Bench Lathe Adapter Solution
Preventing the majority of bench lathe setup problems is a relatively easy process. For example, follow the following steps.1. Arbor Shaft Runout
First, Measure the arbor runout and correct it if necessary. Typically, the specification for arbor runout near the end of the arbor is .002". However, if the runout is outside of the specification, remove and clean the mating surfaces. If the problem persists, consult your bench lathe manual.
2. Arbor Face Runout
Second, measure the arbor face runout. Usually, the specification for this measurement is .0005". If the measurement is off, a correction will have to be performed using the bench lathe manufacturer's procedures.
3. Hubless Adapter Arbor Mating Surface
In some cases, you'll come across adapters like the one pictured below. This adapter is typical in many shops. These kinds of adapters rly on the mating surface as well as the arbor face to be accurate and true. Because of the state of the one pictured, it would be impossible for an accurate setup with this adapter.
4. Correcting Arbor Mating Surface
In order to fix a mating surface, it will have to be cleaned. To do so, place a piece of sandpaper on a flat surface and run the adapter's small face up and down a few timers while applying even pressure. As a result, you'll end up with something resembling the image below. Likewise, it is important not to worry about pits or indentations as these won't effect the mating.
5. Indexing Adapter to Lathe:
(This step is optional if the arbor face runout was .0000".) Next, if the arbor face runout was greater than zero, then the hubless adapters will have to be indexed to the lathe before continuing. This is important because some adapters have index marks cast into them while others don't. As a result, 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 the image below.
6. Preparing Adapter for Machining
Next, install the adapter on the lathe and position the twin cutter to enable machining of the large mating surface as shown below. At times, it will be necessary to remove the opposite tool holder to achieve the proper clearance.
7. Machining Large Mating Surface
Next, remove only as much material as is necessary to achieve a 360 degree cut. Typically, this only requires .002" to .005". Make a slow cut to machine the large mating surface. As a result, the mating surfaces becomes true to the lathe as shown below.
8. Optional Adapters
Similarly, the same procedure can be used on the optional adapters available for most bench lathes such as the composite rotor adapter shown in the picture below.
Conclusion
The average bench lathe setup will take between 1 and 2 hours to preform. Once this procedure is performed it will become a simple matter of keeping the mating surfaces clean and free of nicks and burns. 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 completed, it is still necessary to check the setup. To do so, you'll need to perform a scratch cut.
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