round vs square guides

[3Dsigns]

Between round and square rails; which is the most accurate and durable?


Also, those supported round rails with the open trucks. Do those tend to get loose with time?
Thanks

[Switcher]

Originally Posted by 3Dsigns Between round and square rails; which is the most accurate and durable? Also, those supported round rails with the open trucks. Do those tend to get loose with time? Thanks

1) Both rails should be the same, as far as accuracy & durability.

2) Supporting the round rail towards the middle of the rail is the biggest challenge (rail flex), on the square rails (THK, etc...) they can be adjusted with a simple shim. With round rails you could make a simple diy mounting block, bore a hole & just insert the bearings (sleeve).


Mounting block Round Rail:
http://www.vxb.com/Merchant2/graphic...1/kit659-1.jpg


Mounting block Square Rail:
http://torchmate.com/overview/slide4.jpg

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[3Dsigns]

Thanks Switcher!

[Switcher]

Also, I would never buy a THK style rail that doesn't already have the matching trucks with it (you might have a hard time finding a match later on).

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[walter]

"GK" is the symbol for blocks and rails ordered separately. You can find "GK" blocks on Ebay, add store bought "GK" rails and they will match perfectly.

[Zumba]

Round rails have a cheapness advantage. They send them through a centerless grinder the way you'd send wood through a planer. The blocks are also cheap to make. Extrude a big long piece and chop it into small blocks. Then shove in the bearings. The bearings alone are ridiculously cheap. A large supplier can get em for under a dollar a piece (20mm).

However, for a CNC, you wanted supported rails. Add in the cost of the T-shaped support, drilling, and tapping, and the cost savings are gone. You also get dismal load capacity and very tall profile (no good).

So in conclusion, there really is zero benefit to using round rails. If you're building a low accuracy hot wire foam cutter, different story. For a router, the square rails can't be beat.