I failed the nickel test on startup of my Jet JWTS CS 240V saw. It gives me a bit of a bang when it starts from the torque which causes the nickel to fall. Do most properly setup 240V saws pass the nickel test? I could see how a 120V would take longer to spin up and perhaps have less of an initial jolt. Just curious...
my 1948 unisaw passes the test on startup and shutdown about 50% of the time. if i set the nickel up while its running it will stay there till i move it. i've even cut some 6/4 oak while the nickel was there. it stayed there..... skeez
Induction or universal (brushed) motor ? Most cheap saws use brushed motors, because of their high start-up torque. They're stable when running, but they make one hell of a bang when they start.
The "nickel test" means little when the saw is running idle. A really stable saw is one that doesn't vibrate, even during a heavy rip.
-- Do whales have krillfiles ?
This is not due to running the saw at 240volts as opposed to 120volts. The voltage that is applied to the coils of the motor is the same no matter which way you wire it. The vibrations that cause the nickel to fall are due to imbalances somewhere.
Try taping 5 pennies together. Most saws will pass this nickel test.
Frank
Frank wrote:>Try taping 5 pennies together. Most saws will pass this nickel test.
ROTFLMAO! Someday, it'll all be over....
I have a new Jet 14 inch @120V with a 1HP motor. It would not pass the nickle test until I changed the stock belt to a nylon link belt. BIG difference, very smooth, and passes the nickle test at start up about 50% of the time.
Kevin B
no way man. the nickle has to remain standing through start up, while cutting and during shut down to recieve wreck certification. havent you read the nickle test spec sheet? Bridger
My PM66 passes the nickel test, now and ten years ago. A 240v motor will have a smoother startup than a 120v. I tried the nickel test on my Delta 16.5" drill press and the the nickel rolled off somewhere and never did find it. Did not try the test on my DJ-20 (yet), but it's a very smooth-running machine.
Nickle test - bah! Now the dimes test, one near the front corner of the table, square to the blade, and one on the far corner paralleling the blade. Definitely helps to have the table top level to begin with and the more mass you've got the better. Robland's X31 weighs about 1100 pounds, probably 100 lbs of that being the three, 3 hp TEFC motors. When one starts up you can hear the "kick" but can't feel it. Of course there's a lot more set up time on a combi but once they're tuned they stay that way.
charlie b
I have a three year old Jet Cabinet Saw (Left Tilting - 3HP). The nickel rotates 5 degrees counterclockwise each time I start it, but remains standing.
Try a different nickel, the first one I tried was so chewed up it wouldn't stay standing with the saw off.
Joe
I don't have a unisaw, but my HF saw passes the nickel test. Even during start up, or shutdown. Haven't tried it while cutting wood tho. I didn't have a nickel, sot used 5 pennies. They wouldn't stand up, but lay flat OK. They stayed on the saw, no prob, altho they did move around a bit. I was doing it right, wasn't I?
I haven't tried the nickel test on my new Grizzly yet. I have to build a jig to hold the nickel for the crosscut. Oooooooooooohhhhh...
I can't try the nickel test. After shelling out the bucks for a table and planer within 3 mos. of each other I don't have a nickel left to test with. If you guys can all send me some I'll be sure to let you know how it all turns out!
Haha Joe. I'll send you a nickel.
I can stand the nickel while its running. Its actually super smooth while running and cutting. I wonder if a nylon link belt will reduce the jolt of startup? The jolt is pretty violent! Actually a lot of the noise and extravagance of it may be the blade guard rattling around on the table - its connected pretty close to the motor mount.
Thanks for the replies.
My General starts with an authoritative jolt, and it's pretty much immediately up to 4000 rpm. That's with a heavy WWII, and the heavy cast iron moving parts this saw is equipped with. Once it's running, I could probably stand a dime on edge, so I don't worry about it.
AFAIK, electric motors develop max torque at 0 RPM, so I kind of expect the jolt on large motors rated for continuous HP connected to heavy moving parts. My smaller DC, contractor's saw, jointer, drill press, etc... motors have less of a start-up jolt, so I always thought of it as a horsepower and mechanism weight thing.
The jolt could also be related to the size and quality of the starting cap.
FWIW, the General has a noticeably smaller jolt when starting with a very light blade. I would also imagine small wiring, even if technically correct, would lessen the jolt.
Barry
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