How much motor torque to raise mill head?

D

daved20319b

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So not exactly a CNC question, but I'd like to add a power head lift to my Grizzly 0619 (Sieg SX 3) mini-mill. So far, it's all original, and I bought it brand new. It hasn't seen a lot of use, but I'm hoping to change that. Seems this is NOT an especially popular machine in the aftermarket, lots of options for machines with the head lift at the top of the column, but this one is complicated by having the handwheel at the front of the machine.

So specifically, does any one know how much torque it takes to raise the head, i.e. how big a motor do I need? And would I be better off with a DC gear motor or a stepper? Direct drive or re-use the existing gearing, I think it's a 2:1 reduction, or switch to cog belt? Also, what would be a reasonable speed? For short bursts, I can manage 5-6 IPM, but that slows down a lot if I have to raise the head very far. BTW, probably obvious but I don't use the handwheel for fine Z axis work, just to get the head as close to the work as possible so I'm extending the quill as little as possible. Another BTW, I've seen/read other ideas, bigger hand wheel or even a power drive at the handwheel, but I really want to dispense with the handwheel entirely, and get the lift mechanism on the column. Thanks!

Dave
 
Priest Tools has a kit for the LMS 5500/5550 which may give you some ideas:

 
Yeah, those kits are pretty easy to find, the later Grizzly, LMS, and PM mills all have the Z axis handwheel at the top of the column. The particular Grizzly I have has it on the front of the base, just to the right of the Y axis handwheel. IF I actually used that handwheel for Z axis adjustments, it would be a lot more convenient than on the column, but for my use, it's just in the way, AND it's a workout having to raise and lower the head. But thank you anyway. Later.
 
Best way is to measure the torque- use a spring fish scale or even a bathroom scale or a torque wrench. Attach a lever to the crank
so you can get foot-pounds. A torque wrench would give you a direct reading and is probably the easiest way to do it.
Then you would add something like 20% to that number and then you can go motor shopping and it'll work the first time
 
daved20319b said:
Yeah, those kits are pretty easy to find, the later Grizzly, LMS, and PM mills all have the Z axis handwheel at the top of the column. The particular Grizzly I have has it on the front of the base, just to the right of the Y axis handwheel. IF I actually used that handwheel for Z axis adjustments, it would be a lot more convenient than on the column, but for my use, it's just in the way, AND it's a workout having to raise and lower the head. But thank you anyway. Later.
Click to expand...
The 5500-5550 have the Z-Axis hand wheel on the right side of the head
 
Quite a few years ago I built a knee drive for my BP mill. I determined the required torque by making an adapter to use a torque wrench directly on the shaft for the manual hand wheel. I placed 200 lbs of lead on the table and then took the torque readings. It has worked out well.
Ted
 
Thanks for all the suggestions, guys. I tried my torque wrench, but it only goes down to 10 ft. lb. So then I pulled out my Wheeler Fat Wrench, it reads either in. lb. or Newton-meters. Turns out it takes less than 2 N.m., and that's at the acorn nut that holds the handwheel on. That handwheel has a 2:1 reduction ratio, I'm a little fuzzy on the physics, but I think that means that even if I directly drive the head lead screw, I should still need less than 4 N.m. of torque. Can someone critique my math? Thanks again!

Dave
 
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