linear rails

[ljoe1969]

does anyone know of a place to get inexpensive linear rails?

[Cold Fusion]

I've found that ebay is the best place for linear rails. I plan on using 1.25 round rods and thomson bearings/blocks. The whole setup it going to cost under $100 for both X and Y.

[samualt]

Ebay is the best place to get rails. But, you have to watch out for prices. I paid about $499 for a pair of new THK rails that were 8' long w/4 bearing-blocks. I saw the same thing go for $800 a week before and after. Sometimes you just have to wait for that perfect item and price.
Also, if your looking at THK rails, the shorter the rails the much smaller the price. I picked up some 14" THK rails w/6 bearing-blocks for around $20.
THK rails are affordable, but you just have to wait for a good deal (several weeks).

If you need really cheap go to thomson shafts and such.

[High Seas]

Ditto that - and another possibility - search the site here - you CAN join the rails. So several smaller pieces might add up to a bigger rail at a cost saving -- OPPS did I let out a secret
Better make sure they're the same size though and maybe ready to do some machining.
Jim

[xairflyer]

This is the holy grail of home made CNC !

I have been trying to source a slide I seen when visiting a company that manufacturer robotic type machines for production lines.

It was identical in appearance to a linear ball type slide, but the bearing surface was plastic, they run on round bar from 5/16" upwards.

All the machines I seen were using 5/8" and 3/4" sizes, the bearing unit fits into a block of aluminium like other types and is held in by circlips on each end.

The guy told me these machines run 24hrs a day and they last as long as ball bearing types, but at about 1/4 of the price.

[dlenox]

seen a lot of linear rails, both round and rectagular. many of them for sale on Ebay have only single bearing per rail.

is it adviseable to use 1 or 2 bearings per rail? my assumption is to use 2, but are there cases such as z-axis where single bearing will work ok?

[Cold Fusion]

It would depend on the load you put on it. For a smaller machine cutting light woods it should be ok. Another thing to think about it when you use twin bearing pillow blocks is that they take that many more inches off your available cutting area.

[pack rat]

I have assambled gantry on two 1" shafts using twin Thomsons bearings on each shaft. There was a sag in shaft of 0.020. I added the weight of 30lbs on top of gantry and sag went up to 0.040. The shaft was NOT hardened. Span between support was 43". Now I am going to supported rails.