View Full Version : Found an interesting feature on my lathe

03-12-2009, 09:52 PM
My CamTak lathe has a lever for forward/stop/reverse on the carriage like many lathes that start and stop the motor rather than a clutch.

I was drilling some SS flanges and grabbed the lever and moved it back out of the detent and accidently lifted it instead of going down to stop the motor. Well, it suddenly reversed the spindle. Man, that sure surprised me. So I operated it several more times and it looks like I have an instant reverse feature for power tapping or any time I need to reverse quickly. I sure wouldn't do it running faster than 300 rpm but it sure works smooth at that speed and even better slower. I don't like to reverse motors fast like that but it may come in handy sometime.

03-12-2009, 10:45 PM
I assume you are talking about a 3 phase motor?

Most any 3ph motor will do that, it's often referred to as "Plug-Reverse" and other colorful names. But you spike the current, so make sure the wiring can handle it.

Also handy for metric threading to a shoulder when you can't pop the half-nuts, but I prefer the brake.

03-12-2009, 11:25 PM
Yes, it's 3 phase but I would not use it for metric threads because of the backlash in the gears and carriage. I am sure the spindle would make several turns before the carriage started back and that would bugger the threads. If I cut metric threads I stop the spindle with the foot brake and back the tool out then reverse the spindle.

The instant reverse feature may work for power tapping with the tailstock in through holes. The reverse feature is not even mentioned in the manual so I don't have a clue as to what they intended it for.

03-12-2009, 11:36 PM
seems just like any real lathe I had to make a living with would do.

3 phase has nothing to do with it. single phase 220 VAC lathes have reverses on the stick too. Even my runt 110 VAC smithy 1220 Midas has reverse but its a switch on the headstock.

03-12-2009, 11:47 PM
I always used the normal way of moving the lever toward the tailstock and lift the lever for forward and then move it down to neutral and then move the lever toward the tailstock and push it down for reverse. That's the way similar lathes in the job shops I worked in operated but none of them had the second up position on them that I know of.

But this time I was running the lathe in forward with the lever up and I accidently lifted the lever instead of pushing it down. When I did that the spindle reversed instantly. I tried it several times and it works perfectly. I have had this lathe for about 14 years now.

It does not have that feature in the reverse position.

03-13-2009, 04:26 AM
I think it's a rare 1ph that will instant reverse. I've heard of 1ph that would do this, but no real knowledge other than none of my 1ph stuff has ever supported it.

On the threading, I agree. But my lathe, particularly with a heavy chuck, takes some spin down time with the brake. You have to estimate and guess when to trigger, then feather it into the runout depending on how much room there is. With the power reverse, even with a heavy load, I can pretty much instantly stop it and then go directly to off while on the brake. But yeah, pretty much generally always use the brake, and always crank out before the return.

But lots of folks use "plug reverse" to power tap on both a mill and lathe with tailstock/turret mount.

Just realized I missed the part about not actually going to reverse position. That's interesting, never seen or heard of that. I've seen the switch mechanism that controls this on my lathe, and can't imagine how that would work in my lathe. I wonder if it's just a case of a cam limit out of adjustment letting the reverse switch close when you go past what should be the stop? <shrug>

03-13-2009, 11:56 AM
None of my single phase equipment is instant reverse. All operate on either cap start or split phase start technology. Both those technologies have centrifical swithes to disconnect the start circuit after the motor reaches roughly 1/3 of operating speed. Moving the switch from forward to reverse does not reverse the direction of rotation, but does continue to supply power to the motor = continued running. The start circuit's function can be replaced by spinning the motor shaft after power is applied if the cent switch goes or the start circuit fails... bump starting... One thata few times too :rolleyes:

03-13-2009, 12:20 PM
The next time I pull the quick change box cover I am going to look at the switch arrangement to see what is happening. I am puzzled by no mention of it in the manual and wonder if something is out of adjustment but since it drops forward and picks up reverse so well I don't think it's an out of adjustment thing. I just wish I knew what the factory intended it's use for.

I don't like to instantly reverse the spindle when power tapping because it can break taps or tear up threads. I like to coast down then reverse.

The lathe was built in 1984 in Tiawan and is now an orphan. The factory makes industrial CNC machines now and don't support the older stuff.

J. Randall
03-13-2009, 10:16 PM
Some older 1 phase lathes had instant reverse, runs in my mind it was some of the small SouthBends . Without doing a search I think the motor was made by G.E. Most will just keep on going in the same direction if not allowed to spin down.