Sand is mostly silica and does NOT conduct electricity.
If you must use an abrasive on the points make sure the grit is made of a conductive material. This is the main reason why a points file was developed as THE tool to recondition point contacts.
FYI
Cheers,
Sorry for the thread-jack, but I'm curious about conductive grit. What sort of material is this, and where can I find it?
I don't recommend (or use) grit material for points anymore, as when I did, the points burned far faster. When I found documentation from the telco company about point reconditioning (the telephone exchanges used to have quite a lot of relay point contacts). They found out through experience that grit was very, very bad for points longevity. And, their technicians made use of ONLY point files made for that intended purpose for correcting "bad connections". (I believe it was a Bell Labs investigation/report. But, it has been many years since I saw it).
Pretty much all the cheap, commonly available "sandpaper" types have non-conductive grit. Aluminum oxide worked best for me. But, I speculate it had grit binder that was tougher, and then left tinier particles that wore off quickly, even though they were non-conductive.
But, probably the best chance of conductive grit would be silicon carbide. I've not tested that though. I just don't have probes that small, and wouldn't expect the grit binder to be conductive.
I very much doubt much attention is made toward purposely making the grit conductive during manufacture. More like, "it is what it is, and it will make your wood smoother." I wouldn't expect "conductivity" is part of their process control.
Like many things, there is the proper tool for the job. But, screwdrivers are used as pry bars and their handles are still used as hammers, perhaps daily.
Cheers,
