Best orientation for linear bearings?

[kerino]

I'm still in the design stage for my router table, and was wondering about the best place to mount the linear bearings for X and Y axis.
My natural inclination is to mount them on the top of the side rails, but this leaves them exposed to all the dust.
Mounting them on the sides affords them a bit more protection, whilst mounting them 'upside down' underneath the side rails gives them maximum protection.
What I don't know is the pro's and con's of the different methods, and if mechanically there is an optimum orientation.
I am planning to use rectangular section linear bearings.
Any comments would be most welcome.
Kerin

[widgitmaster]

For the x-axis:
Mounting them underneath where it is clean would be my 1st choice!
Mounting them as far apart as possible is also important for stability.

For the y-axis
There are several designs for placement of the linear rails, all work well! But if you want to include a rubber bellows to cover the exposed rails and lead screw, then you have to design around the requirement of the bellows!

Eric

[Rhodan]

I saw a milling machine yesterday that used coiled plastic as a shield for the leadscrew and nut. Basically it was just a long strip of plastic rolled up and connected to the frame at one end and the axis table on the other. Seemed quite simple and effective.

[kerino]

Thanks everyone for the info.
Any ideas as to who makes the plastic coil covers?
Kerin

[ger21]

Some types of linear bearings are designed to carry larger loads when mounted on their sides, some when mounted normally. But your probably no where near the load limits, so it shouldn't really matter.