Question for you Pen Turners...

tom_k/mo · Post by **tom_k/mo** » Wed Dec 09, 2009 4:05 pm

Just received a new catalog in the mail from Penn State Industries, and it had some neat new stuff that's not even on the web site yet. One thing peeked my interest (at first)...
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Looking at it though (and if I read the description correctly), it looks as if you don't use the knurled jam nut on the end of your mandrel, but instead let the mandrel pass THROUGH the center and the end of the center butts up to your pen bushings directly.

As I figure, this would require the lateral pressure on the quill to be great enough to keep the blank from turning on the mandrel. I know I have to crank down on my jam nut now pretty good to keep some of my blanks from spinning on the mandrel when turning, I know I sure don't put as much pressure on the quill (pressing the mandrel against the live center) as I do on the jam nut to keep the blanks from spinning on the mandrel. I can see if you were using a conventional lathe with a screw advance mechanism on the tailstock to tighten the center, but I'm really sceptical about trying to apply that much pressure on the quill advance lever and having to crank the headstock lock (to lock the headstock to the way tubes) tight enough for this to work on a ShopSmith. What do you think?

judaspre1982 · Post by **judaspre1982** » Wed Dec 09, 2009 5:10 pm

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mbcabinetmaker · Post by **mbcabinetmaker** » Wed Dec 09, 2009 6:41 pm

I think you could still use it in conjunction with the jamb nut. Just run it up against the nut with average pressure.

fjimp · Post by **fjimp** » Wed Dec 09, 2009 8:05 pm

This looks interesting. One Mandrel I favor allows adjusting the length. I find that improves ability to turn without bending Mandrel. Still I believe the Jam Nut is the leading cause of blanks that don't fit together in the center and bent mandrel's. I can't wait to try one out. Jim

iclark · Post by **iclark** » Thu Dec 10, 2009 12:06 am

fjimp wrote:Still I believe the Jam Nut is the leading cause of blanks that don't fit together in the center and bent mandrel's.

Jim,

could you say some more about this please? I'm not sure I follow (and my PSI mandrel came in this week).

Ivan

fjimp · Post by **fjimp** » Thu Dec 10, 2009 9:28 am

iclark wrote:Jim,

could you say some more about this please? I'm not sure I follow (and my PSI mandrel came in this week).

Ivan

Ivan,

The the jam nut is often a difficult item to adjust properly. Left too loose and the blanks spin which makes turning them nearly impossible. The tendency is to tighten them good and tight which tends to bend the mandrel. Once bent the pens segments become bowed and do not turn evenly. I have a bent mandrel that I have attempted to straighten. I really thought I had it right and attempted to turn a couple of Mini Bullet Twist Pens. The blanks appeared correct on the mandrel yet once assembled are out of round.

Now I need to be careful here I use two different lathes to turn pens. The Shopsmith lathe due to design does not allow the mandrel to shorten by the tube sliding into the headstock mounting. Thus that new Tail Stock Center which does allow the mandrel to shorten thru the tail stock would solve that issue. My other lathe is a Mini Jet Lathe. The headstock design on it does allow the mandrel tube to slide thru the center and tighten with a pair of nuts. A do like that new tail stock design as it would allow retirement of the dreaded Jan Nut. In fact I see myself using it on both lathes. Jim

tom_k/mo · Post by **tom_k/mo** » Thu Dec 10, 2009 11:08 am

As Mark said, I guess I could still use this center with the Jam Nut... That wouldn't shorten the effective length of the mandrel any, it would still require all the additional spacers, but it WOULD allow me to turn with much less lateral pressure on the quill, and it wouldn't "bugger-up" the tip of my normal live center. I think I still may give it a try. Thanks for the inputs.

RobertTaylor · Post by **RobertTaylor** » Thu Dec 10, 2009 5:53 pm

a couple comments on this mandrel. if you push that center up against a flat surface such as the jamb nut you are most certain to get an out of round pen as there would be no lateral support for the mandrel unless it fits perfect in the hole. i believe their intent is for the bushings to fit inside the tapered part of the center and provide the neccesary support. i do not believe anyone ever bent their mandrel by overtightening the nut. the overtightening would be attempting to stretch the mandrel, not bend it. the threads would strip in either the nut or mandrel before it would stretch. i do believe that many pen mandrels are bent by over tightening the tailstock where the leverage is much greater. the tailstock center needs only to be snug enough to make the bearing revolve/spin.. imho this "new" center will cause more problems for penturners than it will solve.

iclark · Post by **iclark** » Fri Dec 11, 2009 12:26 am

Jim,

thank you for the further explanation.

Ivan

Ed in Tampa · Post by **Ed in Tampa** » Fri Dec 11, 2009 10:22 am

bettyt44720 wrote:a couple comments on this mandrel. if you push that center up against a flat surface such as the jamb nut you are most certain to get an out of round pen as there would be no lateral support for the mandrel unless it fits perfect in the hole. i believe their intent is for the bushings to fit inside the tapered part of the center and provide the neccesary support. i do not believe anyone ever bent their mandrel by overtightening the nut. the overtightening would be attempting to stretch the mandrel, not bend it. the threads would strip in either the nut or mandrel before it would stretch. i do believe that many pen mandrels are bent by over tightening the tailstock where the leverage is much greater. the tailstock center needs only to be snug enough to make the bearing revolve/spin.. imho this "new" center will cause more problems for penturners than it will solve.

I tend to agree I don't see how tightening a jam nut bends mandrel. Perhaps it is bent by during the process with heavy handed used of wrenches or whatever. But just the tightening process should not bent anything.

I also tend to agree mandrels are probably more likely to be bent by too much pressure on them from the tailstock. Turners get in habit of really hunkering down when they tighten stock between centers. Mainly to keep the stock from tearing out the drive center and not turning. If that same pressure is used on affixing the mandrel something is going to give.

I did a few pen turnings enough to understand the process (back when the whole concept started) At the time it was probably over simplified. Bore blanks, press in brass inserts, sand both ends flat and smooth, place on mandrel, turn. At the time end trimmers weren't invented, tube presses were non existant, and pen vises just hadn't happened. I don't remember any major problems. I would have thought being a raw rookie if there was major problems like bending the mandrel or something I would have found it. I have the nack for finding those hurdles.