I need some help here, I am doing something wrong and I am not sure what I need to correct. I recently turned some Patriot pens from Craft Supplies, the fit of the hardware is great, but I have a problem with the hardware being flush to the wood on one side of the pen barrel, but offset on the opposite edge of the same diameter of the barrel.
I am using the same pen mandrel (Lee Valley) I use for all my pens, it�s 7mm, so are these bushings (Craft Supplies)�I am also using firm but not hard pressure from my tail stock on the end of the mandrel.
it sounds like your mandrel may be out of round. You can check it in several ways. The quickest and easiest I think is to start the lathe with the mandrel in place, but no bushings. Then, take a pencil held on the toolrest, and VERY lightly touch it to the mandrel. Turn the lathe off. If there is only a part of the mandrel with a pencil line on it, then the mandrel is not running true. The less line on the mandrel, the more out of square it is. To correct, turn the side of the mandrel without the pencil line on it towards the toolrest, put your thumbs under the toolrest, and pull the mandrel towards the toolrest. Try this on several places on the mandrel. You can generally feel if the mandrel is not running true by simply feeling it (without any bushings installed), and you should feel some vibration if it's not running true.
It could also do this if there is 'slop' in your bushings (if they don't fit the mandrel tightly, and wiggle at all.) This is probably not the issue, but it's possible nonetheless.
The mandrel itself could be the problem, and needs to be checked as mentioned above.
Another reason is the ends of the barrel not being square. This can put a bow in the mandrel when the nut is tightened. This might not be noticed if the mandrel springs back to shape after making the pen.
Make sure the wood barrel is slightly longer than the tube. Insert the tube so it is centered in the wood. Then square the ends TO THE TUBE. The reason is that the hole might not be running straight in the wood. The best way to do this is with a barrel trimmer.
Wood thickness around the tube after turning is a clear indication that there is bowing. The barrel end near the headstock is more centered.
Thanks for the response. I needed to put spacers on the mandrel to take up the spacing for the single tube I was turning. I was turning at the tail stock end, I am guessing as you have said, if there was any bowing that it would be more pronounced there....great observation.
>Absolutely! It compounds any bowing already there whether the mandrel is not straight, or it is being bent by the nut when the barrels are not square.
Glad you mentioned this, because first of all I don't like using the pointed live center with the mandrels. I use a home-made live center. It has a cup center and also is spring loaded. It has a ball bearing also. The pic shows it in two parts, the Morse taper screws into the coupler.
>Now that's a neat idea. Using a pointed center has always bothered me a bit but I'd never thought of spring loading a small cup center. I may have to give it a go myself. Thanks
>I am looking into a possible easy solution to make a better version of this "mandrel center" based on a live center that is readily available and cheap.
The cup center in the pic slides inside a bearing with a 1/4" bore. The spring rides on a nylon washer against the center of the bearing.
If there is enough interest, I will post construction details for the new and improved model. Cost for all the parts will probably be less than $20 including the live center.
By the way, I have made mandrels from 1/4" threaded rod. It is the right diameter, right around .245. Size D drill rod is also the right size.
>A properly fitting Morse taper and a well centered bearing cost a lot to custom machine.
So I am looking at commercially available live centers that can be easily modified to take a spring loaded cup center.
Right now I am looking at the live center from Woodcraft, item # 141060. I understand the cup comes off, and the point is replaceable. At $15. it will probably take another couple bucks and a few minutes to modify it.
I will pick up this item over the weekend, and keep you posted of my progress.
Since you taught me how to turn pens way back when, I seem to remember that you turn the nib end towards the tailstock. After I got home and started making pens for myself I quickly found out how fast a mandrel can destroy the tip of a live center. I�ve broken the tips off some and just plane wore others out of round. You can easily check to see if you have worn the tip of your live center out of round by removing it from the tailstock and putting it in the headstock. Set the lathe for slow speed, turn it on, and watch the tip for run out. I haven�t had much success at trying to file the tip dead center again. It finally dawned on me that the live centers I was using had too much mass. If I tightened the tailstock up to much it would bow the mandrel a bit. And if it was too loose when I turned on the lathe there wasn�t enough friction to bring the center up to speed fast enough. So every time I turned on the lathe it wore the tip even more and pretty soon it was out of round again and screwed up my pen barrel. Wanting to save some cash I finally went down to the Grizzly store to buy a cheaper center. Turns out theirs is half the mass so that was good. Then I filed the sharp tip of it down a bit to make a blunt end for a better fit. It has worked well for me ever since.
