Chatter/slight oval pens

[willow]

Hello everyone!!

I am a new member to this site. My name is Denise. I have been turning for about 10 months now. I started with bowls and now I am turning anything I can get my hands on since I fell in love with this beautiful addiction!!!:biggrin::biggrin:

I need help, lately when I am turing pens, I get a chattering on the blank, which is both visible and audible. And some of them are coming out slightly oval. What is causing this? I usually turn wood or acrylic blanks with a spindle gouge until I get full round, then continue with a skew. Am I applying to much pressure? I thought for sure it was the mandrel, so I changed out the mandrel rod, but it still continues. Is my tail stock not aligned properly with my headstock? What causes this?:frown:

 

[1080Wayne]

Denise Are you sure your tools are sharp ? Dull tools automatically lead one to apply more pressure , and can cause chattering . Wayne

 

[LEAP]

Along with tools that are not scary sharp the other leading cause of out of round is too much pressure on the tail stock and the knurled mandrel nut being to tight. Either one will put a slight bend in the mandrel and cause out of round.

 

[monkeynutz]

Your mandrel rod might itself also be slightly bent... Try spinning it with the tailstock pulled slightly away from the mandrel, and watch the end of the mandrel rod for concentricity... You can also run the mandrel bare, and feel for a wobble with your fingers.

 

[marcruby]

1. As others have mentioned you tools have to be extremely sharp. I'm assuming you're using a skew.
2. Also as mentioned, excess pressure can cause the same symptoms.
3. Under pressure the mandrel rod will sometimes bend permanently. That will cause a permanent fit problem.
4. If your skew is sharp then look carefully in how you're using it -- are you rubbing the bevel? Also try adjusting the angle and cutting point of the skew. Missing the sweet spot can also cause chatter.

Marc

 

[randyrls]

Hello everyone!!

I need help, lately when I am turing pens, I get a chattering on the blank, which is both visible and audible. And some of them are coming out slightly oval.

Denise; I will take a slightly different tack. Mount your mandrel on the lathe with nothing on it. Snug up the tailstock. Turn the lathe on and lay your skew across the mandrel. Do this at the headstock end, middle and tailstock end. Does it vibrate?

Now mount pen blanks and bushings on the mandrel. Repeat the test above. Use caution to touch only the bushings, and not the blanks.

This should give you a good idea of where to look.

I have had this same problem, but it was because my blanks didn't have square ends. When snugging up the brass nut, it is easy to "pull" the mandrel out of true.

 

[cozee]

As mentioned several times already, sharp tools are a must.

To go a step farther than Randy has, check your lathe. Take an put the live center in the tail stock and a dead or spur center in the head stock. Slide the TS up near the HS and tighten it down. Now extend the live center forward till it just about touches the other center. If they line up spot on then you can eliminate any lathe misalignment. If the tips of the centers do not line up, here is yet another source for the oval shaped pens. One can correct this by using thin brass sheet stock to shim as needed. The brass stock can be found at most well stocked hardware and hobby stores. K&N is one brand name.

 

[leehljp]

One other thing that I didn't see listed above: Are you using a 60° live center for the tail stock? NOT using a 60° center could be part of the problem.

AS already mentioned, there can be several causes. Because of 1. those reasons, 2. the occasional glueing of blanks to the bushing, and 3. bushing sanding dust on a blank, . . . many have forgone the mandrel and now use the mandrelless, a.k.a. "no mandrel", a.k.a. "turning between centers" method.

The "no mandrel" method eliminates several problems that crop up with mandrels simply because the mandrel is not there. It doesn't cure a dull cutting edge, but it eliminates the chatter and OOR - Unless the tail stock is out of alignment or the bushings are OOR themselves.


I just noticed that you did several Sierra pens. Early on (two years ago) the first batches of Sierra bushings had a high rate of OOR. Even since then and after they were supposedly corrected, I have had two of 6 bushings to be OOR. Even minute' OOR will amplify chatter.

 

[willow]

I fianally figured it out!!!!..........and it's not good

Hello again to everyone!!!

Thank you all for your brainstormong as to my problem of the vibration/chatter when turning pens. All of the suggestions you all had posted had either already been tested or tried, and at least got my mind going as to what else it could possibly be. Recap; all gouges and skews are very sharp, I have a live centre in the tail stock, the mandrel rod was tested and replaced three times, all with the same the same results.

So.........again this morning I am attempting another pen with confusion as to what is causing this.........and then I stopped working becuase i noticed something.

First off I have a General international 25-300 MI lathe.

The spindle is NOT staight it is bent!!@! When I took off the pen mandrel, and replaced it with a spur centre, brought up the tailstock with the live centre in it, the points are pretty close , BUT when you turn the spindle by hand you can see it move in a jump/out of round pattern! UUUGHH! To test my theory I took a dead centre and repeated this process, same results. I then repeated this experiment on my mini lathe, and there is a huge difference. The mini lathe runs totally true.

