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Another PM935 base

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kb58

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After reading about the lowish table height of the PM935, I decided to make a wheeled stand. Material is 0.187"-thk 2" square steel tubing with solid 6" wheels. The height comes from measuring the spindle height on my Grizzly 12 x 36 lathe (~47") and taking a guess about how high the mill stand needed to be to match it at normal working height. Never mind the distraction in the back :), that's for another thread.

After struggling for well over an hour trying to get the mill onto the stand, it was finally done, where hopefully it'll live out the rest of its life. (Only later did it hit me that we did it completely wrong: we should have just lifted the mill up off its pallet, then positioned the stand on a raised platform above the legs of the engine hoist. I'll spare you the embarrassing details of moving a 1500-lb beast laterally onto a stand...)

Since I ordered the 3-phase motor, I started cutting and drilling holes in the formerly brand new mill. It seemed reasonable that the shutoff switch and VFD could be located on the back of the column (in my installation) where they'd be protected from flying chips. In addition, all the 120-volt powered accessories (DRO, tach, up to three power feeds, lights) seemed to want four double outlets added to the lower access cover plate (I don't plan to run coolant). Still to do is final wiring and configuring the VFD.

Oh, and the paint (at least on my mill) is very brittle and susceptible to chipping. Please post if you've found a matching paint color.

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Fitter Bill

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Nice stand. I really like the car too.
 

Firstgear

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Great idea on the outlets on the back!
 

petertha

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Can you elaborate on your jacking rods. I assume you roll the machine & then level to floor? Looks like only 3 of them. Or am I misunderstanding purpose.
 

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kb58

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You're correct, there are only three. My reasoning is that with four jacking screws, the load cannot be equally shared. Once the mill base is bolted to the stand, the assembly is so rigid that it's impossible to tell (other than wrench torque) if all four pads evenly share the weight, or if one pad might even have zero weight on it. With three pads in a triangular arrangement, it's guaranteed that the load is shared evenly. It also guarantees that the mill base isn't undergoing any twisting torque. Lastly, since the pads and wheels are outboard of the mill base, it ensure it's less "tippy" than without it.
 
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petertha

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Thanks for your explanation. I get your logic. I have (4) rubberized machinery feet which compress a bit & there will be some minor amount of flex in outboard legs of the frame. Once the mill was leveled in 2 axis by successively jacking the screws, I thought I could feel a bit of differential torque between one foot which is probably exactly what you were talking about - indicating somewhat different load distribution. But within a quarter turn it gets smooshed up to feel pretty equal. And who knows may this change over time. The 3 point never even occurred to me. I think its technically more correct but depending on the geometry maybe offers a bit less enclosed support footprint, so choose yer poison LOL.

I have seen some folks plop the mill down on the floor or plywood which basically means the support footprint is the perimeter of the casting base (ie quite small). So I think any of our frame methods are an improvement & most agree it has to be elevated for the average height person anyways.
 

kb58

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If you guys use the Hitachi WJ200 VFD, I highly recommend using only the full (420 page!) manual. It contains far better explanations, and walks through getting the thing up and running the first time. Even has an introduction on adjusting parameters through the front panel, which the "quick start" manual pretty much leaves out entirely. It's pretty crazy how you can set it to run at a fraction of a Hertz, but it does.

Next up is wiring the variable speed pot and the remote reverse/stop/forward switch.
 
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