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These checks are prioritized for the sake of practical evaluation in front of the saw’s owner.
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 Slab Sample
Figure 1
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If the owner objects to sawing a slab, or the saw is not running, ask to examine a stone recently cut on the saw. A good saw, with a true blade, produces a smooth, flat surface across the slab — and reduces your time on the wheels with a good flat back for your cabs. A stone with a rippled, layered, or warped surface may indicate a saw with a misaligned carriage feed, a warped or dished blade, or other problems.
Blade Trueness
If the saw is operable, move the carriage to the starting position, with the rock vise empty and backed off the blade. Engage the carriage drive clutch, close the lid and, if the viewing window allows, watch the edge of the blade straight on — point of view of the rock! — as it spins. Watch for side-to-side wobble as the blade spins. Ideally, the cutting edge will be thin and straight as it turns — or true, as a mechanic would say — no lateral movement. But even if there is some small play, the blade can be professionally trued later. Several manufacturers will true a bent or dished blade for a cost that is still much less than a new blade, which can easily cost several hundred dollars. [See Figure 1, right.]
Photo 1
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Blade Life
You can quickly check how much cutting edge life remains by measuring the serrated edge that contains the diamond in the blade. [See Figure 2, below] Less than 1/8" here means you’ll be replacing the blade soon — 1/4"-3/8" or so means your blade is perhaps halfway through its lifespan. More than 3/8"? You’ve got a blade that’s almost new — buy it! [See Photo 1, right.]
Figure 2 |
Oil Condition
Another clue to the saw’s maintenance is the condition of the oil. If the oil is relatively clear or even partly translucent, it may be a clue that the owner changed it regularly — indicating he may have treated other parts of his saw with care. Use a pencil, a thin dowel, or a dop stick as a dipstick to check the depth of sedimentation in the tank. Ideally, there should be less than an inch of thick mud that lies under the lighter surface oil. If you feel occasional lumps or even chunks of rock, it may mean the owner was careless with maintenance. If you can see the bottom of the tank, you may have a real find.
Motor and Belt Drive
Listen to the motor as it works . . . smooth and steady, or chattering and sparking, indicating worn armature or brush contacts? Squeaking or squealing noises from the motor may indicate worn bearings. Watch the pulley action for nice rotation, without wobbly or jumpy action. A noisy belt that has developed a lumpy bend from long term inactivity can sometimes be remedied with an inexpensive new belt. Motors on most lapidary units are pretty standard 1/3 HP 110V 1800 rpm, and can be easily found through www.eBay.com or your local paper.
Carriage Feed
With the saw unplugged and switched off, raise the hood and release the carriage drive clutch. Move the carriage back and forth along the rails to check for smooth travel. Any binding or sticking here could indicate a misaligned carriage feed — potentially expensive, if the carriage must be replaced. Then, re-engage the clutch, and check that the carriage stays in place. [See Photos 2a, 2b, 2c]
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| Photo 2a |
Photo 2b |
Photo 2c |
Arbor Trueness
With the saw unplugged, check the arbor free play, or looseness in the arbor shaft. Check for axial play by gripping the arbor pulley outside the saw, then pulling and pushing the arbor shaft in and out to see if there is play or looseness. [See Figure 3, below left] A good shaft will be tight and free of play. Check for radial play by gripping the pulley or the arbor flanges and trying to move it from side to side. [See Photo 3, below right] A good arbor with good bearings will be tight and free of play. Play in the shaft can indicate worn bearings or a bent shaft — necessitating new bearings and, if necessary, an entire arbor assembly. Restoring a worn arbor or bearings can be potentially expensive, but both bearings and entire arbor assemblies can be had, even for older saws.
Figure 3 |
Photo 3
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Tank Condition
Look under the saw’s reservoir tank . . . any rusty, corroded spots or dripping oil leaks? These, too, can be repaired, but can be a negotiating factor when you make an offer. Don’t worry too much about a seized or corroded drain plug — as I learned later, saws are better emptied from the top, since the mucky bottom layer that collects in the saw tank will hardly flow at all. —WS
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Will Shaw is a video- and multimedia-producer in civilian life. He has been a rockhound since he was nine, and enjoys slabbing & cabbing pietersite, Peruvian opal, and chrysoprase at the Searchers Gem and Mineral Society in Anaheim, CA. He also created the Web site for the Gem Art Center at www.gemartcenter.com. Will can be reached at info@digvisions.com, especially if you have any tips on polishing Yowah opal!
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