Profile Rail mounting. Top or Side?

[Falcon69]

So, another post got me wandering, and I'm thinking of redesigning my machine.

I'm using 30mm Profile rails and Bearings.

What is the way I should mount them? On the top or the side? Meaning, the top of the bearing block face upward, or to the side?

I think the top mount is better, but, it would be prone to alot more debris, while mounting on the side would only make the top of the profile rail collect debris.

So, I'd like your feedback and I've posted a Poll for this.

Falcon69

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[dmalicky]

There's no 1 answer, except that it doesn't really matter to the bearing -- profile bearings normally have the same rated load in any direction.

The rail mounting bolts are slightly happier if the rail is loaded in compression than tension. But a router is unlikely to stress a 30mm rail.

The overall configuration design does matter: rail spacing, moment arms to the cutter, distance between the 2 blocks on a rail, aspect ratio of 4 block pattern, and especially the ease of aligning 2 rails parallel to each other. So mount them however to best achieve those objectives and manufacturability of the machine.

[louieatienza]

If they're 4-way equal load type rails, you can mount them any way, as long as it's secure. Some rails/blocks are made for horizontal mounting only. Of course there are many commercial machines have them nounted both ways with no problems. There are a few guys here who have made a machine from DataCut plans, where the rails are upside-down under the table....

[Rooski]

I have mine mounted on the top of my table. My table is 114 inches long with a 66 inch gantry and I am using 25 series rails. All is working just fine without any imperfections in cut accuracy. It just seemed easier to design the table this way.
Also, if you have a good dust collection system there is generally little to no debris to worry about. I always check following each job and clean wherever necessary anyway though.