Why NOT plastic for a base plate?

Make your own HDPE base plate - for free. Most plastics used for food containers is HDPE (Recycle triangle #2). Just put a container big enough for your plate in the oven with enough HDPE scraps to fill it up and melt it to a flat pancake. Once you have your "raw" material, machine it normally to your final specs.
 
Not to be snarky, but they call it plastic for a reason. ;) I think I'd go with steel. ymmv

Tom
 
KyleG said:
Not a snowball’s chance in heck I’d trust HDPE for that. I would definitely use steel.
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What is your concern about HDPE? Heat isn't really a problem, it never gets so hot at the base that it could melt the HDPE.
 
Plastic tends to deform or even flow under pressure or heat. So it may not be dimensionally stable enough for your application. If the material flows enough then the fasteners will not be tight any more. Usually that's a problem, especially with a motor. Personally, I'd use phenolic or steel. Depending on the size, steel may be less expensive than phenolic.

You can always try it. It might work and the cost is attractive. Report back with your results and a follow up in a month or two of hard use. If it's all good, we will have learned something.
 
Last year I replaced the single speed motor on my PM mill with a 3HP 3 phase motor. As you've discovered, mill motors have a unique face mount, usually integral to the end bell of the motor.. My 3 phase motor has a "foot" mount, so I had to cobble up an adapter. I used a 1/2" aluminum plate for the mill face and for the back and sides of the mount. It's worked well for over a year. If you can get it inexpensively, I'd certainly suggest you use aluminum, rather than UHMW. Phenolic would probably work, too, but it's not as strong as aluminum.
kHPIM0286.jpg

Millmotor Old and New RHS.jpg
 
Phenolic is easy to make. It is layers of fiberglass cloth placed in a mold that is squeezed to force out all of the excess resin. Use lots of fiberglass cloth. Way more than the thickness you want to end up with. You will be surprised at how much it compresses. Search on some of the knife making forums for more info. They use the process to make custom knife handles. Phenolic also used to be used to make blocks for sailboats.
 
I made some clamping plates for an AR receiver out of plastic cutting board material. I believe thats HDPE. They softened under cutting oil, (maybe wd-40?). Almost messed up the receiver as a result. So I’d be wary. Sorry, been a while, so details are vague!
 
What is your concern about HDPE?
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My biggest concern would be bearing stress under the fastener heads, especially under the fastener in the slot. I think the plastic will yield when you tighten down that clamping bolt. Honestly, I would even hesitate to use aluminum for that reason.

My secondary concern is that the motor will twist/bend the plate due to the moment from the belt tension.

Sorry if the first response was a little short, I was on a cell phone.
 
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