BANDSAW PULLEYS

4/6/04, 7:00 PM #1

Brad
Guest

BANDSAW PULLEYS

Brad

>I have an old 12" Craftsman bandsaw with a 1/2 HP, 1725 RPM motor. This motor does not have the power needed to thick, green wood. I have a 1.5 HP, 3450 RPM motor that I think will easily mount to the saw, providing needed power. I will need to change both pulleys to reduce speed from the motor to the wheel (I can't just increase the pulley on the wheel, it would be too big, hitting the bottom of the table). I remember seeing a formula somewhere to determine needed pulley sizes, but of course, I don't know where I saw it. Does anyone know where to find this formula, or what size pulleys to use? Thanks in advance.

Re: BANDSAW PULLEYS

4/6/04, 7:09 PM #2

David Eaves
Guest

Re: BANDSAW PULLEYS

David Eaves

>Hi there,

To scale the speeds all you need to do is measure the pulley diameters and take the ratios.

e.g. Pulley diameter 3" driving 6" diameter pulley on a 1000rpm motor

Speed = 3/6 x 1000 = 500rpm

Now say you want to keep 500 rpm but use a 2000rpm motor

Speed = Pulley Ratio x motor speed

500/2000 = Pulley Ratio = 1/4

So you would need pulleys that had a ratio of 1 to 4, say 2" driving 8"

Hope this helps, you should be able to do that calculation to work out your required ratio then look for pulleys that are suitable sizes.

David

Re: BANDSAW PULLEYS

4/7/04, 12:31 AM #3

John Trant (aka Boxes-n-Bowls)
Guest

Re: BANDSAW PULLEYS

John Trant (aka Boxes-n-Bowls)

>Dave is right but there is a different way to think about it. Since the new motor is going twice as fast as the old motor, you will need a motor pulley that is half the diameter as the old motor pulley in order to maintain the same speed (assuming you can use the same belt).

The proof:

The circumference of a pully is pi*diameter. Halving the diameter halves the distance around the pulley which will halve the length of belt that a single revolution will draw. Doulbling the motor speed will compensate for the larger pulley and thus result in the same rate of drive on the belt as before (and the same RPM on the bandsaw blade).

John

BANDSAW PULLEYS

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