Re-wiring a Dunlap 1/3 HP Thermotron Model #115.5454 Split-Phase Electric Motor

[btvarner]

Ok, here goes. My first post. Like most 1st postings, I screwed up & need help!

Background:
I have a 1941 Craftsman 101.03622 drill press. It is powered by a Dunlap 1/3 HP Thermotron Model #115.5454 Split-Phase Electric Motor. My dad bought the press in the 1940’s. I used it throughout my youth & when he died, I got it. Other than oiling it, have not done any other maintenance. The motor is split-phase. Has a centrifugal switch & a thermal reset switch. Also had an On/Off switch in the motor base. At some point, dad had apparently changed the wiring in the drill press. He installed an On/Off switch on the press itself in order to more easily turn the drill press on and off, rather than reaching all the way back on the motor. The new wiring layout removed both the thermal reset & motor base On/Off switch from the circuit. The new press mounted remote switch was also introduced into the circuit directly into the wiring panel through the opening. The 2 prong power cord was also run directly into the panel through this same opening. Other wires were just capped off in the motor base and wiring panel area. Needless to say it is a cluster.

The other day I “touched” the power cord near the motor and sparks flew! The power cord had been rubbing against the side of the panel entrance for years and years. Had finally worn through, and disconnected. As one side of the power cord had frayed through, the motor would no longer work. I removed the motor and re-tested functionality, once I fixed the cord. Works fine. It is such a mess however, that I thought it was time to go through the motor. I have very little experience in rebuilding electrical motors.

Issue:
Between the wiring being screwy and a lapse of judgement, I took the motor apart without FULLY understanding how/where some of the stator wires attached. One of the attached images is how I believe the motor was wired before I disassembled. I am not desirous of putting the motor wiring back together the way it was. I want to wire it as it came from the factory. But because of all the changes that had been made to the circuit before I started, I am having difficulty determining how to rewire correctly for re-assembly.

The Thermal Reset switch & Centrifugal switch seem to be in good shape. I bought a new simple On/Off switch for the motor base. I want to rewire all these back as they should be. I seem to be unable to find any wiring diagrams for this motor online.

Especially confused determining which stator windings are for start-up, and which is for running? There are several threads around on this general subject, but none seem to answer the wiring questions for this motor. Hoping I can receive some direction.

I did put the multimeter on the stator. One of the below images show the results of that test. Thanks in advance!

[spro]

Generally the start winding has noticeable less resistance than the run winding. It gives a "kick" to get things rolling and cuts out. Measure as close to the winding as you can, bypassing the thermal cut out and centrifugal switch.

[btvarner]

Thanks! Yes, I did take the measurements right at the stator, from the disassembled motor. Does this diagram look correct as a general rule for this type of motor?

[spro]

It does. The start winding can burn out if both fields are active under a load. The start/ cutout switch needs to be clean and well positioned in the motor body. The centrifugal weights, springs and thrust washers must be free to do their job. The thermal cut out/ reset saves lots of these motors.
I have a fairly old Craftsman DP in the basement but it has an induction motor. I placed a FWD/ REV switch at the back bell and extended a power switch to the left side of the head. It works fine for me because these DPs don't have a large "start up" current requirement. It runs and only has a 1/2" chuck capacity but may get to hogging. No problem. Back out, coolant or regrind/ replace the bit.. the motor can slow down without a start field being energized.

[btvarner]

Thanks spro, I have cleaned the centrifugal switch & it seems to function properly.

Ok, I still have an unanswered question. I do not know where the odd wire out of the stator goes? Wires 3 & 4 are the auxiliary winding. Wires 2 & 5 are the main winding. If you look at the second image I posted, you see the left most stator wire (It has a termination nut on it). I do not understand where to connect that wire. Everything else makes sense. If I cannot come up with an answer, I guess I will leave it unused/terminated. Would just like to know how that piece should go……. Thanks!

[Russ Hanscom]

Could it be a mid coil/winding tap, not needed for some applications?

[btvarner]

Something like that would make sense because this wire was capped and unused when I took the motor apart, and it had been running fine. I thought that winding taps only occurred on transformers?

[spro]

I was a little off with approximations about your motor. Your diagrams may not be correct if relying on my failing memory.. I replaced the smashed drum switch of a vertical milling head and drew some diagrams of how it was connected. T1 on mine is connected to T2 . T3 is connected to T4 but this all goes to the drum switch and its main use is to reverse the motor. Many leads are flipped and feed power differently. Your T1 appears to be T6 because it ties to the centrifugal switch, then thermal cut-out Then a capacitor. Well, its either T5 or T6 but it was an option, like Russ H said. You rarely need reverse with a DP unless using LH drills.

[btvarner]

Ok, starting to put this back together. I have studied & believe that the 1st stator wire is a winding tap. It was unused & capped when I tore the motor down. I am going to leave it that way going back together. Question. I have the ground (new 3 prong power cord) connected to one of the bolts that holds the stator onto the motor base (See image). Any reason why that would not work? Thanks!

[spro]

Looks normal to me. Case ground is really important with the polarized plug. Neutral white is pulling current the same as the black wires when the unit is working, so it isn't neutral then. The chaffed wire against the frame should blow a fuse or trip a breaker but GFI trips first.

[spro]

I see that your power cord retainer isn't up to specs - Oh dear, Yet I understand because I've done that too. I dealt with older things and they had like a "hog ring" retainer. It was steel ring and which wire was going to chaff into that ring ? It was against the frame or very close and built up metal particles around it.
From that Sears product # you can find which manufacturer built your Drill Press. I can't find my page but our friend Steve M would know.

[btvarner]

Thanks spro! I have the manual for it. Does not cover the motor however. The drill press plate: