Howdy,
Ok guys, you asked! Here is the scoop on stellite (hardfaced) bars vs. sprocketnose:
First of all there is not a black and white world here as there are significant differences within the two types. As a rule, the sprocket nose bar will give you more available cutting power out of a given unit. Generally, this is most obvious on small highspeed saws, and less obvious on large high torgue saws, which is one reason why stellite bars are the design of choice in jungle markets. The stellite bar may be of two types: those that have the nose torch applied as a deposit, and then ground to shape, and those that have a preformed stellite deposit stitched on there, such as "Laser Weld". The torch weld bar is easier on the chain bottom wear wise, due to the microstructure alloying the chain to slide over smooth carbides. The preformed type has a carbide structure that is granular and angular therefore eating into the part bottoms to a greater degree. The sliding chain of course generates heat, and the faster the saw and more unequal pitch the chain, the greater the heat.
The sprocket nose bar lifts the chain off of the nose onto a sprocket for the turn around the nose on bearings. Less friction, but the lift off means it is a nasty situation when the chain tries to derail, which happens easier because of the lift-off to begin with. Kickback is higher on a sprocket nose of the same nose radius as a stellite bar by comparison. On a saw in the 60cc class or smaller the cutting performance difference is significant, as much as 25%.
Nose sprockets are of two major different designs, one has the tips coined or ground from the sides, so the chain can step off without damaging the starwheel/outerrace. The other has square sided teeth, and these seem to have a habit of breaking nose starwheels for those people who frequently derail chain.
It gets worse from there.
Regards,
Walt Galer
