How To Pitch the Propeller

3. Slip the propeller over the mandrel with the pushing face of the propeller against the pitch block. You can adjust the height of the propeller on the pitch block by using spacers between the bottom mandrel cone and the mandrel flange. Ideally the propeller should be centered on the pitch block if it is not cupped. If the propeller has a cup you should let the cup overhand the relief area cut into the pitch block to accommodate the cup. Lock the propeller against the pitch block.

4. Use the rawhide hammer to work the propeller to the block. Start in towards the hub and work your way out to the outer edge of the propeller. Once the propeller fits within approximately an eighth of an inch from the block, you will have to use a leather belt or strap between the propeller and the block to give you a fulcrum point to bend the propeller over and overcome spring back. This will allow you to obtain a more exact fit to the pitch block. Once the propeller is laying down against the block, use the dead blow hammer to take any slight flaws out of the blade - four or five hits are usually all that is needed per blade.

On stainless or bronze wheels you can use the copper hammer to feather in the outer edges. If the propeller has a cup you can bend the cup over the relief cut in the pitch block or you can obtain a softer roll by placing the leather belt or strap under the trailing edge and bend the cup over the belt or strap.

After all blades are shaped to the block, draw a line around the best blade on the pitch block and compare the other blades to the profile.

When repairing stainless steel propellers some will require the use of heat to bring the propeller back to its original shape. When heating stainless do not exceed 1700 degrees Fahrenheit. At 1700 degrees Fahrenheit, the grain structure of the metal changes. A 1700 tempstik can be touched to the area being heated and will melt when the metal reaches 1700 degrees. You will find the heated area to e Dull Red in color, and the propeller can be worked to the pitch block. A standard oxygen/acetylene torch works quite well. This allows you to heat only the area that is bent and makes finishing the propeller much easier.

Most bronze or brass inboard wheels will bend cold. If heat is required to repair these, care needs to be taken to prevent breaking the blades.

The temperature should exceed 1400 degrees Fahrenheit before repairing. Most alloy bronze propellers are extremely brittle between 700 to 1400 degrees Fahrenheit. Use 1400 degree Fahrenheit tempstiks to check the heat before striking the propeller with a hammer. Always heat the propeller from the hub to the outer tip using a #4 or #6 rosebud torch, this will evenly heat the entire blade. Then work the blade to the pitch block using either a rawhide or copper hammer. Push the blade to the block or tap it lightly.