Thread: 8'' bench grinder issue

I assume its 240v?
Does it have any capacitors?
If so check them first.
Although I have seen the odd grinder that needed a little help lol
Stuart

Does it quite happily spin backwards if you start it in that direction?


Probably the starting capacitor.

It is usually located under the main body of the machine. Turn it upside down and take the base off. The capacitor is the cylindrical (probably) thing with the wires running to it.

Take it to a sparky or an appliance repair shop if you don't want to replace it yourself.

My guess would also be the starting capacitor. I've heard of the exact same fault in other machines with an electric motor.

Hi

Jaycar sells motor start caps.

cheerio, mike

Agree it sounds like a start winding problem but be aware not all motors are capacitor start.

Some simply use a separate winding whose inductance is sufficiently different from the main winding to allow starting.

So make sure the centrifugal start winding cutout switch works (should be on when stopped and off when a few 100 rpm) and start winding is continuous - also that there is limited load on the motor at start

If the grinder is over 15 years old the contents of the capacitor may well be highly carcegenous.

When I took my GMF's failed capaitor into a shop they told me to take it away and ensure I washed my hands if I had touched the leak.

Apparently it contains PCB (whatever that is) but I do know from my job that it was used in old transformers for cooling and is a real problem for the electricity supply people as disposing of the transformers cost way more than when they were built.

Originally Posted by Avery

Does it quite happily spin backwards if you start it in that direction?


Probably the starting capacitor.

It is usually located under the main body of the machine. Turn it upside down and take the base off. The capacitor is the cylindrical (probably) thing with the wires running to it.

Take it to a sparky or an appliance repair shop if you don't want to replace it yourself.

You can spin it backward by hand but there is no machine setting or switch to make it run in reverse

Originally Posted by HavinaGo

Agree it sounds like a start winding problem but be aware not all motors are capacitor start.

Some simply use a separate winding whose inductance is sufficiently different from the main winding to allow starting.

So make sure the centrifugal start winding cutout switch works (should be on when stopped and off when a few 100 rpm) and start winding is continuous - also that there is limited load on the motor at start

i got a bit lost with the centrifugal start winding but i believe run capacitor is the alternative to cap. start. would that be correct?

Thanks for the replies everybody.
Just to be clear on this fact..i realize its only a bench grinder the thing is i seem to have a problem with letting things beat me lol
Anyway i took off the bottom plate to try to locate a starting capacitor & all that was in there was the switch housing...now saying that there were TWO wires taped up (obviously by a previous owner) the are both female connections & did not have any clear place for them to go.
So, next step was grinding wheels off & inspect inside the covers, things looked as the should to me...admittedly a novice, so pls see photos & if you can offer advice thatd be great. cheers

Hi mistercartoon,
I have just fixed my 1/2Hp. Motor on my Leda Lathe.
My Electrician Friend, pulled a 4ft. 2 x 20w Fluoro & the Cap. in it was big enough in power to make my Motor go properly for the 1st. time.
You maybe as lucky as I was. Certainly worth a try. Cost = Zilch.
Regards,
issatree.
PS; The only one I could get at Jaycar, was a sq. one & would not fit. Cost $15.

I am fairly sure that there should be a starting capacitor between those two wires.

You said that when you turn it on you have to give it a spin by hand to get it started and then it runs normally. If you give a spin in reverse, I think you will find that it will happily keep spinning that way.

The previous owner may have removed the starting capacitor in order to make it spin in reverse - that can be quite handy for some sharpening, buffing operations.

I think you need to get one of these

Motor Start Capacitors - 20uF - Jaycar Electronics

and connect it between those to wires.

Or better, find a friendly electrician or appliance repiar shop.

Originally Posted by Avery

I am fairly sure that there should be a starting capacitor between those two wires.

You said that when you turn it on you have to give it a spin by hand to get it started and then it runs normally. If you give a spin in reverse, I think you will find that it will happily keep spinning that way.

The previous owner may have removed the starting capacitor in order to make it spin in reverse - that can be quite handy for some sharpening, buffing operations.

I think you need to get one of these

Motor Start Capacitors - 20uF - Jaycar Electronics

and connect it between those to wires.

Gday there. i have afeeling u could be right on the money there. im no sparky but 2 female connection (that clearly should go onto male terminals) taped up i think would indicate that. Ill grab a cap start...thanks 4 the link & ill try it. hey..thats all you can do right?
Thanks again cheers

Hi all
just had a look in side one I have and yes the 2 white wires go to a starting capacitor.
100 mfd . had it for 30 years. still works ok......
Tony

Re the two caps mentioned herein

1 seems too small while the other seems too much

Take it to a motor rewind shop who will fit the correct size.....volts KILL if you get it wrong!