Aluminum Thread Galling?

[Noah]

I'm assembling the aluminum AN fitting into the aluminum brake caliper, and the fitting seems to be galling, even though I'm using PST. I think it only had 1 or 1-1/2 turns before being finger tight, and maybe one turn with a wrench and it is REAL TIGHT. I have used a lot of NPT fittings over the years, but mostly steel, brass, and stainless - not much aluminum. I'm not used to seeing so many threads remaining exposed. or in having things tighten up so quickly - is this OK? Are there any specs defining acceptable number of threads showing for aluminum AN fittings?

Thanks,

[G-force]

Either the fitting was machined oversize, or the hole in the caliper was tapped undersize. Even dry, it should finger tighten about 1/2 way in.