What material and process is best for making compass needles?
We are making some compasses to spec, but are stuck when it comes to the needle. The spec does not designate the material, just that it needs to be magnetic. Does anyone know a source of info, or have info, on how to make them?
So far it seems they should be 1010 CRS, magnetized when hot. Supposedly they need to be low carbon so they don't harden when coming down from austinizing temperature. But that's just a guess.
We'll stamp them (or machine them if necessary). But we're looking for the correct material and magnetizing process, and perhaps a gauss spec.
PS: This is posted somewhere else, in a private forum. I thought I could post here as well because of the odds being very slim that one person would see both posts. If someone here is a member of the private forum, I apologize for double posting.
This is a shot in the dark, but I think you would want something with a high magnetic coercivity and a much higher magnetic remanence. I did 10 minutes of research in the Handbook of Chemistry and physics and the wikipedia on magnetic coercivity and I think that what you want is probably one of the Alnico technologies. They are likely to perform orders of magnitude better than 1010.
You might try asking an apps engineer at http://www.dextermag.com/ as they make alnico which I think is probably a good choice.