Thread: Arcs in an electric drill

G'day Kevin,
It sounds like the brushes may need attention........probably replacement.

Kevin,

The drill and most hand held tools use a "universal motor" which means that it contains carbon brushes to get current to the armature (rotating motor shaft) windings.

All universal motors characteristically produce sparks between the brushes and the commutator (the part on the shaft that the brushes make contact with) whenever they are running. The other common electric motor type is the induction motor, where the current in the armature is magnetically induced so there is no need for brushes, and hence no sparks during normal running.

From your basic description in the initial post I suspect that the unit is operating correctly and that the arcing was more obvious than normal because you were operating in significantly darker surroundings than you normally do.

However, that said, if the drill has done a fair amount of work in its 15 years, it is possible for the brushes to be worn, and hence making an intermittent contact with the armature. This would increase the amount of arcing, but should also reduce the available power and speed of the drill.

Manufacturers used to supply one set replacement brushes with tools, and some still do, so you might have the set stored away. If not, the normally are readily avaiable and fairly cheap. If you suspect the brushes, I would advise having them changed asap. Continued use with worn brushes will cause damage that is expensive to repair.

A fault in the windings on the armature could cause an increase in the amount of arcing, but would normally be accompanied by some overheating and burnt enamel smell, and the tool would occasionally not start when triggered, but start happily if the chuck was rotated a small amount and retried.

I think there is probably no problem with the unit at present. But if you are concerned, you might try and have the unit checked by a qualified service person. However the cost of a basic check/service could get close to the cost of a new handyman class drill.

Malb,

Thanks for your reply; I must say that your explanation makes it clear as to what I should do.

My knowledge of electricity is limited to less than what I learned in high school so your information enlightened me.

I shall ring the local Ryobi service people on Monday and ask them the price of having the drill tested and the brushes replaced. If - as you suggest it might - the cost of such servicing approaches the cost of buying a new one then I shall buy a new drill, which leads me now to pose another question: are the suspiciously cheap GMC drills that you see advertised any good? I mean do they pack up and die soon after purchase or do they go on and give reasonable service?

Perhaps a better question to ask is: ' do tradespeople buy GMC drills?"

Thanks for your responce and clear answer Malb,

Regards,

Kevin.

I don't know what the nice man would charge you to change the brushes in your drill, but it is a very easy task to do yourself. Then the total cost would be the cost of the brushes, which would certainly be less than the cost of a new drill.

Kevin, The point that I was trying to make was that the arcing is always present, but would be more obvious than normal because of the dark environment. You suggested that the unit worked normally, which probably indicates that it OK. As a test drill a few holes under normal (in your experience with the drill) work and light conditions.

If everything seems normal then, I would not even bother considering servicing or updating. If it gets a bit warm, arcs more than you have experienced in the past, or gives of a burnt enamel smell, that is the time to consider service or replacement.

Any pro service people have to be charging minimum $45 per hour plus parts to maintain a workshop and pay wages and overheads. Dropping it in for a checkup to find there's nothing wrong can easily run up close to half the cost of replacing it.

If you can keep it running, it will probably be a better tool than a 'similar' new one due to all the home level tools coming out of China these days.

Malb, thanks for that advice.

Yes, my drill is functioning powerfully and normally. There's no change: neither to the sound nor the smell nor the way it starts. After reading what you have said I'm going to leave it as it is unless something changes.

It's a good piece of equipment with lots of grunt and I want to keep it.

Again, thanks Malb and best wishes.

Regards,

Kevin

Originally Posted by malb

But if you are concerned, you might try and have the unit checked by a qualified service person. However the cost of a basic check/service could get close to the cost of a new handyman class drill.

One word of caution on that, if you take it in for a look at they'll probably sting you $20 and upwards to look at it by a service bloke. I did that once, got a Metabo sander checked out and wasn't told of a look at fee, $20 they wanted just to tell me several days later that I could fix it, but the bushes and labour would cost more than buying a new model.

I told them to shove it and keep the sander, no way I was going to pay $20 for something that couldn't be fixed.

Being of the electrical/electronic persuasion, I normally don't take things anywhere to be checked/fixed. However I am aware that it is common practice for service facilities to charge to provide a quote for repairs, on the basis that the quoting fee is only applicable if the customer decides not to accept the quote.

For a tool or TV, video, DVD, computer, household appliance etc, it can take half an hour or more to open a unit, examinine/test relevant parts etc, locate and price spares if required. At the end of the day, someone has to pay for this time or the business goes down. By the end of the quote preperation, the customer gets to know the actual cost to repair the unit properly and can make an informed decision as to viability etc.

To all intents, the difficult job (diagnosing problem and locating/costing parts) is done. If the customer gives the go ahead, the parts are purchased and installed, the unit reassembled and tested, and the unit is restored to a safe working condition.

Most reputable repairers will advise when you drop a unit in if the think its uneconomical to repair due to parts availability and cost, labour etc.

Originally Posted by adeben

I don't know what the nice man would charge you to change the brushes in your drill, but it is a very easy task to do yourself. Then the total cost would be the cost of the brushes, which would certainly be less than the cost of a new drill.

Thanks for your reply: I'm going to leave it for now but I'll keep your advice in mind for future use.

Regards,

Kevin

Originally Posted by Waldo

One word of caution on that, if you take it in for a look at they'll probably sting you $20 and upwards to look at it by a service bloke. I did that once, got a Metabo sander checked out and wasn't told of a look at fee, $20 they wanted just to tell me several days later that I could fix it, but the bushes and labour would cost more than buying a new model.

I told them to shove it and keep the sander, no way I was going to pay $20 for something that couldn't be fixed.

Thanks for your reply Waldo.

Regards,
Kevin

I agree that if your drill works OK don't touch it.
However in defense of the honest power tool repair people, I must say that as an aficionado e-bay and cash converter buyer, I land second hand power tools all the time.
I only buy best brands in good nick but when I have the tool I take it straight to my trusted repairer who knows exactly what I want him to do. Pull apart, change bearings and brushes, polsih collector, general clean an grease, change any obvious broken or spoiled parts, test switches... and voila!
I have a new tool for less than half price most of the time.
To give you an idea, a drill that needs bushes and bearings grease and nothing else will probably cost between $40 and $50. Money well spent.
Could I do it myself? Yes...but my time costs more that what Mr Mac the friendly repairman charges me so I let him do it, plus he can get spare parts with one phone call delivered. I don't.

Hi Marc and thanks for your reply.

Your servicing of electric tools is interesting.

I'm after a couple of power tools or at least I will be in early 2009.

Such machines when new cost drug money so I'll investigate our local Cash Converters over the next few months. If the servicing you've outlined is as cheap here then buying secondhand is quite the go.

Interesting.

Thanks again Marc,

Kevin.

Cashconvertors is one place to go. Others are weekend markets, auctions and e-bay.
Stay clear of the cheaper brands, they are usually throw away and not worth your time. Stick to the reputable dearer brands, take down the model number and ring your local tool shop for a new price. You will also find out if it is discontinued model or still current.
Half the new price should be your limit, less if it is obsolete model.
Sometimes you may take a gamble on something that seems doomed, but it is a gamble. I paid $50 for a Bosh "brute braker" jackhammer, worth over $2500 new. Armature was burned and some bits an pieces mising. My repairman took a few month to put it all togeather, the bill was $600. Sitll sitting in my shed waiting for a coat of paint. Could probably get $1500 for it if I wanted. I wonder if I'll ever use it.