Thread: Woodfast Table Saw Info Request

As a rule of thumb if all else fails,

Run blades at about 80-85 of max speed branded on the blade. (If the brand has been worn off the existing blade look at similar construction/pattern blades in a store and note their max speed and use that.)

Measure diameter of arbour and motor pulleys. Arbour speed = motor speed x motor pulley dia/ arbour pulley dia.

Motor will either 1440 or 2850 RPM (standard speeds for 50Hz motors) +/- abt 20 RPM variation is slip allowance between brands/models.

If you looking for a motor from scratch, 2850 RPM 2 HP is a good starting point, higher power can be helpfull if you can supply the power to it, dedicated 15A power points etc.

Malb

Thanks for your response. I have followed your advice and sourced a 3HP, 2850 RPM single phase Chinese motor. Quite an interesting experience to get some information on the pole wiring to get it to run counter clockwise as the manufacture and I have a different place to stand when looking at the motor to decide which way is clockwise or not. We also had some language barriers to get through as they wanted to sell me another container load of motors.

I am now left with trying to get my pulley wheel machined out from 19mm to 24mm to match the new shaft or trying to source another double V belt pulley at 2 1/2". Anyone with a pointer on the best approach?

Peter

How big is the pulley on the arbour?

As a guess I think you are wanting around 4000RPM on the arbour, so you want to step up 1.3:1 to 1.4:1 on the drive to get the RPM. Check blade ratings and run at about 80-85% max speed as originally suggested.

If you have 2.5 inch at the motor then the arbour pulley would be below 2inch if you were going to get the blade speed. At that diameter, power transfer at the arbour pulley would not be great due to low contact area and the sharp curve in the belts.

You might be better to measure the arbour pulley diameter, and buy a motor pulley to suit providing the step up. I suspect that there may not be a lot of boss material left in a 2.5in (62mm) pulley after you bore the hole to 24mm, particularly if you need to install a key. If you go with boring the existing pullley, try putting a request in the metalwork section indicating where you are. You will probably get an offer within a day or so.

As an example, my old 1.5HP 2850RPM 10 inch saw runs a single A section with 5 inch motor pulley and 3.5inch arbour pulley for about 4300RPM at the blade.

The motor pulley has an inside diameter of 50mm (stamped Mosman 2 1/2"?) and the arbour pulley has an inside diameter of 65mm. In my calculation this seems to give me a speed reduction ratio of 0.77 but the saw must have worked correctly at one time but may have have had a much higher speed motor than the 2800 rpm motor I bought.

Following the outline provided I guess I'll shop around for a 90mm double belt pulley. Thanks again.

If it originally had an induction motor (no brushes), the standard speeds for 50Hz power are either 950, 1440, or 2850 RPM. This is nominally derived from the number of mains cycles per minute (50 per second x 60 seconds per minute =3000) divided by the number of winding pole pairs in the motor, with an allowance for 'slip'.
2 pole (1 pole pair) gives 3000RPM
4 pole (2 pole pairs) gives 1500RPM
6 pole (3 pole pairs) gives 1000RPM.

In order to produce torque and power, the motor runs slightly slower than the nominal speeds (typically about 5%) giving the speeds above. There is some variation in slip allowance between manufacturers and models, but nominal speeds are within about 2% of those quoted.

I suspect that the saw was originally supplied with a universal (brushed) motor rated at about 5000-6000RPM to cut efficiently. Would be rare in a 3HP version, but 1.5 to 2 HP are not uncommon, for example in 'portable' thicknessers. This style of motor has poor speed regulation, with speed being affected by changes in load or voltage.

Someone recently was discussing Delta saw with a universal motor.