manual turret lathes: the part I don't get (multitude of spindle start/stops)

[DR]

My 9X20 Jet has a clutch arrangement that allows multiple stops without problems. It is one of the reasons I kept it when I found my Logan. It irritates me to turn the lathe off to mike something. The air conditioning clutch idea intrigues me, though. Bob.

This post reminds me of probably the dumbest idea I've ever seen in HSM mag, a cover story no less. This might have been 15 years or more ago.

The article proposed a belt slacking mechanism for small lathes where you could slack the belt while keeping the motor running to change/measure/whatever on workpieces.

Very dangerous since there was no brake on the spindle, the belt would have a tendency to grab and rotate the spindle.

When the article came out I called the editor and explained why this was not a good idea at all. He didn't understand my concerns.

The mag came out every two months and it took 4 or 6 months for the editor to finally print somewhat of a retraction of the article explaining the danger of the idea.

On edit: Just to be clarify, I didn't mean to imply in any way anything at all was dumb about Bob's post. Only that the subject reminded of the HSM mag blunder.

[Peter.]

How was that done?

I would guess that they would turn the tap faster than the part to reverse it out?

[Arthur.Marks]

That was going to be my guess as well. A live spindle (it wouldn't surprise me one of those could run faster than even a typical, Swiss high-speed main spindle). For example, I could see a small precision live spindle having capabilities in the 45-50,000rpm range. Furthermore, this follows the general gist of the discussion: to accomplish the tap reversal, it would require a near instant start. Otherwise the tap depth would be hard to hold any tolerance on. Are we right??

[DR]

Yes, you and Peter are correct, the tap is motor driven with a two speed motor, one speed in the other out.

Now of you two guys will forward your mailing addresses to me, I'll send each of you a check for $500 as co-winners of this teaser. The checks will go out at my earliest "convenience".

[Arthur.Marks]

I trust these checks will be payable in Certified Gold Dubloons? I don't deserve it because I have a follow-up question: Why does the tap need a motor to cut as well as reverse? Wait--while writing this I think I answered my own question. Without rotating up to a speed much closer to the main spindle, the tap's SFM would be outrageous. Hence, broken tap. I'll tell you, those swiss lathes are really fun to watch, but they must be a complete bear to program. I was mesmerized by them last time I visited IMTS. Multiple live tools, front and rear part spindles on the same machine, integral moving guide bushings, and on and on... The initial programs must get run veeeeeery sloooooowly a few times to debug. A crash on one of those things would be spectacular!!