Atlas Mill electrical woes

[canuck750]

This is a lengthy post, sorry for all the detail but my understanding of electrical is very limited and I am trying to diagnose a problem with the machine. Advice and explanations are very much appreciated!!

I recently purchased a very nice Atlas Horizontal milling machine model MFB.

The mill is equipped with a 1/4 hp, single phase motor, 120volt. there is a switch with centre off, forward and reverse. A new chord has been fitted from the machine to the wall plug. When I flip the switch to forward or reverse there are sparks visible from inside the machine, sometimes the motor will start spinning in F or R and sometimes the electric panel breaker trips.





I removed the rear access panel to expose the pair of electromagnetic contactors, there are two of these modules and each has four brass fingers that act like automotive points. I washed everything down with electrical contactors cleaner, used Q tips to wipe everything.
When I plug in the machine and flip the switch back and forth between F and R there are sparks shooting out from the corresponding points contact and a smell of electrical burning.









I removed the four wires to the motor and then flipped the switch back and forth, no sparks from the contactor points. Hook the motor back up and the sparks fly again.

I visited a friend who has a pump and electric motor company. He gave me a new motor to try out, this new motor has a pair of capacitor on the top. He showed me how to wire it up, two white wires from the contactor bus strip to the two white ‘line’ lugs on the motor. The two red wires from the contactor bus strip are joined to the red and black wires inside the motor access opening.







I hooked up all the wires to the contactor bus strip and I get sparks again when I flip the switch to F or R. I had the motor running for about 5 minutes in F and R. The motor case was very hot to the touch and I didn’t even have the drive belt hooked up to the spindle!

Something is very wrong.
While the motor was running it would sometimes seem to switch speeds up and down.
I am wondering if the old magnetic contactors are at fault?
I have a pair of new contactors I had purchased for my single phase 220 volt lathe, can I swap out the old contactors for these new 230v ones?





And if so any ideas on how to wire up these new contactors from the 120 volt wall outlet to the motor?

My crude wire diagram of the existing contactors and switch.

 

[TonyK]

Okay, I cannot trouble shoot a connection wiring diagram as I have know way of understanding the circuit for this machine.

Here is what I will suggest. Disconnect the motor and turn on the motor circuit and observe which relays pick up and if the contacts close. I suspect that the sparks are for the main contacts running the motor that are sparking. See if both contactors pick up then change to reverse and see if the other contactor picks up. I suspect what is happening here is that forward reverse start winding is being pick up at the same time by the contactors. Does the motor always start in the same direction? or does it sometimes start in one direction shut off and start again without selecting reverse and it starts in the opposite direction? The start winding should drop out once the motor comes up to speed if it does not then the motor will heat. The start winding is a short duration winding only used to produce torque to start the motor turning and since you tried another motor the motor is not the problem, it is one of the contactors.

TonyK.

Grimsby Ontario Canada.

 

[gerritv]

There is not way in h... that I would have exposed relay contacts below the gearbox and other oil spewing components in an Atlas Mill.

None of that stuff is original or IMHO desired. Get rid of all the wiring, replace it with a very simple line in to the switch and then to the motor. If the motor runs in reverse, change the wiring in the motor according to the plate.
Live happily ever after.

Not sorry to be blunt

 

[canuck750]

There is not way in h... that I would have exposed relay contacts below the gearbox and other oil spewing components in an Atlas Mill.

None of that stuff is original or IMHO desired. Get rid of all the wiring, replace it with a very simple line in to the switch and then to the motor. If the motor runs in reverse, change the wiring in the motor according to the plate.
Live happily ever after.

Not sorry to be blunt

A couple responses, the motor has a forward reverse switch, no idea if I need a reverse for this machine or if F and R were original to these.
The motor will start in the direction the switch is flipped to.
I agree that it is very strange to locate these big contactors exposed to the oil spewing off the gears!
If I just run power to a simple on/off switch and get rid of the contactors I assume I will have the machine Rubio g in only one direction which is ok with me.
The way the new motor is wired for F and R to the contactors, how do I wire it to run in just one direction?

 

[TonyK]

There is not way in h... that I would have exposed relay contacts below the gearbox and other oil spewing components in an Atlas Mill.

