Thread: Milling Machine problem - spindle slow to start

Caps of that size are pretty hard to test with any equipment at home (unless your Ray maybe) Older caps will leak oil if they go, but i don't know about new ones...
One thing you can do is disconnect the caps one at a time and try turning the machine on. If one of the caps being removed makes no difference it is probably at fault.

Originally Posted by whitey56

See if you can rotate the head 180 degree and use the weight of the motor to pop it, put in longer bolts so it can only drop 25mm or so. It took me about 3hours to get my motor off but it had been there for a lot of years.
I did not know these gearboxes had a neutral is it between High and Low i'll have a look for it

There will be no dedicated neutral but if you take it out of gear by moving either or both selectors the spindle will be free to rotate by hand or not rotate when the motor is started.

Originally Posted by variant22

Thanks for the notes on the capacitor Stuart. I decided to replace the gearbox oil and whist the head was tilted I was going to check the motor out, but it is proving tough to get off. I may not have responded directly, but the first thing I did (before tilting the head) was popped off the cover and had a look at caps. There are two (branded sok99.com). Interestingly there is one marked 240v, and one marked 415v. I am not sure how to check if they are OK. There was a smell of somewhat toxic plastic when I removed the cover. No idea what it was, but certainly not burnt. I checked out the switch box, and all looked (by eye) OK. Surprisingly the switches were branded as being made by Siemens!

With respect to the caps, what is my next step? Should I just purchase (source?) replacements or is it time to pull out the multimeter?

Is there no drain plug to drain the oil without rotating the head.

Originally Posted by pipeclay

Is there no drain plug to drain the oil without rotating the head.

As far as I "was" aware. I did a quick search and now saw there is a plug hidden under the head. My drain plug is covered with what looks like grey casting sand and yellow silicon(?) gunk. Interestingly when tilting the head oil leaks out of the filler plug. The plug was tight, so not sure what the deal is there. I have not inspected as yet to see what was up with it.

No real drama if the plug was tight.

Did you rotate the head past 180 for the oil to come out of the filler,if not I would say the head was over full.

Were you able to see the level on the sight glass before tilting the head,if you couldn't see a distinct line you may need to remove and clean the sight glass,there may be a line across your glass or dot,when you refill fill to either the line or dot or until the oil is halfway up the sight glass,I think the oil should be a 68 grade.

Originally Posted by pipeclay

No real drama if the plug was tight.

Did you rotate the head past 180 for the oil to come out of the filler,if not I would say the head was over full.

Were you able to see the level on the sight glass before tilting the head,if you couldn't see a distinct line you may need to remove and clean the sight glass,there may be a line across your glass or dot,when you refill fill to either the line or dot or until the oil is halfway up the sight glass,I think the oil should be a 68 grade.

I tilted the head to 90 degrees. It was running straight out of the filler plug. When looking at the glass it was 3/4 the way up. When I refill the oil I will fill it to half. I have some ISO 68 oil at the ready to go in. I figured I would hold the phone on filling it in case I need to rip the gearbox apart to inspect.

I have ordered some Ebay capacitor replacements. They cost half of nothing so figured I may as well. That said I expect to be waiting a month for them to arrive from Honkers. As far as removing one for in-situ testing, I am not entirely sure what I would do with the wiring that attaches them. Wrap it in electrical tape?

Tape or just a connector.
I won't tell you what i would do, it may be frowned upon and is not really very safe......

Originally Posted by Ueee

Tape or just a connector.
I won't tell you what i would do, it may be frowned upon and is not really very safe......

Probably same as me, leave them hanging in the breeze and hope they don't touch?

The fill plug on my 45 mill has small breathers in the side. If I tilt my mill to 90 deg some will slowly start to seep out.

Cheers,

Simon

Per Stuarts recommendation (thanks Stuart!) I replaced the motor start capacitor today. With the replacement capacitor the motor spun into life like never before. It spins up instantly. I cannot detect any lag at all, which is terrific!

I do however have an issue: The replacement capacitor is ~1.5cm larger than the capacitor it is replacing. Unfortunately it will not fit in the electrical box. The capacitor in question is: Buy Aluminium Capacitors Capacitor,electrolytic,aluminium,motor start,220/275Vac,150uF Kemet 150MS22ACMA1RSC online from RS for next day delivery.

Any ideas of a local source (with fast postage) for a 150uF 240v Motor start capacitor in a smaller package? I do not fancy butchering the nice plastic electrical box on the mill.

Take a look at the motor rewind places. They should have them on the shelf. Electrial wholesalers usually get daily deliveries from their suppliers. I'm sure they can get them in. Rural Irrigation pump specialists would be another place too look.
Maybe size is a benefit. A lot of people have been complaining of blown caps on new lathes and mills. They are probably under spec.

Can you clarify- you said you bought the caps on eBay, but the link you provided is to RS Components. Also, the specs of the cap you linked have a voltage rating of 220V. That's too low. I'd be hunting down a cap with a 275V rating ASAP. What is the voltage rating printed on the cap?

HI

The peak voltage of 240 AC is around 340 volts , 240 is the RMS value ( root mean square ).

Originally Posted by jack620

Can you clarify- you said you bought the caps on eBay, but the link you provided is to RS Components. Also, the specs of the cap you linked have a voltage rating of 220V. That's too low. I'd be hunting down a cap with a 275V rating ASAP. What is the voltage rating printed on the cap?

I purchased a capacitor from RS when I saw they did next day delivery. I figured the one I purchased on Ebay would be up to a month away. As for the 220v rating, the title states on the RS site that it is 220/275Vac. The marking on the capacitor states AC 220V 3MIN / 1.7%

To be honest, I thought it was 220-270v range as per the RS title for it. Looking at the capacitor I think I know how they (RS) got confused. The capacitor says 150uF +25%. I figure RS have applied this +25% to the 220v to get 275v, when it looks to be meant for the capacitance not the voltage. I am not really sure what is up with that. I guess now the question becomes can this 220v capacitor be utilized safely?

Originally Posted by variant22

I guess now the question becomes can this 220v capacitor be utilized safely?

I would say NO. This is from the Illinois Capacitor Inc website on Motor Run capacitors:

1. Strict attention should be given to determining the voltage rating of the capacitor, with specialweight being given to the type of operation: intermittent or continuous. In general, the voltageacross the capacitor will be higher than the supply voltage. For these reasons, it isrecommended that the rated voltage of the capacitor be at least 30% higher than the supplyvoltage to the motor. For higher reliability or if other adverse conditions exist, an even higherrating may be recommended.