​Bi-Metal COBALT Hole saws
•  Full 47mm cutting depth 
•  Extra tough contruction – resists tooth breakage
•  Perfect combination with RLHD300 SPEED Arbor

HSS stands for High Speed Steel
​
Construction is Bi metal (two metals) being HSS teeth + alloy strip (blade backing).
 
The HSS and alloy strip were originally electron beam welded together but increasingly Lasers are used.
 
Only the top 3 to 4mm of a Bi metal hole saw is HSS hence the reason why the hole saws have limited re-sharpening life.
 
Cobalt can be alloyed with the HSS to make it harder and more resistant to heat.
 
However the addition of Cobalt increases costs.
 
All Re-load Hole saws include Cobalt as standard right across the range. 
 
TIPS
 
AVOID excessive speed as the heat generated will cause a loss of hardness in the teeth.
 
Use cutting compound to preserve tooth life.
 
Avoid breathing compound fumes during cutting.
 
Ideal for sheet metal, stainless, cast iron and mild steel.