just finished up a new Vinyl cutter, and so far it's working great. Total cost was about 25 bucks, and it seems to do what the ~100 dollar ones do.
I wanted one that would chuck in my 1/4" collet, so I started with a piece of 1/4" brass tube from the hobby store. Then I cut apart a Roland blade holder that I already had and extracted the two bearings (one with an attached magnet) and the spring.
Next, I cut two bushings out of ABS to fit the OD of the two bearings and the ID of the tube. Of course, all four dimensions were different and required a number of trys to get right. The one for the magnet bearing needs to allow the bearing to move up/down in the tube, but the one for the plain bearing needs to be tight to the inside of the tube.
Then i cut the cutting end cover and an insert for the other end of the tube for a screw to screw into. This allows the depth of the blade to be adjusted easily. I sanded down the sides of the screw head so it would fit into the 1/4" collet (it was a little too bit).
Press-fit the bearing at the cutting end of the thing, inserted the spring in the other end, inserted the magnet bearing, then added a little super glue to the screw holder and quickly popped that in.
Gave it a try, and with a bit of trial and error on the amount of blade extending past the cutting cap, it works pretty well. I think it will work better once I machine a really level bed to cut on. My current bed is pretty level, but has about a .2 mm drop from one side to the other. Since the cutter is only sticking out a tiny bit (cutting the vinyl but not the backing paper), this makes enough of a different to make the cut fail.