I don't know the values, but easy enough to test. Using a plate of each (might be difficult to find for the forging), 1/2-inch or so thick, clean the plates with an aromatic solvent and then anchor one of the plates in a jig made of plywood such that the surface of the plate is above the surface of the plywood. Place the other plate on top of the lower plate, then place a 50 lb. weight on top of both plates. Using a dynamometer to measure the force, pull the top plate across the fixed plate until it just starts to move. Do this in four different directions, to negate minor surface differences. The coefficient of friction is the ratio of the normal force (50 lb.) to the force required to overcome static friction (the force measured on the dynamometer). If you don't have a calibrated dynamometer, use a fish scale with a capacity of at least 200 lbs. Repeat the test with a thin film of water, then with a light oil and compare the values.
Thanks. The best I can find in reading so far is a range of .08 to .30, .16 being a good average value for the coeficient of f between the forged, normalized and tempered alloy carbon steel, and the bearing material of bronze casting.
