panamark
fully equipped rock polisher
Member since September 2012
Posts: 1,343
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Post by panamark on Jun 3, 2014 8:37:24 GMT -5
I am about to finish the rebuild on the HP 20" saw, but I have one more question. What size and type pulley goes on the motor shaft end? It looks like it should be about 3-1/2" but I see on one HP parts site they have a 3.35" for the 18" and a 3.55" for the 24", but they don't list what the 20 " saw would use. I have bought a real nice used motor (1725 rpm) that is just waiting to be connected. I will add pictures to my other rebuild post when I get it finished.
Thanks for any help.
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,634
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Post by QuailRiver on Jun 3, 2014 16:56:47 GMT -5
My 20" Covington Saws have 2-1/2" motor pulleys and 6" Arbor pulleys. Larry C.
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Post by Rockoonz on Jun 3, 2014 21:50:57 GMT -5
To have a 3.5" arbor pulley they must use a 1.5" motor pulley to get about 740 rpm for the old style blades they had back then. For a 303 or any sintered blade I would use a 2 inch pulley on the motor with 3.5 on the arbor to get about 1000rpm. Larger pulleys are better, belt is less likely to slip and belts last longer.
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,634
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Post by QuailRiver on Jun 4, 2014 0:08:37 GMT -5
To have a 3.5" arbor pulley they must use a 1.5" motor pulley to get about 740 rpm for the old style blades they had back then. For a 303 or any sintered blade I would use a 2 inch pulley on the motor with 3.5 on the arbor to get about 1000rpm. Larger pulleys are better, belt is less likely to slip and belts last longer. Yes the new blades can turn faster rpms. But if he changes the motor and arbor pulleys to increase the rpms from the 700s to the 1000s, since the powerfeed pulley is also attached to the arbor pulley that is going to increase the freed rate by the same % as the rpms have been increased. So then he will also need to change the powerfeed pulleys to slow the feedrate back down to a normal speed. Larry C.
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panamark
fully equipped rock polisher
Member since September 2012
Posts: 1,343
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Post by panamark on Jun 4, 2014 2:55:27 GMT -5
Thanks guys! I appreciate the info. I did find more good info online in the Diamond Pacific catalog that gave me the desired RPM for the blade as well as the formulas and a table for pulley combinations. The saw has a 1" arbor shaft with a very serviceable 4" pulley on it. So to get the desired speed on this 20" blade of about 850 rpm I calculate I need a 1.75" motor pulley. (the motor is 1725 rpm) I understand that a bigger pulley would function better, so other option is to increase arbor pulley size. But it probably is 6's in terms of money spent. If I see belt wear and slippage problems, I will have to reassess.
The powerfeed takeoff pulley is a bit of a problem as it is hard to find a replacement 2" pulley with a 1" bore. Almost impossible to find, so I am going to go up to a 2.9" pulley here and use the 3 stepped pulley on the feed screw drive to adjust feed rate.
Maybe soon I will have the saw slabbing.
Thanks again.
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