Lathe sweet spot? I don't think so.

[Frank Fusco]

I'm having a bit of a dispute with a supplier of pen turning supplies. I recenlty bought a new mandrel with a #2 MT arbor that I believe is defective. But, first, some background.
My lathe is a Grizzly G1027Z. It runs smoothly with no wiggle-waggle, bounce or other run-outs or nasties. When the tailstock with live center is brought up to the spur, the two points meet perfectly. My turnings are round, not oval. The new mandrel was bought as a supplement to my old one. The old one has been used for countless pens and duck calls without a problem. When in the lathe the live center point mates perfectly with the dimple in the end of the mandrel.
OK, now: The new one, also a #2MT arbor did not line up. The end of the mandrel was 3/16" to 1/4" off from the point of the live center. When forced to mate I tried turning a pen. The blanks wobbled and bounced wildly and was impossible to turn.
A complaint to the supplier brought the advice that I should look for my lathe's "sweet spot". Meaning, mount the mandrel then, by hand, turn the spindle until the off-center end of the mandrel rod lined up, or came close, to the tip of the live center. Or, with the arbor loose in the spindle, turn the unit until it mated with the tailstock. He said this was necessary on all lathes. Normally, he is reputed to be a knowledgable, level-headed guy. But I discounted this 'advice' as pure nonsense. I believe a lathe should be true without off-center anythings or non-concentricities. If it doesn't line up, something is wrong. IMHO.
He refused to exchange the item but did refund claiming he believed I would never be satisfied with anything.
I ordered a new mandrel, of a different make, and it lines up perfectly, as does my old one. I think if it's right, it's right. If it's off-center, it's wrong.
Now, this guy has many years more turning experience than I do and is well reputed for his expertise. So, I am baffled by this disagreement.
What say the jury?

[Chuck Saunders]

If it is off center it is bad, period.
Chuck

[Doug Thompson]

You are right there is no sweet spot on a spindle. If he's local take it back and let him try. If not call him again. You might have caught him on a bad day.

Let us know

[Bernie Weishapl]

Frank I had the same problem with one I bought from Woodcraft. I took it back and they exchanged it with no problems. The one you had has a problem and he should have acknowledged that. If your centers line up perfect then the mandrel should do the same.

[Raymond Overman]

I have had the instance where I had to "adjust" my mandrel due to my heavy handed sanding technique. I had a slight bow in the middle of the mandrel which caused run out at the center bushing of my pens. After figuring out which way it was bowed I was able to correct the problem and take out the bow. I've also seen this occur when you over-tighten the brass nut on the end of the mandrel and cause a slight bow. I've also had problems where sawdust or other dirt/grime caused the mandrel to be off at the headstock enough that it caused problems.

That being said, you probably checked the headstock and tailstock morse tapers for debris. You would have had problems with your old mandrel if there was any trash there. A new mandrel out of the box shouldn't need to be adjusted but I probably would have tried prior to going through the hassle of sending it back. Even a slight bow creates an eccentric pen. The fit and finish should be spot on.

Obviously if you replaced it and it works properly, the mandrel was the culprit, not the lathe.

[Ellen Benkin]

You're right. He's wrong. You have two mandrels that work and his that doesn't. End of story.

[Jim Becker]

What Ellen said. The mandrel obviously wasn't mounted "square" in the MT#2...and the MT eliminates any "sweet spot" theory, anyway, just due to its nature.

BTW, be very careful with pen mandrels that you do not engage the tail stock/live center too tightly...you can deform the mandrel with any kind of pressure and that makes for both wobbly turning and poor results, not to mention the need to replace the bent mandrel. ;)

[Frank Fusco]

Thank you, ye of the jury. I hate to call a guy wrong unless I have confirmation. That 'sweet spot' notion seemed like baloney to me. A lathe that isn't true is scrap iron.

[Jim Becker]

That 'sweet spot' notion seemed like baloney to me.

Very well aged baloney, Frank...and a different color than it original was!

[Wes Bischel]

Very well aged baloney, Frank...and a different color than it original was!
That wouldn't be Lebanon Bologna would it?:D

Wes

Oh, and it's a PA thing.

[Corey Hallagan]

Hmmm... I don't even have to guess who you are talking about :) If you complain in a forum everyone will come out singing the company song.. god I hate that. All of my PSI and Berea's mandrells originally met at the centers. I have a psi one that I believe I tightened a little too much and it no longer does but I turn cigars pens on that one and they are large enough if they aren't perfectly round I will never know it. Everything I read says they should line up at the centers, if they don't then there is a problem somewhere and it doesn't sound like it's the lathe!
Corey

[Curtis O. Seebeck]

Could someone PM me or post the initials of the company in question. I have my ideas based on previous experience but would like to confirm them so I know to stay away. Thanks.

[Jim Becker]

I'm not sure I understand the reluctance to post the source of this, umm...creative theory...

[Rob Bourgeois]

post it before I go buy another mandle...( selling my with my lathe--getting a differnt type)