Chapter Four - The General Preparation

STEP IV-3: Enlarge the seat tube and down tube sockets in the bottom bracket shell by grinding with a die grinder. When clamping the bottom bracket shell in a vise, as shown in Figure 4-5, make sure to use soft jaws in the vise so as not to damage the faces or any of the threads. Again the fit should be loose; if the seat tube is inserted into the socket in the bottom bracket shell, the top of the seat tube should wiggle back and forth about 3" (The chain stay sockets will be enlarged later.)

FIGURE 4-5: Using soft jaws to clamp the bottom bracket faces

FIGURE 4-6: Grinding out the inner diameter of the fork crown

STEP IV-4: Enlarge the inside diameter of the steering column hole in the fork crown. This can be done with an 8" half round file, a Chadwick # 28 reamer, or a die grinder as shown in Figure 4-6. This joint should also be loose; the crown should easily slide down the steering column under its own weight. It should also wiggle slightly. In the case of a crown with a lip, use a die grinder to open up the inside diameter

STEP IV-5: File and sand the outside edges of the lugs, fork crown, and bottom bracket shell. All deformities, burrs, irregularities, and forming marks should be removed during this procedure. Do not touch the bottom bracket faces, the fork crown race seat or the head set seats on the lugs at this time! It is not necessary to do anything to the top surface of the seat lug at this time either. Roughing work can be done with a Nicholson 8" half round file.

FIGURE 4-7: Finish filing can be done with jeweler's files or rifflers

FIGURE 4-8: Sanding lugs with 1" wide emery cloth strips

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