sheaves arc tight on their shafts. Then chcck them for alignment (by laying a straightedge across the pulley faccs).
If you have a mechanical variable-speed system, adjustment is not so simple. Variable-pitch sheaves move when speeds arc adjusted, making simple eye-balling difficult. I suggest you consult the owner's manual or call the manufacturer for specific instructions.
On rare occasions a pulley sheave will be out of balance. Suspect this only when you have exhausted other possibilities. You can check the pulley by mounting it on a separate motor to sec if
Indexing only. The indexing pin (on left end of housing) allows you to lay out turnings in quadrants for decorative work. The pin is fragile and should never be used as a spindle lock.
lathe's shaft is a serious problem, and should be eliminated. Bearings arc relatively easy to replace but replacement shafts arc expensive, often costing more than $200.
While we're still on the shaft, take a look at the business end (the inboard end). Damaged threads can be freshed out with a die that matches your thread size. If your center wobbles around in the spindle, the morse taper may be worn or damaged (first make sure the taper on your spindle and center are the same size). A damaged taper can often be remachined.
The Drive System—A well-adjusted drive system should produce minimal vibration at all speeds. To chcck your lathe, let it run free, and place your hand on the headstock cover (not the belts). If you find yourself getting a free massage, it's time for adjustments.
The problem here is usually excessive vibration from some part of the drive that's out of balance or alignment. Since most lathes are belt-driven, start by checking that all pulley sheaves are properly aligned and that belt tension is correctly adjusted.
Simple step-pulley systems work much like a bicycle's gears, except that you have to stop the lathe to change speeds. First, visually inspect your pulley sheaves: Most stepped pulleys are made of aluminum and can crack or separate with long use. Make sure your pulley it vibrates.
Sometimes you'll need to view the system while it's running to help pinpoint the source of vibrations. Caution: Be exceedingly careful not to catch your hair, clothing, rags, tools or body parts in the belts.
A vibration can often be traced to a motor-mounting problem. Bolts tend to loosen, allowing the motor to vibrate against the belt. This can set up a sort of harmonic "thrumming" that can make you crazy. Chcck the bolts, and also the hinge on the motor plate if your lathe is so equipped. If your system has an idler shaft, chcck it for play and alignment as well. Be sure to lubricate the pillow blocks on such an assembly regularly.
Don't forget to chcck the belts themselves. Worn, frayed belts should be replaced immediately. On older lathes, belts may have been replaced with the wrong size. Drive sheaves have a certain pitch angle, and improper belts won't fit correctly. Belt lengths can also be critical, especially on mechanical variable-speed systems. Check your manual, or ask the manufacturer for the proper replacement belt. Variable-speed systems often have matchcd belt sets, much like a tablesaw. If you must replace one replace them all at the same time avoid problems.
With older machines you're often your own when it comes to finding parts or information. Ask the advicc of a machinist or a good drive-system specialist (Washington Drive Systems, 2755 Airport Way South, Seattle, WA 98134).
Finally there's the indexing system.
Center to center. The headstock and tailstock spindles should meet point-to-point. Poor alignment will mean limited accuracy in operations such as boring.
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