'Universal' pen mandrels -help!?

[Neil Dyball]

Hi, I'm looking for some advice from the more experienced/intelligent pen turners than myself!

I've used a standard mandrel and various sets of bushings in the past, i.e. specific bushings for specific pen kits.

I was going to buy some pen kits from a particular supplier (who shall remain nameless) and asked about bushings. They said "we only sell the Universal mandrel which is suitable for all our kits".

I understand (I think) that these kits include cones to support larger diameter tubes than the mandrel itself, however, I don't understand how you can gauge the final external diameter of the finished pen blank if you don't have a correctly sized bushing to work to. :?

Can someone enlighten me please?

Many thanks,

Neil.

 

[CHJ]

Not seen one myself, but if it is a simple cone on each end then you are correct, I would think it would be very difficult to judge diameter of the turned barrel, even a tenth of a mm can look out of place with some kits.

If however they are stepped cones then maybe they have guide potential although with the variety of pen kit diameters I can't see how you could hope to make a stepped cone to accommodate the tube bore differences and the external size guide for them all.

 

[Neil Dyball]

My thoughts exactly!

 

[oddsocks]

Neil,
I normally use the correct sized bushes as it makes life easier, but sometimes I have used either the cones (or in my opinion better) a light pull drive in headstock and revolving tail centre. To get the exact size I use a digital caliper set to 0.2mm bigger than I need. Once turned at this size the caliper is reset to the finished size (against the pen kit) and then abrasive used to get it perfect - be careful below 400grit as it reduces diameter quickly!

With the lightpull setup you can also quickly remove the blank and turn it around if needed. Pretty useful for keyrings as well as the end caps do not appear to match any bush that I have