Lathe continues in forward even after selecting reverse

[John Hasler]

It looks like there is a way to do this with a single phase motor. This also may be a special instant reversing motor diagram, I'm not sure.

I don't see that this circuit is going to work. When you throw the switch from forward over to reverse it appears to me that you end up with both windings energized and the capacitor out of the circuit. This will result in the motor continuing to run in the same direction while drawing more current.

This diagram looks to be the same electrically, but is a bit more clear and easier to read.

I think this circuit will work, but it isn't the same as the other.

The motor is special at least in that it has a double-throw centrifugal switch.

 

[ddmunroe]

I've used the term "instant reverse required during threading. This is being differently interpreted to how I meaning it in actual use.

This method of using your lathe to cut threads is carried out all the time. (does anyone else know this is common practise ?)
BUT
It really is a matter of some coasting to where you want to reverse, "then reversing.
In this case most of the inertial loads are reduced therefore not breaching any structural limits of lathe parts.

Lots of comments have been made about damaging the machine. I'm starting to understand that you have the picture of some one willy nilly smashing their machine in reverse at any speed thinking this is ok.
Describing "it's like banging a car in reverse while moving forward is totally off topic :banghead:
So really what's needed if you have a capacitor motor is a method of circuit disconnection at the precise point stopping, then reversing.
This has been described previously by the astute.
In future I will be slowly gravitating toward VFD, brushless motors and controllers. Look forward to sharing my results.
dd

 

[UncleRuss]

Mr. Hasler,

Very good point in your last post. Yes the motor will continue to run in the same direction if switched too rapidly, not allowing the centrifugal switch to close. Also good eye on picking up the fact a two pole centrifugal switch is being represented in the second drawing and that being the magic of the second diagram. Going to have to slow down as I missed both points in reading the first time through.

May I ask what is the matter with machining a groove at the end of where the thread is to stop as is the old practice. Or as I do quite often is to stop the lathe anywhere near the end of the thread and using a die by hand to finish off. That is of course if you have the proper die. I rather like the looks of the thread finishing in a groove. Looks more professional to me.

Instant reverse is not very good for most anything I know of
Carry on Gentlemen, always more then one way to skin a cat. Now pile up that SWARF!