Threaded aluminum steerer?
 

I've heard of people buying 1inch threadless forks with steel steerers and getting them cut and threaded for threaded with no problems. I'm wondering if it would be safe/possible to do the same with a fork using an aluminum steerer. Thanks

Not something that I would do, nor would I seek the advise here about issue that involve my safety. If you find a local frame builder, or some who really knows what they are doing, ask them.