Linear shaft end-for-end alignment

[krumly]

I have several 46" long pieces of 1/2" pre-drilled linear shaft, hardened. Shaft ends are eased/deburred. I also have aluminum suport rail. I want to use them end for end to extend my x-axis length. I have not purchased the linear bearings yet. What sort of luck will I have aligning them end for end with the bearing running acros the joints?

Do I need to have the ends re-machined and dowel pins added for alignment? If so, can that be done with the shaft in the hardened state?


I looked through the theads on linear rail alignment and understand the need for an accurate reference line or edge for alignement, but didn't find explicit answers to the end-joining question. Thanks,

krumly

[Jason Ross]

You need to grind the ends of the rails until they are perpendicular to the center line of the shaft before butt joining.

Lee Controls makes a roller bearing pillow block that probably could jump over the lead in edges. It also can tolerate some misalignment.

[Smackre]

The linear Rails are only case hardened so Drilling holes for pins in the end shouldnt be a problem. And i would think if you would grind the ends flat it would work alot better than having chamfers on the ends.

[krumly]

Thanks for both your answers.

I called Nook Industries yesterday, and the sales rep said they have butt joined rails even without the dowel pins successfully using roller bearings in pillow blocks. The dowel pins would have to help. Smackre is right -the rail ends could be drilled. I think I'll have someone with a lathe and steady rest bore the ends on pair of section for dowel pins, face then clean, and test a with an open linear ball bearing pillow block.

krumly