CrushGrind Forster Drill Bit 4 Set

Tungsten Carbide Forstner Style Bit Set.
Tungsten Carbide tips stay sharp longer than HSS as they resist wear. They are less likely to heat up during use and run at higher speeds than traditionally recommended for HSS bits. The speed on the hardwood 400-600 rpm speeds between 800-1000 rpm can be used on softer woods while achieving a good, clean cut. 
(Daves top tip, just remember stop lathe before pulling the 42mm bit out to reduce marking and making it easy to sand.)
This set contains the 4 diameter bits required for making both the CrushGrind Diamond shaft (195mm, 260mm & 470mm) and the shaftless Diamond Wood mechanism which is shaftless!
The 22mm diameter is for the stopper fixture at the top of the Diamond Shaft mechanisms.
The 26mm diameter is for the cavity for both Diamond Shaft & Diamond Wood.
The 38mm diameter is for the grinding mechanism for both Diamond Shaft & Diamond Wood.
The 42mm is for the opening of the grinder for both Diamond Shaft & Diamond Wood.
These self centering woodworking Forstner bits are carbide tipped to cut cleanly through end  them perfect for pepper and salt mills with minimum sanding.
The shaft diameter for the 22mm, 26mm, 38mm, 42mm it is 10mm.