rail cutting

[lgalla]

How would THK type rail be cut and machined for butt joints.Should a pin be used?I am not thinking of doing it myself,but would like to know how it is done and be educated in the process when approaching a machine shop.
Thanks
Larry

[electronicwood]

I joined three sections on THK-type rail for my router. I needed a pair of rails 7.5' long each and did not have the budget for one-piece rails. I set three sections of rail in a groove machined into a 7.5' long piece on aluminum and bolted them in place. I made the groove in the aluminum by placing two locators on the mill bed and sliding the aluminum along these locators for each cut. I took a little effort to get the locators parallel to the direction of mill travel, but it worked pretty well.

When I first bolted the three sections of rail in place, the bearing truck would not travel across the joint. I then had to unbolt the rails and lap the bottom of the groove in the aluminum until the bearing travel was smooth. This took several iterations of assemble-test-disassemble-lap-repeat, but I was able to get it done in one evening.

I'm not going to claim this is the best way to get a long bearing, but it does work.