What causes skew chatter?

[leehljp]

I am getting small a amount of chatter with the skew on my pen lathe. What would be the causes of this? The harder the wood the more it does. The gouge cuts smooth as butter.
Very light touch eliminates it but it is very slow go at this rate. It is not too bad that cannot be sanded out, but it just doesn't seem to me that any chatter is normal, but then I am new to this side of woodworking.

The skew is very sharp (I have some fine Japanese water stones.)
The mandrel is tight and centered. Finger tight, hand tight, and even lightly using pliers to tighten the blanks, same result.
Live center dead on, spring loaded pushed in about 1/2 inch.
(Had a regular center but it did the same.)
Chatter occurs on the blank of the tail stock end only.

I am using a Taig pen turning lathe. (It was all I could get in my suitcase to bring back from the States.)

I checked the archives and only two mentions of chatter and one had to do with talking!

Your input is appreciated.

 

[crash]

i had chatter when i did not tighten the tail stock enough against the mandrel.. try a little more pressure on the mandrel.. it should eliminate your chatter..

 

[Mudder]

Originally posted by leehljp
<br />I am getting small a amount of chatter with the skew on my pen lathe. What would be the causes of this? The harder the wood the more it does. The gouge cuts smooth as butter.
Very light touch eliminates it but it is very slow go at this rate. It is not too bad that cannot be sanded out, but it just doesn't seem to me that any chatter is normal, but then I am new to this side of woodworking.

The skew is very sharp (I have some fine Japanese water stones.)
The mandrel is tight and centered. Finger tight, hand tight, and even lightly using pliers to tighten the blanks, same result.
Live center dead on, spring loaded pushed in about ? inch.
(Had a regular center but it did the same.)
Chatter occurs on the blank on the tail stock end.

I am using a Taig pen turning lathe. (It was all I could get in my suitcase to bring back from the States.)

I checked the archives and only two mentions of chatter and one had to do with talking!

Your input is appreciated.

Only thing I can think of is that you are not riding the bevel. Or possibly that you are using your hands instead of your body to turn.
I went to an Ellsworth class and he stood there and held me in a bearhug to force me to use my body instead of my hands.

Maybe someone else has better idea's.

 

[leehljp]

Mudder,

I did use my hands and arms; I better try putting my body into it.

Riding the bevel, I read that somewhere - I will have to look that up as I do not know that technique. Found one reference to it in "search" but nothing on technique.

I will also try the tightening of the tail stock more, but it seemed quite tight.

 

[woodscavenger]

I get that occasionally as well. Sometimes the chatter makes a cool multi-spiral shape that I wish I could duplicate on purpose. I tried the same things as you to fix it but I think mudder has it right. But a little more stabilizing force behind the tool. THINK of pushing through the long axis of the skew. You usually only need to tighten up the pressure behind the skew and not really push it harder into the wood. I think if your back pressure is too light the harder woods push the skew out of the cut and you minimal back pressure pushes it back in and you get this resonant chatter.

Another thing I found is that on some woods that I have chatter problems (some cocobolo I turned this morning) that I have the skew at to acute of an angle (meaning my skew handle is way off to the side) so I bring the skew around to a less acute angle and increase my back pressure (with big long handles you can lock it to your hip, and with shorter tools you can snug your forearm and elbow against your ribs)big leaning into it just a little.

 

[JimGo]

Hank,
If you're searching for "riding the bevel", you may have trouble finding it. Try "bevel rubbing"; that's what Richard Rafian (sp?) and several others call it. I'm still working on something that resembles the technique, but it works well. Basically, the surface under the sharp end of the gouge/skew/etc., the really shiny part, is the bevel. As you present the tool to the wood, the wood should just barely touch that part. Then you apply slight downward pressure, and the wood will start to encounter the sharp edge instead. This results in nice easy cuts.

I'm sure the other, more experienced turners can elaborate, but hopefully this will give you something to play with in the mean time.

Good luck!

 

[ctEaglesc]

Sounds crazy but I liken it to symapthethis vibration.
I use a skew (actually a 1&1/2" wood chisel) to "straighten out" my blanks after the gouge)
I makes no difference whether it is a piece of antler that has a curve to it or an piece of rock maple.
I get less chatter when I backoff on the speed so I chalked it up to SV.
It gives a real cool effect on Corian.

 

[leehljp]

The worst chatter was with cocobolo. I didn't mention that it occurs when I am about to get the last half of a millimeter for final sizing before sanding, and I'm basically using a scrape cut and getting fluff instead of any kind of shavings.

I am using an 18 in skew from PSI but I have a good set of about 24 in chisels packed somewhere from a move a year ago. I don't know how good they are but there are 6 in the set and cost about $120.00 20 years ago. Thanks fellows for all the info.

I need to learn some basics as well as techniques. But this is FUN!

 

[Mudder]

Originally posted by leehljp
<br />......... and I'm basically using a scrape cut and getting fluff instead of any kind of shavings.......

ahhh..... I only use the skew for planing cuts, beads and the like, I've had the same problems trying to use a skew as a scraper. You can try to stabilize the cut with pressure from your finger but I ran out of patients trying to use the skew as a scraper and I learned to do planing cuts.

Sorry Hank, All I can suggest is that you take light cuts and stabilize the cut as mentioned above.

 

[leehljp]

Mudder, or anyone else that cares to get in on this:
That brings up another question then, how do you get the final 1 millimeter of a cut. I love slimline pens for myself, and in making them I need straight cuts. I use the gouge to get down to within a mm of the bushings, but to make the pen blank straight and level from one bushing to the other I need the skew. I am skeptical about making planing cut once I get that close, so I have been doing the fluff cuts as Raffan notes in his book. And then the chatter. But it isn't bad.

Should I be trying another chisel or cut for straight / level cuts over a length?

 

[DCBluesman]

Final millimeter? If I'm down to within a millimeter of the bushings (or the caliper measurement), I find that 220-320-400 sanding brings me home. The higher grits take off so little that I don't much figure them into the equation. If you think it's important to remove this with a turning tool, you might consider a scraper since they are designed for scraping instead of cutting or gouging.

 

[Rifleman1776]

"I am getting small a amount of chatter with the skew on my pen lathe. What would be the causes of this? "
You need to get a male skew. They are quiet. Only female skews chatter. You are lucky to be getting only a small amount. []

 

[C_Ludwigsen]

I usually get skewed chatter when I'm not paying proper attention to my wife. And when she notices, the chatter has a tendency to get louder and faster....

OH WAIT!!! SKEW chatter... Oh, I sometimes get that if the tools is a bit dull, the mandrel is under too much tailstock pressure (flex), or when I change the tool presentation to the wood by not moving my body consistently along the length of the cut.

 

[woodscavenger]

I guess you guys are posting this at work? If your fair ladies catch you I'll bet the amount of time you spend/sleep in the shop with increase......[]

 

[Rifleman1776]

I couldn't help myself. [] Mea culpa for straying from topic. [:I]

 

[leehljp]

I needed the laugh! []

Lou, My old instinctive woodworking habits dictate that the blade cut precisely - but this is not a saw! OK, so now I learn what a Scraper is for. I'll go find my old but unused chisels. There must be one in there. If not, then I will have to order me one.

So the apparent problem is - wrong tool! Thanks. (I will make sure that I get a male scraper.)