Sorry to say it is usually headstock bearings. It might be a loose pulley
knocking on the key. But even if it is, by the time you get the thing apart
to fix a key properly you might as well replace bearings while you're at it.

Good luck,

--
********
Bill Pounds
http://www.bill.pounds.net/woodshop


"william kossack" wrote in message
news:K2OTb.213579$xy6.1102525@attbi_s02...
I have a grizzly g8691 lathe.
It seems to work OK but at higher speeds it produces a knocking noise.
I'm going to try and take the cover off this weekend if I get the time
but I'm wondering what the noise could be?