Rebuilding Filaments

A project log for Hitachi S-450 Scanning Electron Microscope

Getting an old (1980s) SEM running and adding digital capture

jerry-biehlerJerry Biehler 11/21/2014 at 20:390 Comments

Filaments are expensive, around $50-55 each and you must buy 10 at a time. You can also send in your old bases for rebuild. But since I have the wire and the tools to do it myself I am rebuilding my own.

I am using an old Hughes stored energy welder and a Unitek spot welding head to make my own with the .089mm tungsten wire I bought off eBay. I use a small vise to hold a loop of the wire and then thread another loop of wire though that and pull tight with a pair of pliers. I then use fingernails to form the wire tight around the other to get a nice sharp tip. This is then spot welded to the filament base as close to center as possible.

Ideally after this you would put them in a vacuum chamber and run current though them to let them anneal and do all their moving around before you mount them in the electron microscope. That is a project for a later date.