Newbie, back gear questions

If it retuns from leo it will undoubtedly fall in the same place as various gun springs, knife springs and an infinite number of motor parts.
Large reward for the finder of that location!
 
For what it’s worth, I recently re-wired the SB lathe motor so I could run it in forward or reverse. I was cutting metric threads and used reverse to power return the apron after each pass. That’s how I kept the half nut engaged during the whole threading operation. The reverse capability was handy for that, but that’s about it.


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Theron751 said:
If it retuns from leo it will undoubtedly fall in the same place as various gun springs, knife springs and an infinite number of motor parts.
Large reward for the finder of that location!
Click to expand...
Bottom of the Marianas Trench. We know where but haven't the wherewithal to get there. A trolling magnet keeps getting lost on the long leader.
Lastwagen said:
For what it’s worth, I recently re-wired the SB lathe motor so I could run it in forward or reverse. I was cutting metric threads and used reverse to power return the apron after each pass. That’s how I kept the half nut engaged during the whole threading operation. The reverse capability was handy for that, but that’s about it.
Click to expand...
I have an MFC with the motor reversable. There are times work is mounted on an angle plate and milling cutters attacked through the MT2 spindle. As it works out, mandrel cutters in automatic feed run better one way and milling cutters run the other. I consider a reversible motor to be an absolute necessity.

My Atlas/Craftsman 12X36 is reversible, like the above. The biggest reason is threading, but there are other uses as well.

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Are there any other issues with the gears or any internals using a reversable motor? I am just starting out and probably won't need that for awhile but can be collecting parts in the meantime.
 
The most obvious is the drawbar running backwards(loosening) Any other is unknown from my perspective. I haven't encountered any problem yet, but my machine time is fairly low. I will say, as an aside, that most of my run time is in back gear. Mostly because I don't know what I'm doing.

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The danger of running the spindle in reverse is that all of the Atlas machines have a threaded spindle. So if the torque required to turn the spindle is high enough, the spindle chuck will unscrew itself and fall onto the bed. So with a threaded spindle, you never perform any cutting operation in reverse. However, if you properly seated the chuck against the register or shoulder at the back end of the spindle threads, it will take significant torque to break the threads loose in order to remove it. So after 40 years of routinely engaging reverse whenever I needed to, I have never had a chuck start to un-screw itself.

The two operations that routinely require running the motor in reverse are OD grinding with a tool post grinder and cutting a metric thread. In the latter operation, you MUST remember to back the cutter out clear of the work piece before starting the motor in reverse.
 
My MFC now has a proper drum switch. When I first set it up, I had a DPDT (double pole double throw) toggle switch wired into the start winding. A drum switch is essentially the same thing, but with a sort of interlocking control. The original switch was wired with a piece of 4 conductor "SO" cord out to the front of the machine.

Even with the drum switch, on a single phase motor, the motor must come to zero speed before reversing. I am familiar with that sort of control anyway, so the toggle switch was no big deal to me. The only adder was the third contact on the drum so I only have 1 switch.

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FWIW, all of the original mills came with a two position bat-handle toggle switch, not a drum switch. I am not sure as to whether it was a SPST or a DPST. The latter would be safer if you do not know where the Neutral and hot wires are or are using a 2-pin line cord plug. However, there is really no excuse for either case.
 
The only situation where a DPDT switch would be in the LINE would be if the motor was 3 phase. And then only as a directional, not a line switch. In any single phase case, the DPDT switch would not be in the line cord at all. It reverses just the start winding, using a separate ON/OFF switch. In answer to the above, it would not be a SPST, single pole switch unless controlling a relay or starter. My use of the drum switch is my own modification to allow use the third contact set as an ON/OFF switch.

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Actually, although it wouldn't be as safe to use, an adequately sized SPST switch would work OK as a direct motor start switch. It just wouldn't be quite as safe as a DPST, especially in an era when 2-pole line plugs were the rule rather than the exception.
 
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