Hi. I'm a newbie here and have just started the well trodden path of cnc router design. There are some great designs and engineering skills on show on this site.So here's my first (of many) question. I have come across lots of designs using skate bearings running on round rails for the linear motions.These bearings are currently just over £1 each on ebay and typically 6 are needed per bearing unit. I have found a supplier of open linear bearings (20mm) for about £6.50 each. So given that there is not much price difference and that linear bearings only require a few accurate holes to be drilled in a block of aluminium to mount them, why use skate bearings? The complexity of the mounting arrangement alone would seem to be a good argument against.Can anyone throw any light on this?

Thanks Paul