Atlas Forward/Reverse Switch

The Atlas machines all have threaded spindles. So, unless your chuck is one of the more expensive ones with the added split locking sleeve, do NOT try to machine in reverse. But on the other hand, I have had an Atlas lathe with a reversable motor and switch since 1981. And I have never had a chuck or face plate come loose simply by reversing the motor.
 
wa5cab said:
The Atlas machines all have threaded spindles. So, unless your chuck is one of the more expensive ones with the added split locking sleeve, do NOT try to machine in reverse. But on the other hand, I have had an Atlas lathe with a reversable motor and switch since 1981. And I have never had a chuck or face plate come loose simply by reversing the motor.
Click to expand...

I recently made up a draw bar for holding my ER-32 MT-3 . . . ???. . . thingy.

High on my list is to make a part that will fit inside the chuck, below the jaws, that will allow the draw bar to hold the chuck in reverse.

I have the reverse switch, which is tied to the VFD that handles the "forward to reverse without stopping" problem, but haven't used it because the chuck isn't locked. I tried using it for threading once, so that I wouldn't have to bother with the threading dial, but that destroyed my carbide threading insert.
 
You need to re-read the instructions for cutting metric threads on a lathe with an inch lead screw. You are supposed to stop the spindle and back the cross slide out before re-starting the motor in reverse. All lathes have some backlash in the half nuts, even if the machine and all components are brand new. Even if cutting inch threads. You are supposed to cycle the cross feed between one setting for cutting and another setting for returning the carriage to the start position. DOC is set and increased only by the compound feed.
 
Seems to be a lot of 'foo fah rah' about doing a conversion to DC. Which is fine if that's what you decide to do. All of my stuff has induction motors because I've worked on DC motors in years past and don't want fool with them any more. Just being old and obstinate. . .

If you are mounting a single phase motor at 120 volts, the basic premise is there are two windings, a start and a run. To reverse the motor, you swap the relationship between the start and run. The usual practice is to reverse the start winding, but is not an absolute. There are a half dozen or better switches so I can't give terminal numbers, nor can I specify motor leads. Together, you probably have half a hundred different combinations. Then there are 240 volt connections, which add another dozen or so combinations. All, well most are doable, the biggest issue is knowing which one to do.

Most switches will have six terminals, three sets of contacts. Most of the time, the lower of the three contacts is basically an on-off switch, switching on in either direction. The other two contacts, 4 terminals, make up a reversing switch. Connect the run winding through the on-off contact. Connect the start winding through the reversing contacts. I can't be more specific without writing a book, well at least several pages. There are too many variables, this will have to do. And I'm not sure where some of my drawings are after crashing last year. But this is the basic idea, you dig out the terminals.

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That's my aim eventually, to write a few pages on how to connect any reversing switch with any motor. One of these days...
Easier said than done :)
-M
 
Realizing up front that you are not dealing with a Sq.D reversing switch, I include the documentation more as a guide for the different types of motors, with the switching terminals as secondary. The circuits shown will be, of one sort or another, what is used. The terminal definations, the terminal numbers will vary from switch to switch. As will the physical location of the contacts. But at the bottom line, this is what a reversing switch does. There are different diagrams depending on whether the line cord comes in to the switch or the motor. My personal preference is to bring the line cord into the motor and run a six conductor cable to the switch. But that's just my personal preference, it keeps several points clear(er). And keeps down the number of wires in the switch enclosure, which is crowded enough as it is.

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I found this wiring info for the Furnas L143 in another post from about 2014 and edited it.

The six terminals on the switch should be called L1, L2, 1, 2, 3, 4.

The motors "RUN" winding or windings if the motor runs on both 120 and 240 VAC connect to terminals 2 and 4. The "START" winding is fed from terminals 1 and 3. If the motor rotation does not agree with the switch markings, reverse the connections to the start winding on 1 and 3.

The remaining two terminals on the switch should be labeled L1 and L2. Connect the Line and Neutral (if 120 VAC) or the two Line wires (if 240 VAC) from the line cord to these. Connect the Ground wire (should be green in all cases) from the line cord to any available screw or bolt that is electrically connected to the switch body, lathe frame, headstock, etc.
 
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