I turn mostly hollow form vessels, but today I was turning a balustrade for a friend. The billet was 33 inches long and 1 1/2 square. There was a fair amount of vibration, which I tried to counteract by wrapping my left hand around the back of turning and with my left hand thumb applying some pressure on the tool as I cut. The vibration was reduced but not eliminated. When I used to watch videos of people like Raffan doing it, he didn't seem to have any trouble. ( And please don't say,"well you're not him!) More pressure probably would have helped, but things get too hot when you do that. What do you suggest? I don't particularly want to fool around with steady rests.
If you need more pressure from your left hand it means you need less pressure on the bevel of the tool. There are actually several solutions that all need to be put together to solve it.
First is to put as little pressure from the tailstock as possible. You might need to drive the center into the wood with a wooden mallet or even cut slots so that the drive center doesn't need a lot of pressure from the tailstock.
Next is to turn the middle first leaving the wood fat on both ends to reduce the vibration.
It should go without saying but a really sharp tool needs less pressure to work. Then while your turning try to put as little pressure on the bevel as you can. Less pressure from the bevel means less pressure from your hands is needed and there fore less heat. If it still persists try reducing the speed of the lathe.
If the chatter has already started change the angle of the tool so you aren't riding with the chatter. You want to just remove the tops of the chatter and changing the angle will help.
Last but not least. You need as many years turning as Richard Raffen. Well lots of practice doesn't hurt.
What John said for everything else but adding tool advice. Scrapers or flat carbide insert tools make vibration worse. Shearing light cuts are a necessity. So a skew it is!
The wood being used is another factor. Stiffer wood is less likely to flex. Uniform density is also desirable - if the blank is heavier on one side because of uneven growth rings, a knot, and such it will have a built-in tendency to flex.
I THINK it was Raffan that also said if your support hand gets hot you are using way too much pressure with the tool! I sometimes squeeze the wood between my fingers rolled over the back and my thumb on the skew, but lightly, very lightly. The thumb mostly steadies the skew. I turn a lot of spindles, most pretty thin. (1/8"-1/2")
One thing that really helps me is to not turn between centers but grab the headstock end tightly in a chuck. This removes one pivot point and stiffens the left end considerably. A jam chuck works well too. I usually mount between centers and turn a tenon of some sort for the chuck - this is better than grabbing the square blank. I use a chuck with maybe 99% of my spindle turning!
Be sure tools are sharp, very sharp, honed and perhaps polished. I mostly use a skew sharpened at about 40 degrees.
Besides starting with good, strong straight-grained wood, here are a few other things I try when I run into problem vibrations and chatter. Notice I said "try" - I sometimes have to experiment until I get it to work:
- Reduce OR increase the tailstock pressure.
- Switch the direction of the cut, towards or away from the tailstock
- Waste wood away with a narrow parting tool to get close to the final diameter
- Try a skew with a different grind angle.
- Try a thicker or thinner skew - the thickness and angle of the grind define the length of the bevel which puts more or less bevel against the wood.
- Try a spindle, bowl, or roughing gouge instead of a skew. A relatively small diameter, deep flute roughing gouge often works very well to cut chatter.
- Change the lathe speed. Sometimes faster even helps! I typically turn long spindles at a very high speed, often at 3200. (with one end held tightly in the chuck)
- Press the shaft of the tool tightly into the tool rest. This may require a bit of ballet to do that AND keep the cut light, but hey.
- As mentioned, sharpen and hone. Perhaps often.
- As mentioned, use a light cut. A very light cut.
John L's point about the existing ridges from chatter making the problem worse is a good one! What I often do in this case is use the skew a different way for just one pass to cut away the ridges: cut with the very point of the "heel" of the skew instead of the edge. This may roll up the grain and will NOT give the cleanest surface but that single pass may take off most of the ripples and get you back to a nice round blank.
One formula is hand pressure = tool pressure. So, you should be just barely touching the wood with both your hand and the tool as in 'the bevel should rub the wood, but the wood should not know it'. If your hand is getting hot, you are pushing too hard. Takes a lot of practice.
The advice from John Lucas and John K Jordan is dead on! Of all the various points they made, from my spindle experience two I have found crucial with long/skinny spindles are
-- hold one end in a chuck -- you will have far less vibration
-- begin turning at the center, then work toward the tailstock, and finally toward the headstock
A spindle that diameter relative to length is going to have some vibration.
My physics is a bit rusty, but the vibration we experience with long spindles is due to deflection of the middle section of the spindle either due to end pressure causing a bending moment which gets worse as the spindle gets thinner; or tool force causing the deflection which is proportional to the tool force applied. Blunt tools or poor tool presentation make this worse. Both John's have given possible remedies.
Holding the long spindle between centers can cause both problems.
However when we mount one end, usually the head stock end in a fixed mount i.e. a chuck, we actually modify the bending moments & deflection along the length of the spindle.
If we introduce a spindle steady rest we further modify the spans between support and the amount of deflection.
At times you can actually notice a "sweet spot" along the spindle where there does not seem to be any vibration (deflection). This usually occurs at an inflection point, i.e. where the deflection is zero.
