Which type of single phase motors are best for constant use – power hacksaw

[ell81Participant @ell81]

I need a single phase motor for a power hacksaw, I want to use a single phase one – 3/4 hp.

Which type of single phase should I be looking for?

I just want to know the basics of types of single phase motors really. Thanks.

[Dave HalfordParticipant @davehalford22513]

You want one marked CONT or S1. Run all day and night.

Lots of tech info online

[peak4Participant @peak4]

Also, it might depend on what hacksaw, and whether there is a secondary shaft to lower the gearing.

A 4 pole 1400rpm motor might be too fast, so consider a 6 or 8 pole one, though they are often harder to find, and more expensive.
A 2 pole 2800 ex compressor motor will almost certainly be too fast.

Bill

[noel shelleyParticipant @noelshelley55608]

I would say foot mounted, 5/8″ shaft, 550W 220/240V, 4 pole 1420 rpm is what I used on an old Rapidor . A Brooks motor would be ideal. It then depends on how fussy you are about protection of the motor, in an ideal world you would use a direct on line ( DOL ) starter with overload protection, set to the motors full load current and properly wired for single phase. Plan B would be to use a NO VOLT release or self latching relay. Your saw may have a push button switch but it will not be a cut out and bearing in mind that if there is a power failure and you are working on the saw it may re start unexpectedly. As you may leave the saw unattended in operation the DOL will save the motor if an overload situation arises. Good Luck. Noel.

 

[Clive FosterParticipant @clivefoster55965]

Generally motors with two capacitors, one for start and one for run, are the considered the best type of general purpose single phase motor being up for virtually any suitable job. At a price.

Starting loads on a power hacksaw are low so simple capacitor start or induction start will be fine.

The type to avoid are the ones with a permanently connected starter winding, ie no centrifugal switch. These are intended for fan or similar use driving very specific load. The act as a sort of two phase motor and are usefully more efficient than a simple single phase motor at the specified load but have very limited ability to cope with different loads. Outside their sweet spot they rapidly get hot and melt the winding insulation.

Rule of thumb these days for new or not very old second hand motors is that if it has a capacitor it will be fine. Simple induction start motors seem to have fallen out of favour in recent years despite working just fine.

Speed range for power hacksaws in generally between 50 and 130 strokes per minute. 80 or a bit less is probably a good compromise for home shop use.

More than you ever wanted to know about blade speed here :-

https://diamondsaw.com/resources/power-hacksaw-use/

Compared to hand saws and bandsaws recommended power hacksaw blades seem very coarse pitch.

Clive

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