Problem with a dremel

[ron vale 3Participant @ronvale3]

Type 4000 drill

Using a mandrel with the cylindrical sanding attachment( the ones that slide onto a rubber mandrel and you tighten them up)

Cleaning up Brass sheet with soft solder on it. suddenly revs drop from about 10k and starts to run very lumpy esp a low speed setting

Put it on high speed and runs ok. The 5k setting is more like 500 and very erratic

Could it have ingested some of the very fine brass and solder that has been removed?

And if it can be clean at home any suggestions

TIA

[ron vale 3Participant @ronvale3]

Erratic running

[DiogenesIIParticipant @diogenesii]

Hm, maybe. ..I'd (unplug!) and check the brushes first, they are under the little caps on the sides opposite the speed switch – the original brushes aren't very generous..

If the brushes are okay, whilst they are out, peer down the little hole and see whether there's debris stuck between the segments of the commutator which is probably the most likley place for trouble of the kind you describe.

If you can see debris in the commutator slots, use a cocktail stick or a splint of wood to fiddle it out of the brush hole, or dislodge and shake it out of the back cooling slots.

If you need to 'split' it, the screws are some squitty Torx size (sorry, they're not in mine anymore – could be T2.5?), it's straightforward inside, note how the cable is routed between the pillars ('cos you'll have to get it back exactly the the same way if it falls out).. ..the motor is supported (I think) in a rubber bush at the end, and might have a 'hole and pin' register to stop the bearing spinning that has to be lined up on reassembly.

The bearings are supported by the plastic casings which aren't very accurately moulded, I had to fiddle around with the screw tension (to the point of tiresomeness) once I'd reassembled mine in order to get it to run smoothly at high speed..

[An OtherParticipant @another21905]

Diogenesll has the answer. My Dremel was also erratic, and I suspected at first that the power lead had broken somewhere, but it eventually turned out to be the brushes. They had worn over time, and were making erratic contact with the commutator.

I couldn't locate any new brushes where I lived, and eventually made some new brushes myself, cut down from some spare motor brushes I had. Diogenes is also right about the poor fit of the brushes in the casing – I had a lot of difficulty getting them to fit and slide smoothly. I had quite a bit of difficulty making the new brushes parallel-sided, so they would slide easily. And as Diogenes says, take careful note of how things fit together – I nearly 'binned' the thing because of this.

I thought about making the brushes a little longer, so they would last longer, but there was very little space to do this. Since then I have bought a couple of spare brush sets for later use.

[noel shelleyParticipant @noelshelley55608]

Hi Ron, Small air cooled tools esspecially 240v ones used for removing metal in fine particles can be quite dangerous as the metal can form a track that will cause a short circuit – this will destroy the electrics. Regular blowing out with compressed air will help. As others have said the brushes may be the cause and if new brushes are not available then they can be made from the brushes of an old 12v car dynamo eg Lucas. Noel.

[Andrew TinsleyParticipant @andrewtinsley63637]

Last time I looked for 12 v car dynamo brushes, there were none to be had anywhere. Please tell me where you get them from!

Andrew.

[John HaineParticipant @johnhaine32865]

As he says, old dynamos!

All this will be detracting from the built-in obsolescence of Dremel tools…

[V8EngParticipant @v8eng]

Posted by Andrew Tinsley on 02/05/2021 13:34:54:

Last time I looked for 12 v car dynamo brushes, there were none to be had anywhere. Please tell me where you get them from!

Andrew.

Could try here, worth asking as they even offer to make obsolete brushes:-

Carbon brushes

 

 

Edited By V8Eng on 02/05/2021 16:23:33

Edited By V8Eng on 02/05/2021 16:26:53

[Andrew TinsleyParticipant @andrewtinsley63637]

It now seems that you can get the dynamo brushes with no problem. When iIchecked a few years back, could not find any!

Andrew.

[noel shelleyParticipant @noelshelley55608]

ANYTHING old, car, truck boat Etc ! HC cargo, an offshoot of BOSCH. Brushes for a 50+ year old American alternator, on the shelf !!!! Their catalogue is 10" thick in several volumes, it's an encyclopaedia of parts !!! If you have trouble dealing with them PM me. Noel!

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, you can always go to Dremel click on Service & Support, scroll down to spare parts and enter your model number, and select your country/voltage, seems to be under brush-spring set.

Regards Nick.

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