DP speed formula?

[Robert Galloway]

Because within a reasonable range of applied voltage, the speed is determined by the applied frequency. 60 cps in the US.

bob g.

GTO69RA4 wrote:

[Robert Galloway]

How to calculate pulley/rpm problems is pretty trivial and has been beat to death. What's the most practical way to get yourself a low speed/variable speed drill press at minimum effort and expense? Anybody got a prime example lying around?

bob g.

Charles T. Garrett wrote:

[Robert Galloway]

The ratios are exactly as he has stated. Common sense dictates that a smaller drive pulley to a larger driven pulley gives a speed reduction. Little pulley on the motor, larger pulley on the spindle. Slows down. How much? The ration of the pulleys. 1 /58 to 6, 2 to 3, whatever it might be times the motor speed gives the spindle speed. If the motor pulley is larger then the spindle pulley then the whole things reversed and the spindle speed will be greater than the motor speed. Use logic and don't get bogged down in the "rules" of how to calculate this.

bob g.

the need for a web site calculator to calculate the ratio of two pulleys if gross overkill. Everybody here has at least the microsoft calculator with w>

[Ecnerwal]

Same way you get that for that on a lathe. Pick up a treadmill VS DC motor for free at the recycling barn, or for cheap by paying a surplus outfit or buying the used treadmill in the classified ads. Yank motor and controller, slap into drill press, vary torque by belt setting and speed by control knob.

[Morris Dovey]

[Repost - Qwest ate original response]

Alex...

I haven't seen a formula - but I probably missed some of the responses, too. It looks to me like one formula might be:

motor RPM x drive pully diam = spindle RPM x spindle pulley diam

You'll need to measure your drive pulley before you can do the calculation.

[Guess who]

I missed the original posting. However you are right. The OP needs to measuer pully size [diameter]. The ratio of speeds is the ratio of the diameters. I think of two wheels, one 1 unit, the other 2 in diameter. As the belt moves around the larger, which turns once, that same distance is covered by the smaller which must turn twice, and vice versa. To slow down, the larger must be on the spindle, the smaller on the motor.

I don't know the drill setup, but most these days are fixed sets. If there is room to change pulleys, just divide 1700 by 200 to get 8.5, and the front pulley must be that much bigger than the rear.