Some turners have experimented with holding a long thin spindle i.e. a trembleur in tension during the whole turning process.
>My physics is a bit rusty, but the vibration we experience
>with long spindles is due to deflection of the middle section of the spindle
This is certainly true when spindles are flexible and anything done that gives more support will help. With the non-homogeneous nature of wood other factors can come into play, even when the wood is essentially inflexible.
I recently experienced this on the end grain of a thick block of elm where no deflection was possible. The structure of the wood caused a minor deflection (sort of a bounce?) of the tool at certain spots which was amplified by the bevel contact on every rotation. Until I fixed it with a firmer grip and a slight change in presentation I had a beautiful ripple going.
Some spindles show the same effect, which John Lucas described and I have seen often. I've had some particular pieces that were much worse than others even when otherwise apparently identical in size, species, and even cut from the same tree. In "long" spindles the effect is probably both started and amplified with too much pressure from the tool, at least in my experience.
Yes i have experienced that with spindle blanks, particularly with wood that has varying density. Closer growth rings on one side of the blank or small knots etc.
Two more things that I don't think have been mentioned. I have done a number of long thin spindles without a steady rest. I whittled or sanded one end to drive it directly into the Morse taper of the head stock. Was surprisingly easy to get it to fit. This way you don't have chuck in the way and you don't have to have much pressure on the other end to drive it.
I have a piece of High Density Polyethylene (HDPE) and I made a little concave block out of it to use to steady things. Very slick and does not leave a mark on the spindle and keeps the heat off your hand.
Elliot, the sequence of cuts becomes important on long thin spindles as you are finding out.
When you watch production spindle turners like NZ'er Shane Hewitt etc you will notice that they mark out the spindle then work on the larger details such as pommels and beads then work on the next largest diameter elements such as torus, ovolos, fillets, quirks, long ogees etc and work down to the smaller neck & cove elements last. By working in this method you retain the maximum possible stiffness in the blank for as long as possible.
I have attached a diagram which is a redraw of the original from an early AAW journal.
I've never heard of some of these terms, so they must not be used much. I'm still trying to get folks to stop using "tendon" when they mean tenon (to describe something that is actually a spigot, but hey, who's counting).
Rabbits do have tendons (helps them get away from carnivores), but rebates fit spigots (mortises fit tenons). That's enough geekiness for today, I suppose
I 'bout went cross-eyed too. The figure is numbered from the bottom up and the key is numbered from the top down. This caused the TE (Technical Editor) node in my right frontal lobe to nearly spring a leak. This, in turn, almost caused me to write "your" instead of "you're" in a forum post.
However the list is otherwise excellent. I think I will print out the document and tape it inside my truck windshield. If I memorize it maybe I can impress the other farmers down at the co-op.
Don't shoot the messenger. I simply redrew the original to make it easier for clubs to incorporate in digital publications. I did rationalize the inset. Good point about rearranging the text layout. Maybe one day when I get a chance I will re do it.
>Maybe one day when I get a chance I will re do it.
When you do, make up names for these:
(not my photo)
I currently refer to them as the "curved transition thingy on the squarish part" at A and for B the " wide-ish flat part". These are somewhat consistent with my other references to the "squished beady thing" and the "kind of a cove".
When you make up new names I recommend using names from Greek mythology, as in "next, cut a 4mm Poseidon between the the large Zeus and the curvy Aphrodite."
My point exactly. But if the authoritative reference can call a fillet above a plinth a scamillus, maybe the fillet next to the pommel should have a special name too so its feelings won't be hurt. Perhaps it could have a different name if next to a lamb's-tongue pommel than when supporting the beaded pommel shown. This is so complicated!
And where is the basic cove in the diagram? Must we all learn to pronounce cavetto instead? At least they list the bead! (Whew!) But where are half-beads? And half-coves?
It appears on second look that the master list is not yet complete. I have taken it off my windshield until version 2.0 is released.
A few spindle illustration/terminology suggestions
John K Jordan
>I'm open to more suggestions for improvements though.
It has come to my attention that some people actually use lathes to make functional things instead of just prettys to hang on the tree or sit on the shelf! I am shocked!
Perhaps an authoritative reference would comprise both the expanded original and a separate diagram or two for those who turn legs for furniture. Sub diagrams could illustrate variations for clarity, such as the types of pommels.
In addition to adding the cove and pommel, other variations might be nice. Two that come to mind are the standing bead and inset bead. This might simplify notes and communication where the words "standing bead" could replace "bead cut to stick up higher than the wood on either side."
How about illustrating specialty features like spiraling, texturing, and fluting. The first two are turned with the right tools while the flute, while not technically "turned", is certainly a legitimate part of finished spindles.
(Photos borrowed from internet)
For the table legs, parts of the Queen Anne style turned off-axis might be shown and named, specifically the half cove and half bead:
Wow, I can see a well done update worthy of a new magazine article. A comprehensive article could include photos and tips for turning at least some of the features. I see it now, your picture on the cover, famous, the book offers and money start pouring in... :-)
Well lots of practice doesn't hurt.
My part was to help out the editor of a club magazine by making the original more presentable.
