Configuration of buffer weights

**prepare** · 04-08-22, 08:23

Originally Posted by lysander

Black oxide vs black phosphate.

If your dealing with quality spring pins, you are dealing with either ASME B18.8.2 or NASM16562 spring pins (tubular slotted). The two specifications are comparable in regards to strength, and quality. The major differences are B18.8.2 has more sizes available and the finish specified.

NASM16562 allows three types of finish, phosphate, cadmium, or passivated CRES. B18.8.2 does not specify any finish, allowing the purchaser to request any finish desired. Normally, for steel pins, that black oxide.

B18.8.2 also discusses beryllium copper spring pins.

Is phosphate superior to the ASME B18.82 finishes?

**lysander** · 04-08-22, 08:52

Originally Posted by prepare

Is phosphate superior to the ASME B18.82 finishes?

Zinc phosphate is generally considered a better finish for resisting corrosion than black oxide. But, it is not like it won't rust at all.

But, like I said B18.8.2 doesn't specify any finish, so you can find B18.8.2 pins with a phosphate finish.

**Curlew** · 04-08-22, 14:20

Originally Posted by lysander

Because the FA pawl is under a fairly high load they needed to ensure that the pin actually spanned the gap. The pawl gap is 0.155" wide, and is you push a 0.25 long pin flush to the side of the plunger you are only engaging the tapered edge of the pin. You can have no engagement at all if the pin is at the short end of the tolerance.

Thanks for the explanation. I just examined a forward assist, and I can see what you’re saying here.