Daniel Wrote:
the double coil spring washer
This washer is called a Thackery Washer and is quite different to a spring washer, notwithstanding that at least one of the Parts Sellers were offering a Spring Washer with an extra helix as a Thackery Washer.
A Thackery Washer has a Joggle in the flat wire from which its made, where the ends of the wire fall slightly short of lining up. This joggle allows the faces of the Thackery Washer to remain parallel even when fully compressed and effectively, the Thackery Washer is only two thickness of wire for its full 360 degrees.
Without the joggle, the washer will be three thicknesses of the wire where the end nearly meet, and only two thicknesses elsewhere.
Regards,
Bill