Rotary Broach Tool

grabcad

Using ER20 collets and commercial collet holder. 6204 and 30204-A bearings. Back seal of the 6204 removed and a grease nipple provided to inject grease between the bearings.The broach protrusion is adjustable to accommodate different broaches lengths. This is achieved via a set screw at the steam and a rod. Not shown in the model is a ball bearing ball between the broach and the rod. The body is the only more demanding part. It is turned with the bore concentric and undersized. The bore is then bored to size and depth and at the correct angle (1.8 degree in this case).The geometry is such as to make the tip of the broach intersect the rotation axis and thus to give the broach tip the wobbling action without rotation. While most tools are using fixed length broaches, here any length (an diameter) can be used and adjusted to protrude the correct amount.A more common design has the body bolted out of two parts, but I feel this form is safer to use without protruding edges and bolts.