanks to give away. If there is more "good" wood in a burl I might get larger turning squares for boxes and such or some for bowls. Some people other than me like to chuck up a burl with a lot of voids and turn some sort of bowl, hollow form, vase, etc., full of holes. Be careful.

I air dry blanks cut from burls by applying anchor seal to all sides. I weigh the blank periodically and know it's dry when the weight quits changing.

The point in the Oneway live center and clones can be knocked out from behind with a small diameter bar so you can use just the cup.

JKJ

Quote:

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Originally Posted by stevo wis

Hi Folks,

1. I am turning a fair amount of baluster chair legs and am to the point where the skew doesn't catch (too often), but i do get a quite a bit of vibration during the roughing stage which makes it hard to plane well with the skew.

I do have a steady rest, but would like to turn without it. I am turning on a nova dvr which is pretty solid, and use a chuck, but also have a drive center with the big cross and also a center with the point and circular teeth in it. Does anyone have ideas of what could be causing the initial vibration?

2. I have lots of cherry burls from my woods and if anyone could point me to how to cut and dry them it would be helpful.

3. I have a live center with a point in the tail stock. Is there a way to put in a small cup instead of the point so that i could re turn spindles that dont have a center point?


thanks
Stevo

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Two years ago, I turned a great many similar pieces all out of kiln dried sycamore. What I found amazing was that some pieces seemed to vibrate immediately, even though the pieces were all otherwise uniform. I am not sure if there was some difference in grian or ring shake or what was causing it. Most of the pieces did not vibrate until they were shaved down very thin. When they do, I found that a sharp edge and light pressure with minute shavings went best. I amazed myself on one of the pieces that the shaving was so thin and long, it looked like blonde hair hanging down from the lathe.

Personally I like starting with knocking the corners off via a bandsaw then progress with a large roughing gouge before getting to skews and other chisels. I've also seen seemingly identical pieces where one vibrates and the next one didn't. I suspect it depends on where the turning blank came out of the tree as well as how well the wood was dried in the first place. Just some thoughts.

I too, rough with a skew on smaller pieces (<3").

Another thing to check is whether you are applying too much tailstock pressure. Too much will bow skinny pieces and introduce vibration and chatter. Don't use more than it takes to hold the work. ("Skinny" is a function of length, with a 4 ft workpiece it's not hard to introduce some bow into a 1-1/2" or even 2" diameter piece, at 6" you probably only have to begin to worry under 3/4")

Quote:

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Originally Posted by roger wiegand

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Another thing to check is whether you are applying too much tailstock pressure. Too much will bow skinny pieces and introduce vibration and chatter. ...

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That's a good point. With thin spindles (perhaps 14" long, down to 1/4" or less) I've found that too much tailstock pressure can be a real problem, but too little can cause vibration too. When I I have trouble I try changing the tailstock pressure one way or the other. Sometimes cranking up the speed helps.

But when I wrote earlier I forgot the most important thing! I NEVER turn thin spindles by holding them between centers. I always hold the headstock end tightly with a chuck, a collet, or a morse taper. If the wood is held between centers, the whole thing can bow easily with the slightest tool pressure as the wood gets thin. However if one end is held tightly it in effect stiffens up/strengthens at least the first 1/3 and perhaps influences over 1/2 of the spindle. This makes a huge difference in reducing vibration!

While I do use a chuck occasionally, I generally turn a short #2 Morse taper on one end and press it firmly into the headstock spindle. This avoids the hazards of working close to a chuck and gives far better access to the headstock end. It also has the big advantage of letting me remove the piece and remount it at any time with perfect registration - nearly impossible with a chuck. (Eliminating the chuck also lets me turn longer pieces on smaller lathes.)

This picture shows some of the short #2MT ends I turn to hold the spindle. They don't need to be very long.

Attachment 442691

After turning close to the end and cutting the tailstock end loose with a skew, I generally saw off the remaining end and smooth and finish by hand.

JKJ

Folks,

thanks so much for all the suggestions.

I have lots of new things to try, especially turning the morse taper on the end; that seems to be a great idea.

A couple of things I have noticed about my chuck. When I insert a drive center in the chuck, I am getting a little runout in the point. I have to check how well it runs out without the jaws and drive and make sure everything is concentric.

Thanks again.

Quote:

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Originally Posted by stevo wis

A couple of things I have noticed about my chuck. When I insert a drive center in the chuck, I am getting a little runout in the point. I have to check how well it runs out without the jaws and drive and make sure everything is concentric.

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I think it's' best to use a drive center not held by the chuck. I must say I've never tried holding any drive center in chuck jaws but have held things by the chuck slides.

BTW, even round wood mounted in chucks is notoriously not perfectly concentric due the the variations in the way the jaws indent into the wood. This normally doesn't matter since you turn the piece concentric to the lathe, not the chuck, even if the chuck or jaws are not exactly concentric with the rotation. Of course, the problem comes when trying to remount a piece removed from the jaws.

JKJ

If you follow JKJ's advise about a chuck, and not between centers, you can try this trick. I have a Nova center, and it has replaceable points. I take the point out, and now you have a hollow center. I turn the spindle before to fit INSIDE the center, snug is good. This way the center holds the spindle with zero horizontal force. This works really well with thin finials. If you don't have a Nova or hollow center, could turn a cup that fits over your center and then turn a recess to hold the spindle in.
Another tip, use straight grained wood. If you try to use highly figured or curly wild grained wood, when you get down past 1/4", they can snap at any time, just because the grain runs across the spindle/finial...... And you're mostly done at that point. Or were mostly done, since you have to start all over.

Quote:

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Originally Posted by stevo wis

3. I have a live center with a point in the tail stock. Is there a way to put in a small cup instead of the point so that i could re turn spindles that dont have a center point?

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When I want a custom tailstock center, I use a combination of a threaded live center (see for example, https://www.pennstateind.com/store/LTCA18.html, pictured below) and a small faceplate with a block of wood attached. Put the faceplate with block of wood on the drive side of the lathe and turn it to whatever shape you need, then remove the faceplate and put it on the threaded live center and you can hold almost anything. For your spindles, you could drill a hole matching their diameter, or just turn a cone-shaped recess in the block and it will center and hold the end of your spindle. Put the driven end of the spindle in a chuck as suggested by others, and then you don't need much compression from the tailstock, just enough pressure to keep it from wobbling around.

The block of wood on the faceplate can be reshaped for new needs. If you're reusing one that's been sitting around the shop, you might want to put it back on the drive and make sure it's still symmetrical (humidity-driven wood movement can cause the block to become very slightly oblong such that it needs to be trued up). When I'm in the shop next I'll take a picture, this description might not make sense without.

Best,

Dave
Attachment 442745