Elmo wrote:
(snip)
Echo HC150 Hedge trimmer:
Is it "normal" for the sliding blades to bind every hour or so,
necessitating loosening of the bolts spaced every six inches or so?
(snip)
b) I'm not sure what's happening with the hedge trimmer; why are the nuts
tightening up in use? Is that what happens with hedge trimmers?

Have you tried new locknuts?

Are you following the blade cleaning & lubrication recommendations?