I know I should have caught on to this awhile ago, but your thinking that a brand new lathe, nothing sould be wrong with it, right??? Wrong. I attempted to turn two bowls with this lathe and the first one only 6" big kept changing the centre as I was turning, cunfusing, as it was 90% dry, and then I was doing a final scraping on the outside of it a BAM! it exploded and broke. Okay onwards....
Then recenlty I was working on a big poplar bowl, and it was at least 50% wet, I turned the outside of the bowl but could never seem to get a vibration out of it/ or totally round........thinking that it was out of balance due to more moisture on one side, I took it off of the lathe for "another day" project.

Now I am back to pen turning and this vibration got even worse, and the moral of the story is I have a spindle that is not true, and to top that off my variable speed switch works intermitedly, sometimes yes sometimes no. I had to turn on my lathes 5 times this morning before the spindle would start to turn! looks like I am going to need some repiar/warranty work done to my new lathe

Not looking forward to this. Anyways I have put a call into the rep for General International to see if we can get this fixed, and now I wait, but at least I have my mini lathe that I use my Bealle buffing system on that I can turn in the meantime.

I thought I read in a post somwhere that someone else had problems with their variable switch on a 25-300 MI GI lathe? Has anyone ever had a spindle problem like this?? I purchased this lathe in May and haven't had a lot of use on it, maybe 12 pens and the two not so round bowls.

Wish me luck on getting this fixed, Thank you to all who helped in this matter.

Denise.

 

[leehljp]

Denise,

Your spindle problems sounds like it could be the 60° problem. In the reply you mentioned "live center" but you didn't mention 60°.

Bent tips on spindles are common when one puts a spindle made for wood - into the small cup of the mandrel, which is meant for 60°. If you buy another wood spindle, it will happen again.

The mandrel is metal, and as such, it requires a "metal" lathe spindle which is 60°. There have been many discussions on this forum for the need of 60° live centers. This is not an "option" for upgrading, it is the standard basics if using a mandrel.

 

[ironman]

no matter what do not snug up your tailstock to the mandrel if there is the slightest bit of too much pressure it will make your mandrel bend

 

[holmqer]

On the lathe with the bent spindle, do you get wobble with a chuck or just with a center?

If just with a center, you may just have some debris in the bore.

If you feel the inside of the bore, it should be smooth as glass.

 

[MobilMan]

Try changing speeds when it is vibrating. Everything has been going good until the other night. Was turning a pen with Ebony. Got it round & it started to chatter/vibrate. What The............what happened? Was turning about medium speed so I cranked it up to a higher speed. Ran smoother & was able to smooth the blank with the gouge. Last night-same thing on walnut, tried a diff. speed & it did away with the slight wobble. Figger that one. Maybe it's like our car tires..at a certain speed it can vibrate.

 

[marcruby]

I just noticed that that particular General isn't well rated, which surprised me. Anyway, the first culprit to check is the morse taper. Make sure you haven't leaked some glue or guck into it that is forcing the fit off center. Another thing to test is the 1"x8 headstock joint put a chuck onto the headstock and make sure it us turned down firmly. See if you have any vibration. turn a simple disk and see if you have a problem or if it's out of round.

My next question is how the spindle moves relative to headstock itself is it steady relative to the headtock. Is it steady relative to the ways. None of these tests bode well if you find something wrong but it will give you some idea of the magnitude of the problem.

I forgot -- make sure that the headstock is firmly bolted down. Loose bolts could easily cause the problem you describe.

 

[Jrcollins]

It's been a while since I've been on. But having just partially mastered the skew, I had some similar issues with chatter. So I'm merely looking for clues. Thanks again.

 

[jttheclockman]

It's been a while since I've been on. But having just partially mastered the skew, I had some similar issues with chatter. So I'm merely looking for clues. Thanks again.

Wow Jack this is a very old thread you dug up. But first let me be the first to welcome you to the site and glad you found us.

Next this topic comes up alot and I did a quick search for you and here are some past threads on the topic that could help.
https://www.penturners.org/search/86365/?q=chatter+when+turning+pens&o=relevance

But to quickly sum a few things up to look for is sharp tools, proper angle of presentation of tool to the material, steady the tool, make sure the tool rest is close to the material, if using a mandrel make sure it is not bent (this can cause both out of round blanks and also chatter) , would be better to turn one blank at a time to see if this helps with chatter and shorten the mandrel length. (closer to the head stock the better for support), and finally some materials in the acrylic family are notorious for chipping and tough to turn especially for a beginner. Hope some of this helps. Good luck.