# mandrel vibration



## JHinkson (Dec 24, 2012)

I'm new to the group.  I've been bothered by mandrel vibration while turning pens for a long time.  It is especially troublesome when I am using a skew chisel.  It is not a problem when I'm working near the taper.  The  woods cut cleanly there.  On the other end near the live center I get mandrel vibration that makes getting a smooth cut nearly impossible, so I'm left with a lot of sanding.  Any suggestions?  I keep my chisels sharp.  I've tried adjusting the turning RPM.  That doesn't seem to help.  I'm using a Jet mini lathe with speed control.


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## Bill in Buena Park (Dec 24, 2012)

I haven't encountered this myself yet, but you might want to ensure that the live center is a proper fit for the mandrel (I believe 60 degrees is standard), that it seats snuggly into the mandrel.  This assumes there are no tolerance issues with either the mandrel or live center...


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## firewhatfire (Dec 24, 2012)

welcome to site first of all and

get one of these to start with. It will help on part of it. I also only turn 1 barrell at a time when doing it this way. The other option is turning between centers. Nothing to vibrate there.


PSI Woodworking Products PKMSTS2 2 MT Live Mandrel Saver - Amazon.com


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## frank123 (Dec 24, 2012)

Tailstock to headstock alignment, too much pressure on the mandrel/mandrel not straight with the axis, live center itself not precision made, bad taper angle or alignment in either tailstock or headstock, all kinds of things.

If you have a dial indicator and base, check to see if it is running true at both ends (or turn it on slow and watch the mandrel turn without the live center engaged.  That would give a starting point for further diagnoses otherwise I suppose hit and miss is the only thing I would try.  If you have the capability of making an accurately center drilled piece of known round material (such as drill rod) or know someone that can make yo one -very easy on a metal lathe, maybe not possible withoutone- you could put that between centers and just feel (or measure) whether or not there is and wobble at the tailstock that is not felt at the headstock.  Perfectly smooth turning at both ends would eliminate most lathe problems and put it more likely on the mandrel or the way it is being used.

TBC eliminates mandrel problems, once I tried it I haven't used a mandrel again.  (I still consider myself a beginner at wood lathes and hand turning stuff, so take what I say under consideration as such, but I have a good deal of metal lathe experience on small metal lathes)


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## trapper (Dec 24, 2012)

I agree with the comments of tailstock alignment. However, are the bearings true in the live centre using too much pressure by advancing the tailstock to tightly can flatspot the bearings this will cause oscillating and vibration (whip) of the mandrel stick. Also make sure the dimple on the end of the mandrel is clean and or the tip of the revolving centre is also clean.
Finally, I'd check bearing wear in the headstock. Id be surprised if it is abearing problem as I'm guessing your lathe is fairly new. One totally final thought is the sleeve of the quill clean... if not so this could cause the taper of the centre not to sit true


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## John Den (Dec 24, 2012)

I was plagued with this vibration, particularly using the skew, with the diagonal ripples that I coud ony sand away! Then I read , on this site, about the advantages of Turning Between Centres - bought myself a dead centre to drive the blank at the headstock end (I'd already got a live, revolving centre for the tailstock end).
All my vibration problems have disapeared and the skew is a joy to use!
Try it and see.
Regards,
John


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## George417 (Dec 24, 2012)

Is your mandrel a fixed length or adjustable? If it's fixed length I suggest
you get rid of it and get you an adjustable.
The fixed length has a tendency to flex, or start turning between centers
I have started to make bushings that allow me to turn between centers and it works great.


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## its_virgil (Dec 24, 2012)

I find it amusing that every time someone has a problem turning pens on a mandrel that the number one solution often turns to turning between centers. Now, don't get me wrong, I have nothing against turning between centers using the special TBC bushings or not. It is a great way to turn pens, but so is using a mandrel. I turn on a mandrel and have no problems with any of the issues that are often questioned. There is a solution to problems associated with turning on a mandrel. 

Often out of round pen barrels get that way while sanding, not while turning. The grain on a pen barrel changes as the barrel spins. Sanding can remove more material on one side of the barrel than on another producing out of round pens. Try less pressure when sanding.

Dull tools often cause chatter, vibration or the ridges. Dull tools require more (pushing) pressure which can flex the mandrel also. These problems can also occur from having too much distance between the tool rest and the pen blank.  Incorrect tool usage can also be problematic. Presenting the tools at the correct attitude and angle to the pen barrel will help them cut more efficiently. All of the classic solutions like alignment, tail stock pressure and brass nut pressure need to be addressed.  Having a 60 degree live center to fit the dimple on the end of the mandrel is also a plus. Using the stock live center that is supplied with several mini lathes is not satisfactory.

Turning between centers is successful, in my opinion, because just one blank is on the lathe. Get an adjustable mandrel and shorten it to turn one blank at a time. This will solve many problems due to less flex on the mandrel. For the pens I make most I have reamed the bushings so they will fit on the B mandrel which is stiffer due to its larger diameter. Shorter and stiffer make for a better mandrel and pen turning experience.
Merry Christmas to all and may the new year bring perfectly round pen barrels no matter how the problems are solved.
Do a good turn daily!
Don


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## Davej_07 (Dec 24, 2012)

I've found a problem with the bushings being out of round. I think the center hole is ever so slightly off. When I check the mandrel with no bushings there was no wobble, but the bushings were way off according to my dial gauge.
I've started turning with a caliper and I made a drive center from some scrap hardwood. So far it works great, just slows the process down due to one tube at a time.

Dave


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## Boz (Dec 24, 2012)

Again I want to welcome you to this site I am sure you will learn quite a bit.  When you bring the live stock to meet the mandrel does it flex at all?  If so your mandrel in either bent or not centered.  Take everything apart and clean the tapers and the mounts.  If it is still not meeting exactly straight try clocking the headstock and see if there is a position where they meet and there is no flex.  Not a perfect fix but will work.  Also do not over tighten the nut on the mandrel or drive the head stock in so tight that it flexes the rod.  I find that you should always tighten the nut on the mandrel after you have set the live stock.  
Now I am going to take a left turn on the previous suggestions.  How are you holding the skew?  If it is too flat you will get chatter.  Experiment with different angles to find what works for you.  I was getting annoying chatter on acrylic blanks then I started playing around with how I held the tool and started throwing long strings with a very smooth  resulting surface on the blank.  
Good luck.


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## its_virgil (Dec 24, 2012)

I once had a drawer in my tool chest that was full of "bent" mandrels. I purchased a Beall Collet chuck and use it to hold my mandrel and magically all of those bent mandrels became straight when placed in the Beall collet chuck. I found out that my tapers were not clean and the mandrels would wobble. So, Boz's advice is sound. Dirty tapers can cause problems. And, Davej_07 has good advice. Not all bushings are created equal, to specs or even concentric. I have had several sets that were useable. Bad bushings should be replaced by the vendor.
Do a good turn daily!
Don


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## JHinkson (Jan 4, 2013)

*mandrel vibration question*

Fellow penturners,
I am overwhelmed by the responses to my questions about vibration.  I've followed "firewhatfire"'s advice and ordered the PSI Live Mandrel Saver because it makes good sense to me.  If I still have a vibration problem, I'll do my turning between centers as suggested by several folks.  I didn't know exactly what that meant until I did some searching and found a nice YouTube video on the subject.

I'll report back when I've tried the mandrel saver.

Thanks so much for the great feedback

Jim


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## Dalepenkala (Jan 6, 2013)

Not much for me to add so Ill just say welcome to the IAP!


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