# PM-45-PDF powered head lift conversion



## mskobier (Jul 4, 2013)

All,
    I stated in a different thread that I was in the process of adding a powered head lift motor to my PM-45-PDF. I thought it would be better to not hijack the other thread so I started a new one. Here is a link to the original post, and pictures of where I am currently at in the conversion.

http://www.hobby-machinist.com/show...ving-the-head-height-crank-to-the-front/page2

Due to it being over 100 degrees in my area, and that my garage was way too hot to spend as much time as I would have liked working on the project, I did not get the mounting brackets finished last weekend. The temp finally broke, and I was able to get the brackets finished. So here are some pictures of where I am at in the conversion.

All that's left for the mechanical mods is to cut the keyway in the Z axis lead screw, bore out the lovejoy coupling for the lead screw, mount the lovejoy on the lead screw, reinstall the lead screw. Position the motor, and drill the mounting holes on the top of the column.

Yes, the counter sink hole in one of the corners of the mounting plate is a mistake. It was very late and I was tired. Fortunately, I caught it before I finished sinking it. I thought about making a new plate, but decided since it would be facing the column, not visible, and did not affect the strength of the mount to any great extent, I decided against making a new plate.

Next comes the electrical mods. This is probably the most difficult part of the conversion. There are two ways to do the wiring. Since the lift motor is a 120v AC motor, I need to be able to provide 120v to the motor. The mill comes wired 240v AC three wire. That means two hot legs and a ground. I either have to provide a separate 120v AC power cord for the lift motor, or modify the mills wiring to use 240v AC 4 wire. Which is two hot legs, a common, and a ground. Since I do not want to mess with the factory wiring, I will be installing a 8"x6"x4" NEMAa box on the rear of the mill where I will bring in the 240v AC four wire, then break out the two hot legs and a ground to power the mills factory electrics. Then I will tap off 120v AC from the 4 wire to power the lift head. I will also be installing a couple of receptacles in the sides of the NEMA box to provide power to the powered cross feed. I got that idea from another post on this forum.(thanks sanddan!) 

I figured out that I can reverse the motor by using a 4PDT center off toggle switch. The switch I purchased is a center off, spring loaded on on. The spring returns the switch to the off position when I release it. I will need to provide 6 wires to the switch. Two of the wires provide the power, the remaining four take care of providing power to the motor and reversing motor direction. I had to order a new NEMA box since I did not have one of suitable size for this project. Hopefully early next week the box will be in and I can install the electrical.

Well, this has been quite a long post. Hope you enjoy the pictures.

Mitch


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## mskobier (Jul 19, 2013)

All,
   Sorry I have not posted much on the powered head lift mod. I had to replace the roof on my home and garage over the past couple of weeks. I sure am glad that job is finished. Nothing like stripping shingles during 100 degree days!

As for the head lift mod, I have changed some of the design criteria. I have decided I want to add limit switches to the electrical circuit. That way I do not have to worry about running out of lead screw and stalling the drive motor. It probably would not hurt anything, but I do not like the possibility of over stressing parts. So with that said, I had to add a pair of contactors to the electrical box on the rear of the mill. The contactors are 24VAC operated, and I will be tapping off the installed work light transformer to supply the power. That way there is only one additional wire running from the control head to the control box. I already have a few sealed industrial limit switch assemblies I picked up at the salvage yard some years ago that will work perfectly! I was able to find a pair of mini contactors on fleabay for not too much money that have plenty of current capability and the 4 necessary NO contacts (poles). They arrived yesterday. Hopefully I can get a bit done on the machine this weekend. I'll post a schematic drawing of the electrical circuit when I get shortly. 

Later
Mitch


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## mskobier (Aug 4, 2013)

All,
   I actually got a chance to spend some time on the power head conversion today. It won't be long now. I made up a temporary support for the mill head so I could remove the lead screw and cut the keyway. Getting the lead screw out was quite easy. Hopefully it will go back together just as easy. I verified the dimension of the end of the lead screw. It is .780", or 19.8mm. Seems like an odd dimension to my, but who am I to say? Anyway I'll bore out a.750" ID AL-075 lovejoy coupling to .780" to fit the shaft. This made it necessary to cut the keyway in the shaft about .015" deeper than normal. So instead of .09375", I took it to .109. A little deeper than necessary. I am still learning just how accurate the quill dro is. I took about .010" cuts, and used a fairly slow feed with the power cross feed. Anyway, here are a few pictures of what I have been up to.


Mitch

This is the first keyway cut I have ever made on a mill! I've made many things on the old 9x20 lathe, but the milling machine is a whole new ballgame. This milling stuff could get addictive!!!


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## ChipsAlloy! (Aug 7, 2013)

Nice, keep up the good work! 
I am thinking of making a frame similar to what you did for the cast iron base *for* my pm932.


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## Ray C (Aug 7, 2013)

When do you get your mill?




ChipsAlloy! said:


> Nice, keep up the good work!
> I am thinking of making a frame similar to what you did for the cast iron base of my pm932.


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## ChipsAlloy! (Aug 7, 2013)

Soon I hope!

Ray Sent you an PM , I dont want to polute mskobier's thread!


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## mskobier (Aug 9, 2013)

All,
  Just to give an update on the power head lift I have been building, I got the motor installed the other evening and was pleasantly surprised that I could still use the hand crank without much additional force being needed to turn the crank. I also temporarily wired the motor to see how well it was going to work. The hand crank turns about the same speed as if I were turning it by hand and the motor had no problems lifting the head. I checked the amperage necessary to lift the head, and it measured at 1.35 amps. The manufacturers specified max load current for the motor is 1.6 amps. Well within the comfort range of the motor. I tried both up and down, and really did not notice much motor noise difference. It just makes a light hum going up or down. It did coast just a tad when coming to a stop when going down. That was to be expected. At this point I am very happy with my choice of motor. I plan on making a new hand crank shaft that is a little longer so I can make a cogged type of assembly like on the table hand wheels, so I can attach the hand crank when I need to make precise head height adjustments. The hand crank will stay on the tool cart until needed. Now just to finish installing the electrical controls.

I do have to make a minor modification to the lift head motor mount. The rear two mounting holes are too close to the rear edge of the column. The rear holes are only about 1/4" from the rear edge. I could drill and tap the holes there, but I want it to be a bit farther in. I plan on moving the mounting holes about 1/2" farther in. That will give me plenty of material to drill and tap. 

Mitch


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