Prusa i3 rods

Hi,
I am about to order my rods from mcmaster carr. Do you guys have any advice on what type of rods I should get in terms of material? Thanks in advance.

The more you spend, the better you get.

Are you ordering thread rod or smooth rod or both? For the smooth rod, surface hardened / chrome plated / ground rod is a real good idea.

Generally you'll find small reprap specific sellers of things like rods are just buying them from their local hardware store. I've picked all mine up recently from a UK retailer called Wickes and they've been spot on - no bends or anything like that. It only starts really mattering when you get to M6 or lower it seems as the M8 and M10's seem to be ok from almost anywhere. I had a few bent M6's from an online retailer not long ago.

The issue isn't bending. The issues are 1) accuracy - how close to the indicated diameter they really are (and as a result how well the bearings ride on them) and, perhaps more critical, 2) hardness. Its amazing how fast rods that are not hardened can have channels gouged out of them by repeated passing of the bearings.

I bought cheap rods from McMaster, and I cringe every time I run my hands along particularly the x bars. For now they serve the purpose, but I plan on replacing them soon. Also, McMaster is not the issue. They are a fantastic vendor with a tremendous inventory. They have the rods you need, they just cost a bit more.

Ball bearings are *really* hard little gizmos. A linear bearing concentrates all it's force on a very small area of the ball bearings. If the rods are (a bit) soft you get grooves. You can get O1 (oil hardening) rod cheap. The issue is that you then need to oil harden it. It's soft when you buy it. Harding the stuff *and* keeping it straight - not so easy. Let somebody else deal with the hardening stuff ....

I never thought of it that way. I didn't realise that some of them would be softer - thanks for sharing that

I'd assume that if you can find an old inkjet printer with the correct size rods, they'd presumably be of decent quality and strength?

You never know what they did in an inkjet printer. They may have gone with bushings rather than ball bearings. That would make the wear issue a bit different.

The next layer to the puzzle is the bearings. Different rod has different diameter tolerances. The bearings come in a very limited range of choices. Best bet seems to be to get one rod and one bearing. See if they work together. If they are tight, that's not a good thing. Buying both the rod and bearings from the same guy is another alternative. I'd make it very clear that they need to work with each other before I sent him the money.....