I am convinced all MEC brown saws, of any age, make that awful grinding/vibrating/knarling sound when cutting steel. A bit like the gearbox is about to fall into pieces, new blade or not, makes little difference.( yes, clutch is adjusted tight)
On that note, I completely stripped an old one (the one with the vice that sits, and opens and closes at an angle). All bearings seem to be ok, the worm drive is ok on the motor shaft, as are the bearings. The bronze worm wheel shows slight signs of wear, but not that bad in my opinion, -the teeth are not razor sharp. The clutch cone fits nice, no sign of slipping on the dished clutch plates- So I give up, its a mystery noise.
I am unlikely to put it all back together as I have another, newer one, (which also makes these strange noises, but has a back jaw and cut part clamp) so if anyone is after any bits, let me know before it goes to the scrappy. Bob