Craftsman/Atlas 618 Reverse

[miner49r]

It looks like I am needing to cut some metric threads and will be required to run the lathe in reverse to return the carriage to the start position. The motor is a GE 1/2Hp 1725rpm with capacitor start. Under the cover plate shows the wiring for reverse rotation. So far so good.
Looking at my options, it appears that most people are using barrel switches. Why couldn't I just use a 20amp SPDT-CO momentary/contained toggle switch?
I am thinking that using the contained side for forward rotation and the momentary side for reverse along with the original on/off switch would keep the lathe from accidentally starting in reverse unless the toggle is deliberately held down.

Your thoughts?
Alan

 

[gbritnell]

Hi Alan,
I have a 1/3rd horse induction motor on my 618. I have it wired for reverse. I used a DPDT mounted on a little bracket on the motor. It works well.
gbritnell

 

[rhankey]

Perhaps I am wrong, but I thought you needed a 3ph motor to be changing between forward/reverse while the motor is spinning. My understanding is that if you attempt to change between forward/reverse on a single phase motor while it is running can or will result in the motor carrying on in the same direction and is at risk of cooking the motor. I thought you had to stop a single phase motor first before changing direction.

Am I incorrect?

My lathe and mill have 3ph motors, so its not really an issue for me, though I'd not want to attempt changing directions on the fly unless I was using collets, as I would be afraid of having a chuck landing on my foot.

Robin

 

[n4zou]

You never switch from forward to reverse while the motor powered!

When approaching the point where you would spin the cross slide handle to withdraw the tool from the work and disengage the half nuts you hit the motor stop button instead of the half nut lever. The motor and chuck will coast to a stop. You need to test this before you start threading so you know what to expect and the distance the tool will move during that coast down. When the chuck has stopped you reverse the motor via the forward/reverse switch and hit the on button. When your back at the starting position you again hit the stop button, wait for the chuck to stop, put the forward/reverse switch back in forward, move the cross slide handle back to zero, turn the compound handle moving the tool in to cut another pass, and then hit the on button again.

 

[miner49r]

It's done. A $6 DPDT on/on toggle did the trick.

Robin,
You are mostly correct. This single phase 1/2Hp motor with capacitor start can be reversed while running if the speed is brought down low enough for the centrifugal starting mechanism to activate. At this point the motor is nearly stopped anyway. Even so, this lathe has a spin-on chuck and I would never consider reversing it at speed.
I am just trying to avoid hand cranking the carriage back.

N4zou,
That is exactly what I intend on doing to cut this metric thread since the threading dial can not be used. I'll play with it tomorrow.

Regards, Alan

 

[Blogwitch]

Alan,

I would suggest you have a look at this current post and let it take you to wherever.

http://www.homemodelenginemachinist.com/index.php?topic=17234.0

The swing up tool holder is the cureall for a lot of people new to threading and old timers like myself.

Threading, both left and right hand becomes a pleasure to do rather than a pain. It lets you do it twice as fast and makes it semi automatic, you put the next cut feed on as it is retracting back to the start.


John

 

[miner49r]

John,
I have read bits about the retractable tool posts and thought to myself, "I can cut threads. Can it really be done easier?" You have proved it to me with your swing-up tool post. It is well thought out, easy to make, and simple to use.
I do have one small question. Your video shows the cutter dropping down when it is retracted past the starting point but does not seat completely on the key until the next cut is started. I would guess that it's not a big deal. Has this caused you any grief?
It's been said that mimicry is the best form of flattery. I happen to be tooling up to make an ER32 collet chuck to thread on the spindle. And then be able to move it to the rotary table. And then... and then... Sound familiar?

Best Regards, Alan

 

[Blogwitch]

Alan,

That hesitation to drop happens sometimes, but not always. I put it down to maybe temperature, tight gaps closing a little. When I actually stop the machine and gently touch the tip, it falls under it's own weight.

I spent a couple of years getting my tooling to be interchangeable between lathe and mill, and made a few slight mistakes in the very beginning, but now everything just fits into or onto each other with good accuracy, and is a joy to use. A few people have followed my lead and they have said that it saves them hours on setting up between machines, I found that out with the first pieces I made using the system.

Mimicry is fine, if the methods are OK with yourself to follow, but sometimes, peoples oddball machinery can't allow it to be done.

Just enjoy what you are doing.


John

 

[miner49r]

John,
I don't want you to think that I was criticizing in any way, shape, or form. I figured it was a tight tolerance and was curious. I respect your work and thank you for the tips you have graciously shared with us.
Alan

 

[Blogwitch]

Alan,

Of course, I realise it was not criticism, if you or anyone has a question about anything I have done, people only have to ask and I will do my best to answer. But you must remember, my memory is nowhere near as good as it used to be.

As things are now progressing in my private life, I should be able (with a bit of luck), in the near future, be showing new techniques that almost anyone can follow and do, rather than, at this time, relying on pointing people to what I have done previously.


John