Using threaded ridged forks with an a head set?

[FMJ]

The safest way to do it is run a stem that clamps internally like a Race Face EX. You don't have to worry about the stem clamping on the threads.

 

[velomaniac]

One problem you might meet is on disassembly. The AHead wedge shape washer if made of a softer plastic can deform around the threads when you tighten it down. Result is it will not come out again when you want to access the barings. Destructive removal is sometimes the only way as I found to my annoyance when I did this