TBC Bushings

[montmill]

I recently posted a question about the washer size on this mandrel: https://www.exoticblanks.com/turn-between-centers-mandrel-system-shopsmith.html

I'm curious what's the difference between numerous sets of TBC bushings and using this with the bushings I know have on hand?

 

[Dehn0045]

My understanding is the PSI TBC mandrel system is designed to be used with standard bushings. It is basically like a more precise and more rigid mandrel. Typically "TBC bushings" have a 60 degree taper such that they fit between a 60 deg dead center and a 60 deg live center. When tightened down firmly the extra surface of the taper provides enough friction such that the blank can be driven by the dead center. However, when turning solid metals the friction alone is not enough, but for most penturning applications (including metal segments) it works fine.

Edit: note that often times "TBC bushings" do not have a thru-hole, so they can only be used between centers, my TBC bushings are this way. Also, you can use standard bushings between centers, but it will cut grooves in your centers and will not be quite as rigid or precise.

 

[KenB259]

I can't tell you the differences, but I know the mandrel system you linked gets a lot of bad press. I can tell you I use that system on every pen I make. It works extremely well for me, been using it a couple years now.My pet peeve is you will get bad reviews from someone who has never used it. I give it a thumbs up for what it's worth and I'll let my pens speak for the end result. I'm very picky and if I didn't get good results, I wouldn't use it.

 

[mg_dreyer]

The washers are suggested to keep the bushing from sticking to the mandrel. The biggest issue with this system is if the bushing have a burr they get stuck. I use 1/4" nylon washers on each part to come the small gap.

I am thinking this is what you are looking for. I have a full youtube video on this mandrel if interested. Search "10 Minutes To Better Penmaking" and look for the out of round video.

 

[montmill]

Thank you Mark, I watched the video. Great explanation.