So I'm new to cnc and have got a kit machine.

The spindle it comes with is a hi torque spindle, however it only has a 1/8" (~3mm) shank.

I'm thinking of getting a router on amazon and dissecting it and mounting it on the machine to give me up to 1/2" collet size. I'd only really need 1/4" (~6mm) as most decent milling bits come in that size.

my issue at the minute is not making the mounts (I can machine them with the curet spindle) but ensuring the new spindle is straight in the mounts so it cuts straight down and leaves straight edges on pockets etc.

Any tips on how to do this?

And actually how to get the profile of the new spindle for the mount (cut from wood by hand first maybe?)