I picked up this lathe a few months ago, been slowly getting it tuned up.Correct me if I'm wrong, but did the manufacturer label the A - B pulleys backwards on the cover plate? The machine has the larger pulley on the left(outside) of the shaft(see pic), the diagram shows it to be reversed. The RPM #'s on the chart don't seem to be correct.The motor pulley that came with the lathe is the wrong size(too small) and it's only a single pulley, I'm trying to figure out the correct double motor pulley to buy(or make).Starting at the motor and working toward spindle RPM...I did some math... with the motor running at 1725 RPM.The large motor shaft pulley(the one I will make)dia. of 4.0 inches.The machine pulley(the smaller one, A and B are switched) dia. of 4.675.Pulley "F"(labeled by me in pic) dia. of 4.450.Pulley "C" at a dia. of 5.250.I get a spindle speed of 1251 close to the chart at 1250 RPM(AC).I get a spindle speed of 534 RPM using a 2.1 dia. motor shaft pulley going to a 5.750 machine pulley(A/B). I don't have an RPM tool to physically measure the RPM.It looks a little difficult to switch the A and B pulleys around, Il'll have to remove the entire shaft, I'd rather just mount/flip a new motor shaft pulley with the corresponding diameters on the correct A/B pulley. Are my calculations correct?Any help here would be great. Thanks....!!!
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IL' help here...! Anybody...???
Reply:It looks like someone may have replaced the motor and been running with the single belt, possibly using a VFD for speed control. Is the motor original? Does it have a VFD?
Reply:Motor has been replaced, no VFD, just one speed on motor 110 volt, 1725 RPM on/off. Well, looks nobody's going to chime in here with an easy math formula for pulleys/rpm. Guess I'll make a double pulley for the motor with one at 4.0 inches and the other at 2.1 and see how the rpm's are at the chuck, trial and error. Where can I get an RPM reader/meter? What kind? and how much are they?....Thanks again....
Reply:electronic tach's are pretty cheap. You can also find mechanical tach's dirt cheap. They usually have a reduction system where the number of revolutions on the tach are multiplied by 4 or 6 to get the actual spindle rpm.
Reply:I believe even Harbor Freight sells electronic optical tachsBacked my CATMA over your CARMA oops clusmy me What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:Originally Posted by ZZWELDMotor has been replaced, no VFD, just one speed on motor 110 volt, 1725 RPM on/off. Well, looks nobody's going to chime in here with an easy math formula for pulleys/rpm. Guess I'll make a double pulley for the motor with one at 4.0 inches and the other at 2.1 and see how the rpm's are at the chuck, trial and error. Where can I get an RPM reader/meter? What kind? and how much are they?....Thanks again....
Reply:This should help you out ! http://www.blocklayer.com/pulley-belteng.aspx
Reply:Originally Posted by ZZWELDMotor has been replaced, no VFD, just one speed on motor 110 volt, 1725 RPM on/off. Well, looks nobody's going to chime in here with an easy math formula for pulleys/rpm. Guess I'll make a double pulley for the motor with one at 4.0 inches and the other at 2.1 and see how the rpm's are at the chuck, trial and error. Where can I get an RPM reader/meter? What kind? and how much are they?....Thanks again....
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forhire: Thanks for confirming the manufacturer printed the chart wrong. There's no way the "A" pulleys can go faster than the "B" pulleys according to the chart. I used the same link and #'s you did to get the rpm's. I'll make a double pulley out of aluminum and check the rpm's at the chuck. One issue I may have is tightening 2 belts with one lever, I hope it tightens both belts on the 4 inch pulley and both belts on the 2.1 inch pulley. The first belt goes from motor to A or B then the second belt goes from F to C, both get tightened with one lever. May have to have a second belt handy to change out if there is a tightening issue. Once I run it and confirm the chuck rpm's with a reader, I'll make an new correct chart/pulley diagram and cover the old one up. It's much easier to make a double pulley and a new chart than it is to reverse the A-B pulley on the machine. The main bearings feel ok, hope she can handle the high rpm's. What's a good main spindle oil to use? Thanks again for your help.
Reply:You don't need a tool to measure rpm. Mark the pulley and turn the motor one revolution and do some math.Would it be simpler to switch the pulley on the motor?Last edited by mikecwik; 03-20-2015 at 05:48 PM.
