my first build

[irving2008]

...being a noob i am not sure what a pillow block is. do you mean a small square of mdf with a hole for the bearing? you then make a hole larger than needed in the machine chassis so that the pillow block can be moved to line it up perfectly?

A pillow block is just a bearing mounted in a carrier, usuall cast or pressesd steel with ears to bolt down with. you can buy them ready-made or, for this purpose, two 12mm id races mounted at equal height in some blocks of MDF screwed to an MDF base will suffice... its only to provide some support for the leadscrew while its being worked on so moderate accuracy only needed...

also, if i am going to get some thrust bearings i need to understand them a little. my understanding of thrust bearings is that they handle the load laterally along the length of the screw but they have no ability to handle side to side loads. do i need a ball bearing and a thrust bearing in each pillow block or am i missing something?

For the actual machine you need a bearing block which retains the leadscrew radially (ball race) and axially (2 x thrust bearing), alternately you'd use 2 x angular contact bearings but these are hard to find in small sizes. See the pic for a guideline