Homebrew PCBs

Hi Charlie,

I would use skateboard bearings. They are available in ABEC7 accuracy 
for very little money. Skate bearings are standard 608 size metric 
bearings, 8mm bore 22mm OD 7mm thick.

Steel chain would almost undoubtedly be less accurate than a toothed 
belt.  Apart from wear issues and manufacturing inaccuracies, chain does 
not roll over sprockets smoothly. You get little jumps in the motion as 
each link folds around the sprocket.

Les


On 09/09/10 09:47, gandolfreefer wrote:
> Les, thanks, I see your point about flat ground stock.
>
> I do remember being amazed at how inexpensive flat ground stock really is when I used to order it for various milling tasks, especially compared to trying to make some oneself!!
>
> What would you recommend for bearings to run on the ground stock? Will regular plain old sealed ball bearings from McMaster-Carr do?
>
> yeah, unfortunately, the only ball-screw drives at McMaster-Carr are horribly expensive, seriously expensive, that's what got me retreating to toothed belts. I don't suppose....steel chain will work? It does wear over time and "stretch", but it seems to me this is a pretty light duty application for chain, and perhaps if the chain was a bit oversized for the app, it would wear very well?
>
> Best, Charlie
>