I use John's for most of my pens and swear by them. However, the TBC is often questioned as being too expensive along the lines of "I can't afford that". And it comes from people looking at custom bushings.
Also, almost every time I see TBC, I see 60° in the same sentence, which also gives the wrong impression. I don't see people telling new turners "Welcome, you are new, get your 60° LC for your mandrel." A 60° LC IS a requirement for a mandrel, But it is NOT an absolute requirement to go TBC with regular bushings.
TBC is like pen turning itself. You can do it on a Nova or Powermatic or Jet, or Rikon or PSI and even a Drill Press. It is not relegated to one end of the "cost" spectrum.
When the focus of TBC talk is ONLY on the high end, fewer people are going to try it because of "cost" and complication perception, when in fact it is not. We will get tons of continuous questions about OOR & OC and when TBC is recommended, we get the "I can't afford to go to TBC yet" answer.
TBC can be cheaper than Mandrels to get started, and TBC offers much better precision, fit and finish. The difference with TBC is that TBC users can climb the expense ladder as they need and get finer bushings.
I did mislead on one item in my post. For that, I apologize to you and to John. John addressed that issue. There is less contact space when using a 60° (or dead center such as mine,) on standard bushings and I think that standard bushings will benefit from the chamfer as originally asked - IF chamfering can be done correctly. AS John said, 60° is the industry standard for the metal machining. However this does not apply to most wood lathes and their stock centers. A few people have made dead center drives from wood to use on standard bushings. I don't want people to think that as an absolute . . that "60°" is a necessity.
Concerning Standard bushings: Most of us who have been TBC for the past 2 to 3 years started with standard bushings and had a great improvement with just that alone. Early on, I never had a problem and I don't think that anyone else die either when using standard mandrel bushings for TBC - except for when the standard bushings that were drilled OC to begin with. IIRC, that is what gave birth to custom bushings, not the small shoulder connections. The chamfer of John's bushings is a bonus in that it stops the "digging in" ring on steel dead centers - that standard bushing can cause over time and with slippage.
That said, Johns bushings are the BMW/Porche of bushings and I don't mean the glitzy part but the accuracy and finely machined parts. AS I said, I use them but they are not necessary to get started. Once you do get started, you will want the finest and that would be John's.
I do have some standard bushings that are OC by .004 and that is just enough to make me want to through them away but too close to accurate to let go. You will not find that with John's. His is dead on.
Bottom line on TBC, the cost is far more flexible for the accuracy that you get than with mandrels. TBC - it can be cheaper and it can be more expensive, but either way, it is more accurate overall.
