Scanhead almost done

It has been a few days and I’ve made some progress.

Scanhead

The scan head is almost done! The only thing left now is making some sort of post to hold the tip and maybe some tension solution to keep the whole thing rigid.

Top half

I found a drill bit of suitable diameter for my fine adjustment screw. It does leave some play between the scan head and the fine threaded bushing, but it’s small enough to prevent the bushing from falling out. I have however had problems with the bushing turning with the adjustment screw preventing me from adjusting it’s height. I’ll probably solve this with a small piece of tape or something similar. I do not want to glue the bushing in with any super strong, everlasting ultra epoxy as I want to be able to change or reuse it later.

As seen in the picture the bushing does not leave much of the screw to be adjusted. This is in part due to the removable adjustment knob also taking up some thread space. I might just solve this by simply not using the knob. The screw does have a hole for a hex key so that it still can be adjusted. 

I’ve also thought about modifying the adjustment knob to make it fit over the bushing. If successful, this could give me a few extra millimeters of screw to play with.

Bottom half

I have glued on a copper “scene” on which the sample will be attached. It is glued on a piece of glass in order to isolate it from the scan head body which is grounded. The tip mount will also have some glass part incorporated for the same reason. These are the most electronically sensitive areas of the build.

I have also put a similar piece of glass on the other end of the bottom plate. This one is just to get less friction between this plate and the adjustment screw.

I have also constructed small standoffs which almost looks like tiny rocks in the picture. These are made of a harder metal and have a point to them. They will act as a pivot point when adjusting the tip height with the adjustment screw. Currently they are just placed on the bottom plate, but I plan to solder them in place when I know exactly where they are going to be.

If i ever redo this part I'll need to find a good way to cut glass. I sacrificed a few micriscope slides trying to get shards of a nice shape and size.

Until Next Time

After getting the tip mount in place I can really start experimenting with tunneling current and aproach. The first thing that I'll have to do then is to make the preamp. I plan on using the same circuit as Dan Berard but with a different op amp. It will however have to wait, since I'll be traveling this weekend.