large bell, hoe, spade
鎛 centers on a large metal object: a large bell, or a heavy metal farming tool like a hoe or spade. The common thread is a substantial metal implement.
鎛 combines 金 (metal) with 尃, which likely contributes the sound. The character originally referred to a large metal bell or a metal farming tool.
The left side is metal 金, and the right side 尃 looks like a spreading shape. Picture a large metal bell spreading its sound, or a wide metal hoe spreading soil.
For ハク, imagine a large bell being struck with a hack: hack -> ハク, and the metal bell rings out.