Pen Mandrel's and Bushings

[fjimp]

Earlier today a friend asked me a question that seems worthy of answering here. I remember a time when I would have asked the same question.

"If I get a mandrel to do 7mm slimline pens, do I have to buy another one to do 10mm pens? Or are the inside diameters the same. Just the out cirumferance changes? Is that correct?"

My answer; Yes all of the Mandrels I have purchased were for the 7mm bushing set. Yes the 8mm and 10mm bushing sets have the same ID measurement and work well on the standard 7mm mandrels.

Note: I make it a habit to keep at least one extra set of Bushings on hand for every pen set type or diameter of bushing configuration. I also keep an extra shaft replacement shaft on hand they do at some point become bent and there is no reason to replace the entire mandrel set. Okay not all mandrel set have a replacement available. I buy the PSI Maxi Mandrel sets. Jim

[RobertTaylor]

for the most part you are correct. the mandrels are 1/4" and the bushings have 1/4" holes regardless of the kit. these are called "A" mandrels and/or bushings. however there are still a few "B" mandrels out there for some of the larger kits. arizona silhoutteand berea still list a "B: mandrels and bushings. the "B" mandrel is about 5/16" in diameter so obviously the bushings are not not interchangeable. in the photo below is an "A" and "B" mandrel. the A on top, B on the bottom.

[nomoman]

"A" and "B" mandrel. the A on top, B on the bottom.

What about "O"?
Jim, you said "I buy the PSI Maxi Mandrel sets". Do you also have the PSI Shopsmith mandrel? Does the Maxi fit the SS?
I am confused.