HiWin rails

Hi All,

Just fixing up my router at home and need to buy new rails and need some quick advice. My x axis has a 500mm travel. I mostly cut wood, plastic and some aluminum (small shallow cuts only). It holds about 2kg of spindle.

I already have 1 20mm rail and block and to buy another would cost me the same as getting two 15mm rail and block set. I would then have a spare 20mm rail too :).

What do you think would be the better rail to use for the x axis out of 15mm or 20mm hiwin rails? Do you think the 15mm should be OK?

Thanks