[bobmagnuson]

When looking at Hiwin rails and blocks, the rails are available in various accuracy classes and the blocks are available with various levels of pre-load.

What should we be looking for when selecting rails and blocks?

[ger21]

Normal or High precision, and Light Preload. I would think that the higher precision levels get much more expensive.

Assuming this is for a router.

[wizard]

For a router you have to consider the potential accuracy of the machine but in most cases i dont see a reason to go to the higher accuracy rails. The thing is this, unless you can machine the frame to a high level of accuracy you are simply wasting money on high accuracy linear scales. That means flat mounting surfaces, accurate locating shoulders and planes accurately square to other axises. In other words if you are using T-slotted aluminum or plain steel tubing you don't have the accuracy to justify high precision rails.

As for a preload id probably go mid way but again design is an issue here.

In a nut shell the vast majority of home built machines can't do anything useful with high precision rails. That will change to some extent if you are building a much stiffer machine than is the norm and have the machining resources to properly setup the mounting surfaces. While i don't like to use the phrase all the time "it depends", but in a nut shell you waste money buying to much precision for the frame in question.

[bobmagnuson]

Thanks for the information gentlemen!