[Dave Bilyk]

Thanks guys,
I will double check for burrs, particles, but have already been careful.

Jim, you said alloy, so that is another option, were the alloy ones you used with or without rubber inserts?

Randy, I annealed with a similar method, I put the washers on to a piece of thin steel plate and heated until the washers were dull red then dunked them. I think the anti sieze is a good idea, I will use that as it will help increase the crush for the same torque, and probably give a better feel when tightening.

One point is that the tapped hole and the sealing face need to be really square, the higher the tolerance or actual error, the more crush is needed to seal, also it is something that is very difficult to check in manufacture, so it probably isn't.

I'll try new annealed washers and anti seize next.