My pen blanks are making googly-eyes at me

[Bob Daniel]

Hi folks... haven't been by for quite some time, but this one has me stumped at the moment, and I figured somebody here would instantly know where I went wrong...

I'm essentially a FIRST TIME TURNER, barring a couple of hours on school machines (once last year and once about 40 years ago !!) but I've been systematically preparing myself, both mentally and tool-wise.

In a nutshell, the problem is that after roughing down my first pair of pen blanks to reasonable cylinders, I stopped to inspect my progress and saw that the wood was well off-centre compared to the barrel tubes. I had to stop, as I was almost down to the metal on one side, with 1/8 inch left on the other side, all along the length of both tubes.

There's a photo and further description on my blog. If you could have a peek and maybe tell me where I've gone askew, I'd be very grateful.

Cheers.

rgdaniel.com/blog/2009/11-09-something-is-askew-with-my-woodturning/

[Barry Elder]

Is it possible that your headstock and tailstock are not aligned? That, along with tightening the tailstock too much, as mentioned before, could possibly destroy anything that you turn, penwise and otherwise.

[ROY DICK]

Bob,
Just my thoughts here.
It's either the eyeballing of the centers when drilling, or too much pressure
on the tail stock causing the mandrel to bend.
Good luck in the future and keep us posted on your progress.
Maybe even checking to see that the points of your head stock and tail stock line up.

Roy

[Phil St.Germain]

Are the tubes 7mm or are they larger and requiring a different stepped bushing? The barrels look to far off center to just be caused by over tightening of the mandrel. Drilling off center should have no impact. I regularly turn pen blanks that are poorly drilled(by myself).

[Bob Daniel]

Thanks for your thoughts, folks!

I DO remember the end of the mandrel kind of "springing" away from the tail stock by an inch or so when I loosened it, now that I think about it... so while I probably did overtighten it, in my ham-fisted newby eagerness, there may indeed be an alignment issue.

I'll look at it again today and let y'all know. Thanks for your replies!

[Aaron Wingert]

I made this same mistake on my first pens. The mandrel was bending under too much tailstock pressure, causing it to consistently wobble. The blanks were round, but offset from the center of the tubes.

Do the following:
Install the mandrel in the headstock taper. Move the tailstock close enough to touch, but barely, and lock it down. Start the lathe. Advance the live center using the tailstock handwheel until it engages the mandrel and starts spinning, and no more. Lock it down. Good to go.

I've also found that an adjustable mandrel lets me take up unnecessary length on the mandrel that I'd otherwise have to fill with spacers. Short mandrel = less vibration and deflection under pressure.

[Bob Daniel]

Looks like it may not have been my fault after all… there’s a significant wobble coming directly out of the headstock… a piece of dowel directly in the headstock (no chuck, no nuthin) wobbles all over the place, making about a 1-inch circle by the other end… had a long chat with “the guy at the place” and I’m taking the lathe in tomorrow for them to look at… it’s brand new, so it’s either defective or somehow askew from the factory in a way not easily adjusted or worked around…

http://www.rgdaniel.com/blog/wp-content/uploads/2009/11/IMG_1116-Googly-eyed-Pen-Barrels-300x300.jpg

[Ken Fitzgerald]

Bob,

I'd suggest that you use something with an appropriate morse taper to check it and not a dowel. I doubt if many people could get the dowel inserted evenly enough to accurately make that determination.

I can tell you from experience, the odds are in the favor of a bent mandrel or an overtightened mandrel causing the problem.

[Kyle Iwamoto]

What kind of pen mandrel do you have? If you have the cheap one, that holds the rod with a set screw in the MT adapter, do not bottom out the mandrel shaft in the MT adapter, much like not bottoming out a router bit. Give the mandrel somewhere to expand into. This in addition to less tailstock pressure......
If you're really going to get into pens, I'd suggest a better mandrel, if that is the one you have. I upgraded to teh PSI version. Much better than the cheap version. Went through 2 complete sets before I got the PSI. Kept getting those, and though that my mandrel was bent or the MT adapter was off.... Took me a while to figure out.

[Bob Daniel]

Thanks folks!!

I do have a good-quality chuck with a Morris taper inserted into the headstock, and this combination shows the wobble, with the mandrel as well as with a much stiffer dowel in the chuck... I was trying to determine if the chuck and/or taper were the problem, so I tested without them by inserting a larger-still dowel into the head stock, wedged it in just enough to confirm by slowly hand-turning that the wobble originates at the head stock.

Also, not sure I have a PSI mandrel... the kits are PSI, I remember... the mandrel looks like this:
http://www.jacquescoulombe.com/images/pkm-dl.jpg

Thanks for your comments! Much appreciated.

