Bearing questions and Rails questions

Mostly Printed CNC - MPCNC Advice
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So I am going through the parts trying to build out a good quality mpcnc.

 

First bearings

How important are the bearings? I was discussing the build with my brother in law who offered me skf bearings 608-2rh for an incredibly good price. It will of course be more expensive than cheap Chinese bearings but he is offering me enough to finish the build. So if I were to buy them would I see better prints over cheap Chinese?

 

Next the rails. I’ve read stainless steel is more Ridgid. I plane on doing a 2ft by 2ft build and I want to do aluminum milling. Is stainless steel going to make a drastic difference in the quality of the mill?

Sorry for the questions.. I am experienced in 3d printing but new to milling/cnc

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If you buy the cheapest bearings you can find, they may well not be very smooth. I did, and I was unhappy with how they felt. I don’t know if it would have mattered in the finished machine but I bought better bearings anyway so I wouldn’t have to find out. Probably chinese not-quite-cheapest is fine, but if you have a line on quality bearings for decent price, I would go with that and save time.

At 2’ x 2’ the rails wont matter much. Conduit should be fine. At those dimensions the Z height is the most critical thing.

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Thanks for the response. I'll talk with him and get them then. Also guess I'll do emt first and if I don't like the result then I'll do stainless

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If you do switch to SS from EMT, you may need to print up a batch of new parts… something to keep in mind.

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You will need to print all the parts if you change up to 1 inch stainless.

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Hmm that’s a lot of work so guess I better settle on what I’m doing.