This is when we fit our pump or motor to have either a splined or keyed hub instead of a shaft. The key width is also specified and the depth is ½ of the width. Each one specifies the shaft diameter, shaft length and total length. These shafts come in letter sizes A, B, C, D and E with double letters AA, AH, BB and CC. A stepped key will adapt between a shaft and hub of different sizes. As with anything, you can actually have many sizes and variations of each one including oversized, undersized, stepped, and high profile. The keys can be rounded (shown on shaft), square or a ‘woodruff’ cut (shown). If you are designing a shaft or hub for a key, be sure to consult your Machinery’s Handbook for tolerancing guidelines. If the key is smaller, it won’t be able to transmit the rated torque. To put it another way, if we enlarge the key, the shaft will be inadequately designed. The intent here is to offer the maximum strength on the shaft while balancing the shear stress on the key. Keyways are designed in proportion to the shaft diameter. Rolled edges from a broken key simply will not work correctly and must be replaced. Also, if your key breaks, be sure to inspect the shaft and hub for damage.

Keys are made of high strength steel, so if the key does break, diligently inspect all aspects of the system before replacing. The main purpose of a key is to transmit torque, but prevent larger component failure when things go wrong. This assembly is then inserted into a hub. A keyed shaft has a small recess where a key is placed in. We are probably all familiar with keyed shafts because this type is predominant in the industry. Shafts come in two varieties: Keyed and splined. However, there are three options to get great alignment with a pump or motor. This is not ideal and will definitely wear out the spider coupler faster. Each loading of the jib changes the alignment if only for a few seconds. Even if we get all of these things perfectly aligned, which didn’t happen, if the jib is loaded to this side, the stiffness of the frame causes these to shift.Washers were used to shim and they have discrete shimming heights which limits adjustment.

The aligning of the shafts is entirely done by positioning the engine.

As temperature and humidity change, so will the height and angle of the engine. The motor is mounted on a piece of wood.The pump (left) is mounted on a thin piece of flat steel and cannot be adjusted for angularity.The example here, a log splitter, is almost exactly how not to do this. It can mean the difference between a long-lasting system and one that constantly needs maintenance. Keeping your pump and motors on the same center and parallel is critical and often difficult to do.

Sae 6b spline motor