[David E Keller]

Bob,

I'm still not sure that I understand how you tested the spindle. Anything you jam in the morse taper is likely to wobble. Likewise, anything you mount in a chuck is likely to have some wobble until it's trued up. If there is significant runout in the spindle of the head stock, you should see it wobble with nothing in it or on it. I would try a couple of things. Measure from the ways to the bottom of the spindle and repeat that measurement three more times after rotating the spindle by hand. Also, you could turn the lathe on and lay a tool shaft over the spindle like you would if you were checking a rough out for round. It should bounce around if there's runout. There's probably a machinists tool for checking runout but I'm not a machinist and wouldn't know it if I had it in my hand. Let us know what you find out. Also, what kind of lathe? New or used?

[Bernie Weishapl]

Bob am I understanding right that you are chucking the mandrel in like a jacobs chuck??? If so I would try a mandrel with a MT #2 on the mandrel and see what happens. See if you get the wobble. I tried way back when I got my lathe to chuck up a piece of wood to make a finial and it wobbled so bad there was no way to turn it. Pressing a dowel into the headstock I don't think is going to tell you much as Ken said. You might try this collet chuck. I have one and it will grip a pen mandrel, bottle stoppers and wood with a tenon for turning like finials. This is the one I have and it works well for PSI. Of course if your lathe is bigger than 1 X 8 it won't work.

http://www.pennstateind.com/store/LCDOWEL.html?mybuyscid=4193505631

Have your put a drive center in your headstock and a livecenter in your tailstock? Bring them up to within a 1/16" of each others points. Turn your headstock spindle by hand. If it doesn't move (wobble) and the points stay on line with each other I would say that the lathe is fine. If the headstock spindle drive center tip as you turn it makes a circle around the tip of the livecenter in the tailstock then you could have a problem.

[Bob Daniel]

Thanks for your answer... you're right, it wasn't probably good machinist practice, I was just trying to narrow things down...

I took my mandrel complete with my blanks in to the store today, mounted it on their chuck in the same lathe I have, in the same way as at home, and no problem, trued it right up...

Back home, same setup in my chuck, wobble city...

So tomorrow the lathe goes with me to the store, and we'll see what happens...

It's a King Canada 10x16 (http://www.kingcanada.com/Products.htm?CD=29&ID=2385) by the way...

http://www.kingcanada.com/Files_LR/KWL-1016C_HR.jpg

[Joe Melton]

The point of the live/dead center mounted in the tailstock must align with the centerline of the spindle. Just having the tailstock center touch a center mounted in the headstock means nothing. If the centerline of the spindle is off, the end of the mandrel at the tailstock end will swing in a circle, and constraining it with a live or dead center just causes it to deform as it rotates.
Mount your mandrel first. Bring an end of your toolrest over so it is almost touching the free end of the mandrel. Turn the handwheel slowly with your hand and observe the gap between the mandrel and the tool rest. You will quickly get an idea of whether the mandrel is turning true.
Failing this test doesn't necessarily mean the spindle centerline needs adjusting, though. Remember that the mandrels we use are mass produced and cheap. Expecting perfection from one is a pipe dream.
I've bought all kinds of mandrels, including the ones that fit in the Beall collets, and turn on a Oneway lathe. I have never had a pen mandrel turn absolutely true.
To accomodate for this, I do the final sanding with 220 grit, and then loosen the nut and, holding the bushings in place, rotate the pen blank 180 degrees. I then sand again. This helps to account for lack of perfection of the mandrel in its rotation. After I turn the pan blank, and before I resand, I can feel, with my fingernail, that the pen blank is not flush with the bushing all around. Turning the blank 180 degrees works well enough for me. I then sand with 400 paper without turning the pen blank in the bushings again, and then polish.
Hope this makes sense to you.

[Bob Daniel]

Thanks Joe... not sure I followed all that... I'm gonna see what they say in the store tomorrow, and go from there... SOMETHING in my setup is not right, maybe it's me, maybe it's one piece of machinery or another, I don't know. I just want to turn some pens, and it's not working... shouldn't be this hard or this esoteric...

[Bob Daniel]

Well, the good folks at Welbeck Sawmill (http://www.welbecksawmill.com/index.html)came through for me again. Turns out I was correct in saying that the problem was with the head stock itself. The machining inside the head stock, where you insert the Morris taper, must be off true, because every taper and chuck combo we put in there turned wobbly on my lathe, and fine on another lathe (same model and everything). So they sent me home with the other lathe -- which is the same vintage as mine, he just had it out to teach a couple of classes. Now I can try some of this concentric turning I've heard so much about... ;)