Need some ideas to correct a turning problem.

[Rangertrek]

Something new developed on the last few pens I have been making. I am getting tiny "spiral ridges" on the barrel. I am trying to track down the potential causes of this problem so I can begin eliminating them one by one.

The lathe is bolted to the bench, so no movement or vibration there.
I am using a mandrel and the shaft is straight. Using a 60 degree live center that I have had for more than a year now. No heavy pressure is applied to the shaft or the lock nut. The problem is most apparent when I am using a rounded skew. Made 100s of pens and never had this problem.

Any ideas?

 

[jimm1]

Do your tubes fit snug on the bushings? Are the bushings snug on the mandrel?

 

[Rangertrek]

Yes, tubes and bushings are snug on the mandrel.

 

[ed4copies]

John,

"Spiral Ridges"??
Is this a plastic blank? IF so, heat??

 

[PenMan1]

John,

"Spiral Ridges"??
Is this a plastic blank? IF so, heat??

Ditto, too much heat. Either pushing the tool too hard or a dull tool is the likely culprit.

 

[Rangertrek]

No plastic this time, first showed up on some antler and then on a piece of maple. The ridge (or valley) is a spiral from blank end to end direction. Almost appears if skew is "dipping in" causing a little valley. I have noticed a little "bumping" as the blank turns and hits the skew.

 

[ed4copies]

Sharpen your skew and turn up your speed and pay attention (no mind wandering for a pen or two), see if the "thump" continues---that is probably a symptom, just have to figure out the disease.

 

[Brooks803]

also check your skew for any chips or defects.

 

[jimm1]

Tail stock???

 

[Smitty37]

I've seen this...

Far from being expert but I've see something similar....It went away when I switched to a very sharp tool. In my case I think I had a dull gouge.

 

[rogerpjr]

check the alignment of the head and tailstock, both horizontally and vertically. It doesn't take much for them to be misaligned enough to see problems.

 

[Mark]

Agreed with what's been suggested. I'd think it was "burning" the blanks. (read, getting to hot and melting it)

I've also seen ridges in the CA when using a particular brand of paper towel. For me, Bounty towel cleared that up.

 

[ed4copies]

No plastic this time, first showed up on some antler and then on a piece of maple. The ridge (or valley) is a spiral from blank end to end direction. Almost appears if skew is "dipping in" causing a little valley. I have noticed a little "bumping" as the blank turns and hits the skew.

Are you saying it runs in a straight line from end to end, or that it runs around the blank, from end to end (like a snake curling around the blank?)

 

[aggromere]

I had this same symptom on a closed end pen I was turning. The culprit was I somehow did not seat the collet properly in the chuck and the pen was turning out of alignment (not perfectly straight). I did not notice it when finishing the pen but upon inspection I had the same spiral pattern. My vote would be something isn't aligned properly, could be the mandrel or tailstock or live center.

 

[Rangertrek]

UPDATE UPDATE !!
I did some testing and checked the alignment on everything. I believe the problem was with the operator (ME) and not in the equipment. I think I got sloppy with my techniques. Worked on some scrap wood and everything was good, using both a mandrel and between centers, using various tools and the skew. I also jumped up the speed on the lathe and have better results.

I learned from my own mistakes on this one. In computer lingo, this would have been a PICNIC problem. (Problem in chair, not in computer.)
From now on when I get a little problem, I am going to sit back, relax, and see what changed from prior successful turning, and generally figure its me doing something different.
Thanks for all the ideas and comments.

 

[ctubbs]

Way to go John.
Charles

 

[jttheclockman]

Just for future checks. There are times when something like that can occur from the tool rest. If you use the wrap around technique you can be vring the pressure applied down the blank. If you use the finger sliding as a guide there can be divots or such in the rest. Can make a difference as the tool slides with it. Just some more thoughts.