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Determining Pulley Speeds

Determining the spindle speeds using a 4 step pulley on a drill press

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Comments (7)

What speed do I have here?

Can you tell me how to determine the spindle speeds I will get by using a 4-step pulley on my drill press? - Dale Potts, Athens, Ohio

We sure can, Dale. However, to do this we will need to know a couple of things more than just the number of pulley steps. We also need to know the motor speed and the outside diameter or diameters of the drive or motor pulley. Also, 4-step pulleys are most often used in combination with a second 4-step pulley. Here's an example of the calculations, based on a motor speed of 1725 rpm, with the motor pulley and the spindle pulley having equal step diameters but inverted placement (see drawing below). We will assume the 4-step pulleys have step diameters of 2", 3", 4", and 5". Follow these steps to find the approximate spindle speeds:

1. Divide the diameter of the driving (or motor) pulley step by the corresponding step size of the pulley mounted on the drill press spindle:
2 � 5 = 0.4
3 � 4 = 0.75
4 � 3 = 1.33
5 � 2 = 2.5

2. Then, multiply the motor speed by the results of the above calculation to get the approximate spindle speed at each pulley step:
1725 x 0.4 = 690 rpm
1725 x 0.75 = 1293.75 rpm
1725 x 1.33 = 2294.25 rpm
1725 x 2.5 = 4312.5 rpm

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Comments (7)

ZekFussel wrote:

Multiply the motor speed by the pully diamter(driving) & divide by the diameter of the driven pully. Works for laths, drill press's & a multitude of applications. 2"(driving pully) X 1725 (motor speeed) = 3450rpm now divide by 5" (driven pully) will get 690 rpm.

1/4/2012 03:19:45 PM Report Abuse

whelan353 wrote:

I read the chart on the inside of the belt cover.

7/5/2011 08:19:55 AM Report Abuse

hubcap52 wrote:

I have a 3 pulley machine too. Do I just repeat the process again for the 3rd pulley?

6/30/2011 06:28:09 PM Report Abuse

bernierdon wrote:

My drill press has the speeds right on the front. Noo calculations required.

6/30/2011 02:11:18 PM Report Abuse

knotcutter wrote:

i have a bench top with 3 pullys does this still hold the same for it.