[dlavery]

The type of pin that you have been discussing (running parallel rather than perpendicular to the shaft) is commonly known as a "Dutchman Pin." They are commonly used to attach large flywheels to drive shafts. Dutchman Pins have two distinct advantages over "conventional" pins, in that they are typically much stronger for a given pin size, and they require less material to be removed from the parent shaft - thereby leaving the shaft stronger (as with conventional pins, the diameter of the Dutchman Pin should not exceed 25% of the diameter of the parent shaft).

The shear strength of a conventional pin is calculated as: Pin Shear Strength = 2 * Pi * Pin_Radius^2 * Material_Shear_Strength

The shear strength of a Dutchman Pin is calculated as: Pin Shear Strength = Pin_Diameter * Pin_Length * Material_Shear_Strength

In a typical application where the pin is 25% of the shaft diameter, and the hub length (and therefore pin length) is the same as the shaft diameter, the Dutchman Pin will have a shear strength 250% higher than a conventional pin. For example, lets assume we want to attach a wheel with a 1" long hub to a 1" diameter shaft and a 0.25" diameter pin. The pin is made of tool steel with a shear strength of 45,000 psi. In this case, a conventional pin would shear at 4418 pounds, while the Dutchman Pin would survive past 11,250 pounds of shear force.

As the strength of the pin is determined by the total cross-section area of the pin, you typically do NOT want to use a bolt or threaded fastener as the pin. For a given diameter pin (as measured across the threads) the threads reduce the effective cross-section of the pin, thereby reducing the pin strength.

Dutchman Pins also offer some advantages over square keyways and keys, such as easier manufacturing (in some cases) and fabrication with more commonly available materials.

-dave

p.s. you can indeed broach a square keyway in a blind hole, it just takes a different technique than using a conventional broach set.