Deflection in precision rod rails

[irving2008]

Just by way of interest for prospective builders there is always discussion about what rod should I use... 12mm or bigger...

Well here is the measured deflection of both 12 and 16mm rod (500mm long in SK type mounts) under 5kg load.

In this experiment the mounts were not clamped up nor were they bolted down so the deflection of the rails themselves will, in reality, be less than this although the MDF base will deflects some as does the MDF 'table'.

2 x 12mm rod = 0.25mm (theory .08mm for rigidly fixed ends to .3mm for unfixed ends)

2 x 16mm rod = 0.1mm (theory .025mm to .1mm as above)

(i.e. if the clamps aren't tight and the supports not bolted down the rod flexes more)