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Problem:

Reoccurring pulsation complaints (high speed pulsation occurring after 3,000 to 6,000 miles)

Cause:

Bench lathe induced runout

Solution:

Preventing the majority of bench lathe setup problems is a relatively easy process. It involves the following steps:

  1. Arbor Shaft Runout: Measure arbor runout and correct if necessary (Figure 26.1). The typical specification for arbor runout measured near the end of the arbor is .002”. If the runout is outside of acceptable, remove and clean the mating surfaces. If this doesn’t correct it consult your lathe manual.

    Figure 26.1 Arbor Shaft Runout

  2. Arbor Face Runout: Measure the arbor face runout (Figure 26.2). The typical specification for this measurement is .0005”. Correction of excessive arbor face runout will have to be performed using the lathe manufacturer’s procedures.

    Figure 26.2 Arbor Face Runout

  3. Hubless Adapter Arbor Mating Surface: The adapter show in Figure 26.3 is typical in many shops. Hubless adapters rely on the mating of the surface shown in Figure 26.3 and the arbor face to be accurate and true. With the buildup shown in Figure 26.3 it would be impossible for an accurate setup with this adapter.

    Figure 26.3 Dirty Adapter Face

  4. Correcting Arbor Mating Surface: To clean the small mating surface, place a piece of sandpaper on a flat surface and run the adapter’s small face up and down a few times while applying even pressure. The end result should look like Figure 26.4. Don’t worry about pits or indentations, these won’t effect the mating.

    Figure 26.4 Clean Adapter Face

  5. Indexing Adapter to Lathe: (This step is optional if the arbor face runout was .0000”.) If the arbor face runout was greater than zero then the hubless adapters will have to be indexed to the lathe before continuing. Some adapters have index marks cast into them while others don’t. If there is no index mark use a file to make an index mark on the edge of the small mating surface as shown in Figure 26.5.

    Figure 26.5 Adapter Index Mark

  6. Preparing Adapter for Machining: Install the adapter on the lathe and position the twin cutter to enable machining of the large mating surface as shown in Figure 26.6. Sometimes it will be necessary to remove the opposite tool holder to achieve the proper clearance.

    Figure 26.6 Twin Cutter Setup

  7. Machining Large Mating Surface: Remove only as much material as necessary to achieve a 360 degree cut. This usually only requires .002” to .005”. Make a slow cut to machine the large mating surface. This process makes this mating surface true to the lathe as shown in Figure 26.7.

    Figure 26.7 Finished Product

  8. Optional Adapters: The same procedure can be used on the optional adapters available for most bench lathes such as the composite rotor adapter shown in Figure 26.8.

    Figure 26.8 Other Adapters

The average bench lathe setup will take between 1 to 2 hours to perform the procedures listed above on all the adapters in the shop. Once this procedure is performed all that is necessary it to keep the small and large mating surfaces clean and free of nicks and burrs. If the arbor face had runout and index marks were used then the adapter and arbor index marks should be aligned each time the adapters are used.

Even after this procedure has been done it is still necessary to check the setup. This is done by performing what is known as “scratch cut”.

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