All,
I joined this group a few months ago when I was looking for an RF-45 class mill. I settled on the PM-45. After the machine arrived, and I got it set up, I discovered that I hated the left side mounted head crank and decided to convert it over to power lift. It takes 130 turns for full travel of the head!
I did a a lot of internet research and remembered that the Grizzly G0755 mill comes with a powered head lift. I downloaded the owners manual and looked at the specifications of the lift head. It is rated at 1/8hp and is a gear head motor. It did not say what the rpm or torque rating was. I measured the handle of the crank, attached a cloth bag to the handle and started adding 1lb weights until the handle started to lift the head. It took about 10lbs to get it to move. I added another pound for good measure and multiplied the handle length (8") by the weight to get the in-lbs needed to move the handle. That works out to about 90 in-lbs.
I did a bit of ebay searching and found a gear head motor manufactured by Bodine that was rated at 1/6hp, 135in-lbs of torque, and turned at a rate of 57 rpm. A bit slower than I would have liked, but plenty of power to do the job. The motor also was 120V AC and was a four wire reversible. I located one of these motors in very good used shape for about $100.00. The output shaft is 3/4". The Z axis lead screw has the top end turned down to .780". A little more thinking and realized a lovejoy coupling (AL-075) with a 3/4" bore could easily be turned out to .780". So I purchased the necessary parts for the coupling. After a bit more measuring, I figured I needed to make the motor mount approx. 1.75" thick so there would be enough clearance for the motor and couplings with just a little bit of extra for clearances. Then figured out the wiring necessary to make the motor reversible with only using one toggle switch. The switch I am using is a mil spec, sealed toggle that is spring loaded center off and momentary contact for the two on positions. (momentary on- off- momentary on). It is a 4PDT center off switch. It also came from ebay. So with the motor, switch, misc wiring and hardware, I am into the power lift approx. $150.00. With a little bit of luck, I will have the lift motor installed this weekend. One large obstacle is that the z axis lead screw is not keyed. I will be building a support frame for the head and locking it in place. I will then remove the lead screw, mount it in the vice and cut a 1/8" key slot in the shaft. After fitting the lower lovejoy to the lead screw, I will reinstall the screw and mount the head. Again, hopefully this will all be completed this weekend.
I weighed the head on my mill. It comes in at 145lbs. I found a source of 120lb rated gas springs that if this all works out like I think it will, then I will purchase a set, install the springs, and replace the motor with one with a faster speed. The ones I am considering turns at 85 or 115 rpm with 90 or 68 in-lbs of torque. With the gas springs taking the gross majority of the head weight, it will not take much torque to move it.
Anyway, sorry for the long post. I figure you guys may be interested in how I am adding power lift to the head of my PM-45. I'll try and take some pictures during the mod this weekend.
Mitch
