motor brushes ?

anyone know where to buy or recycle carbon materiel to make small power tool brushes ?

I restore old powertools and i'm paying £6 for a tiny pair, and i know the materiel is just pennies. would the carbon rods from d cell batteries be the right materiel ?

You will find carbon rods from zinc carbon batteries are unsuitable on the whole..too abrasive.

brushes are MOSTLY graphite with binders to control:- resitance, and trade off between wear rate and wear of comutator....

Even large brushes form say a low voltage motor might be unsuitable to cutdown for a mains motor..

I have used pure graphite (artist ) to make emergany brushes and the results less than ideal..very high wear rate of brush, filfthy motor and VERY high inrush current ( little or no resistance from brush)..

Sorry no easy answer but slight adaption of simular "rate" brush more readily available ( or cheaper) might be posible ..

Hi

I'd suggest a search on EBay for brushes might be a better bet, from memory the carbon rods in batteries will be too hard and probably "gritty" (coarse) for your use. On EBay you will find generic brushes from China being offered by physical size, often in boxes of 10 pairs for a fraction of what you'll pay for a single pair from a tool spares supplier - if you can find one and if they can supply them. Recently I wanted brushes for a Ryobi sliding miter saw. The "official" brushes came from the Ryobi spares warehouse in Germany at about £10 a pair. The unofficail ones came from China for about £5 for a pack of 10 pairs - from memory post free! Interestingly the "official" brushes appeared to be Chinese made as well. Both sets of brushes included the springs.

If you can't get the actual size you want get the nearest size above and a few minites (dirty) work with some fine glass paper will soon ahev them to a size to fit your brush holders.

I've also seen in a Google search a comapny in the UK offering brushes made to size - no idea of prices though - but I can guess!

Keith

Cant help with a source for you brushes but I will relate one of my own experiences with Carbon Brushes:

When I got re-married many years ago funds were tight what with the new nipper and all and when the time came to replace the Washing machine carbon brushes the £10 at the time was unafordable so off to the local motor factors and bought some Dynamo brushes of around the right dimensions for a Triumph Herald if I remember correctly, so suitably filed to shape in they went and all worked well for a while then about six months later they wore out again so same routine file to shape in they go...after around 18 months and the third set the motor armature was so badly worn it wouldnt take another set.

Popular concensus was that as the Triumph Herald brushes were a lot softer than the washing machine ones so they presented a constantly fresh "abrasive edge" to the copper armature wearing it out prematurely.

Apologies for the long tale

Paul

Hi Richard.
I agree that brushes from a mains motor will probably be unsuitable for a low voltage motor. (And vice versa.) Low voltage motors will need brushes with lower resistance to keep the voltage drop low. I suspect that copper powder is added to the graphite to achieve this. I suspect that the brushes that Paul used on a mains motor could have had a shorter life possibly due to the current flowing between segments of the commutator at the point when the brush bridged two segments of the commutator. With brushes with a higher resistance this current would have been less. Also the dust from the brushes collecting between the commutator segments would provide a lower resistance path between segments. These comments are just theories. I have not seen these suggestions elsewhere.

Les.

Just a comment from my apprenticeship days if you want to reduce carbon brushes in size use GLASS paper NOT emery particles of emery will embed in the carbon causing extra wear

Roy

Hi Richard,

I made replacement brushes an old battery carbon rod. These wher for an old power saw for nwhich brushes are no longer available. These home made brushes seemed to work fine.

Peter.

Once made a set of replacement brushes for a 100v dc motor by cutting down the brushes from a car starter motor. They had a 'coppery' tinge o the colour, so I suspect they were loaded with copper powder(?). Worked fine, without undue wear or dirt. I don't know if this would work for a 230v ac motor in a machine tool - the starter motor brushes were rated at nominal 12v DC, and of course at very high current (can be over 300 amperes instantaneously for a starter motor), so they must be fairly robust, and probably very low resistance, so may be worth a try.

Connections to carbon brushes is not always easy - I drilled a small (~3/16 inch) hole in the brush, and used a tightly fitting spring 'screwed into the hole, and a wire soldered to the other end of the spring.

Hi, I once made a couple of brushes from carbon rods out of a dry cell (battery) for an old style metal case Black & Decker two speed drill, they did work OK but there were a lot of sparks racing around the cumutator and they didn't last any amount of the time that genuine replacments did. I remember that at the time I counld not get any for a week or more, (how times have changed with the internet shopping) but I needed the drill before then to do some job or other in the house.

Regards Nick.

From my experience in 25 years in electrical maintenance. I have made small brushes from lager ones

I always used a file as emery paper dose leave particals in the carbon, there are different types of brushes some are plain carbon / carbon graphite / carbon graphite copper mixes if you use the wrong type you will get commutator ware Plain carbon are the most abrasive and the graphite type are the less abrasive. If you look at the original brushies you can get a good idea what type you need.

John

You can sometimes use the old dogde of putting a little piece of something on top of the old brush, between the brush and spring. Increases the spring tension and pushes the remaining carbon against the commutator.

A piece torn from a matchbox and folded up was the traditional roadside fix on DC motorcycle generators etc.

There are about as many grades of carbon brushes as there are motors to fit them to. One of my (old) books "Practial Design of Small Motors and Transformers" Edited by E. Molloy, 6th ed 1947 quotes 23 different grades, it depends on voltage, AC or DC, high or low voltage, and motor speed. It also depends on whether the mica is flush, or recessed. Back then a high speed motor was 10,000rpm, I'm sure its a bit higher on todays tools. Ian S C