None of that stuff is original or IMHO desired. Get rid of all the wiring, replace it with a very simple line in to the switch and then to the motor. If the motor runs in reverse, change the wiring in the motor according to the plate.
Live happily ever after.

Not sorry to be blunt

You bring forth a simple solution.

As for how to wire the motor, we need to see the wiring diagram located normally on the motor wire terminal cover.

TonyK.

Grimsby Ontario Canada.

 

[gerritv]

2 pole single throw switch (single pole if you want to make it original). Power cord black and white to one set of contacts, 2 wires (preferably also black and white to match) from other contacts to Line In connections on motor. If using single pole, switch the black wire only. Green to frame ground, ensure motor is also grounded to same frame. If motor runs in reverse, then switch black and red per the motor plate.

I don't see a need to run the machine in reverse unless you have cutters that need to run in reverse. The issue then will be that the drive dog on the spindle will unthread under load if the taper slips.

 

[canuck750]

I just downloaded the Atlas parts manual and operation manual from Keith Ruckers web site. The contactors are definitely not stock, the parts page shows a simple on/off switch. I will pick up a new one/off switch, get rid of the contactors and just wire direct through the switch to the motor.
This is the diagram on the case if the new motor.



This is what is under the new motor access cover



There are two terminals with a 9mm nut that I attached the two white wires from the contactor bus bar. The two red wires from the contactor were joined to the black and red wires under the access cover, the red and black had flag connectors attached to blade lugs, my electric friend told me to unplug the red and black wires from the motor, clip off the flag connections and join one red wire from the bus bar to the black wire and one red wire from the bus to the red wire on the motor.
Now if I just have two wires and a ground from the wall plug and run one wire through a switch, to which terminals on the motor do I connect the black and white cord wires to?

 

[TonyK]

Terminal 4 ( white) terminal 1 ( Black), switch the black wire. Ground to the green screw.

TonyK.

Grimsby Ontario Canada.

 

[canuck750]

Thank you Tony!!

Very much appreciated, I picked up a single pole switch this morning and some black and white wire to do the job properly, out with all the old electronics.

 

[canuck750]

Discarded the pair of contactors installed a single pole switch h and it works like a charm, the motor is quiet, no hesitation starting up and the motor remains cool



The inside of the machine is now empty except for the wires to the switch and motor, encased in plastic sheathing I use on my motorcycle restorations and a molex quick disconnect to isolate the wall cord from the rest of the wiring.



Thanks again for the advice and instructions on how to wire the motor.

 

[jorogi]

Well dang, one less project, whatever will you do ?

 

[gerritv]

simple is best for reliability

 

[mickeyf]

There is not way in h... that I would have exposed relay contacts below the gearbox and other oil spewing components in an Atlas Mill.

As usual, I missed this post when it started.

I had this same model of mill some years back. Yes, there was quite the puddle of oil inside where those contactors would have been. Mine had just a simple switch, which appeared to be original. The only reason for more than a simple switch for a motor that size would be to prevent the motor from restarting on its own after a power failure. But even that would not require as complex an arrangement as was shown at the beginning of of this thread.

 

[canuck750]

I ran the Atlas horizontal mill today making my first cut on a small scrap of aluminum. Without paying any attention to speed or feed I just put the block of alloy in the vice and ran the power feed taking about a 1/16” deep cut. I am
Impressed with this small machine, pretty decent finish for just a test cut.


I love these old machines, it’s a nice match to my Atlas 7B Shaper.



Now to weld up a rolling stand for the mill.

 

[whydontu]

A suggestion. Recently become a big fan of E-STOP switches. Put one in series with your on/off switch. Hit the big red button, everything stops. Princess Auto, $14. My preference is a rotary on/off and an e-stop. Means no accidental starts if your shop smock sleeve gets caught.

 

[canuck750]

A suggestion. Recently become a big fan of E-STOP switches. Put one in series with your on/off switch. Hit the big red button, everything stops. Princess Auto, $14. My preference is a rotary on/off and an e-stop. Means no accidental starts if your shop smock sleeve gets caught.

View attachment 63427

View attachment 63428

I like that idea, I didn’t know Princess Auto carried these, even though I am probably in there once a week. I should have these on all of my machines, another project to get on with.