Washers - NAS1149F0 vs AN960
 

OK, I am confused.

In Van's instructions (Section 05-33) it clearly says to NOT substitute a AN960 washer for a NAS1149 washer because the NAS washers are manufactured to a higher tolerance but when I try to buy NAS washers from Spruce they offer the 960 washers instead.

Is this a concern?

thanks,

bruce

The main concern is in situations where the plans call out the use of washers as spacers......

Even though both washer designations are aircraft grade hardware, the NAS part has a much tighter tolerance for thickness than the AN washers have.

This causes a lot of problems when calling out a specific # of washers for an assembly that they are used as spacers in.

So in instances where you are just using a washer for the common purpose of load distribution and abrasion protection AN960's are fine, but NAS should be used when it looks like a specified stack-up is dimensionally sensitive.

I measured a couple batches of AN960 (one from ~1983 and one from last year from AS) and the NAS1149 washers supplied by Van's. The AN960s came in consistently 0.002-0.003" undersized at 0.060-0.061". The NAS1149 were 0.0063-0.0064". n=5 from each batch.

Interestingly I also have mixed in with the old batch of AN960s some washers that have a silver-colored plating (nickel?) and match the NAS washer thickness.

Hi Scott,
I'm trying to cross reference the 5702-75-060 and 5702-95-30 washers and it appears this may be a Vans part number. Is there a better part number to cross reference? I have a big order going to Spruce for other stuff and wanted to include those. It calls for them on the RV-4 blueprints on drawing 28.
L. D.

I think someone figured out years ago those aren't *actually* "washers" in the AN/NAS sense...they're *spacers*.

Would it make sense to use stainless washers on the aileron and flap hinges?