Mine does not say bi-metal on the case. This is a higher end set so they may be. The teeth are are not small, they are raked out like any wood saw. A pipe fitter once told me he never drills larger holes, always with a hole saw. If he ever uses a cutting aid it is always just soapy water in a windex spray bottle. The cutting aid is to keep the bit/saw cool, not lubricated. I have not used cutting oil since he told me this, and never have had a problem. Lowes always has the Lennox brand in stock here in Pa.