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mantrid
01-03-2010, 03:57 PM
Off topic but I couldnt find a suitable forum and Im sure some of you guys use this type of tool.

My dremel 400 has recently stopped working properly. It buzzes but doesnt turn. It often starts when I spin the shaft with my fingers but it lacks power and the brushes spark exessively. It speed vary randomly and will often stop. While it is spinning it heats up exessively and starts smoking so I switch it off at this point. The brushes are about 7mm (minimum before change 3.2mm) and the bearings are ok and the shaft turns freely. Does anyone know what could be wrong with it?

Jammer
01-03-2010, 04:16 PM
On mine the rubber coupling between the motor and the head was stripped out. It's a piece of rubber tube that takes the shock of starting to cut. I don't know about the brushes sparking, they always do a little. Mine smoked too, from the friction inside the tube. I replaced it with a short piece of insulation off some 10/3 SO electrical cord. Fit perfect but you can probably get a new coupling from Dremal.

DarkArtiste
01-03-2010, 04:26 PM
sparking would indicate your brushes aren't contacting like they should, are they worn unevenly or chipped? do they slide freely? are the springs pressing them firmly against the commutator?

If the tool spins freely, then the bearings probably aren't suspect and if the brushes are doing their job, then it could be a simple case of deteriorated windings

mantrid
01-03-2010, 04:38 PM
sparking would indicate your brushes aren't contacting like they should, are they worn unevenly or chipped? do they slide freely? are the springs pressing them firmly against the commutator?

If the tool spins freely, then the bearings probably aren't suspect and if the brushes are doing their job, then it could be a simple case of deteriorated windings

Yes I suspected the brushes not contacting properly because of the sparks, despite them being over the min thickness. They are not chipped or worn uneavenly. The spring appears to be pressing against them.

What are the windings, and how can you tell if they are worn?

Why is it heating up to the poin it starts smoking. does this indicate a fault with the motor or is it something that normally happens but the turning shaft with fan would normally be cooling it down?

Bob S
01-03-2010, 04:41 PM
I don't have a Dremal by brand name but do have several other brands of die grinders and as Jammer said the flex coupling is probably the cause. On mine they used a piece of 3/4"Delrin round stock with slots cut in the ends for the shafts with roll pins to fit into. These slots become elongated by the roll pins until they make a full circle inside the coupling allowing the motors shaft to spin in the coupling and no longer drive the output shaft. I have taken to making up several replacements couplings ahead of time for mine since it is bound to happen over time especially when under heavy cutting pressure.

You need to determine if the smell is electrical or not but if the motor is spinning but not the output shaft or the output shaft can be held from spinning with motor still running then I would stay with the coupling as the first item to check. Also check for free spinning of the shaft and motor assembly you could have a failing bearing causing the overheating, the second cause for my die grinders going off line. I also have replacement bearings on hand also. Easy to find and get on ebay :? Bob

Heimo
01-03-2010, 04:46 PM
Off topic but I couldnt find a suitable forum and Im sure some of you guys use this type of tool.

My dremel 400 has recently stopped working properly. It buzzes but doesnt turn. It often starts when I spin the shaft with my fingers but it lacks power and the brushes spark exessively. It speed vary randomly and will often stop. While it is spinning it heats up exessively and starts smoking so I switch it off at this point. The brushes are about 7mm (minimum before change 3.2mm) and the bearings are ok and the shaft turns freely. Does anyone know what could be wrong with it?

my old blower had exactly the same symptoms I have found that there was a short circuit on the armature and it burned a winding or two it took VERY careful inspection of the armature to notice this (it was not very easy too see it ) and it was imposable to fix cause it looked like the manufacturer dipped the armature in some kind of epoxy I could not even get the windings off
the there are two possable cures

a find a new armature
b rewind the armature if possible

and option c not really a cure but if all else fails buy a new one

based on my experience I would say that the armature is shot

the windings are the coils of copper wire on the armature

mantrid
01-03-2010, 04:49 PM
I don't have a Dremal by brand name but do have several other brands of die grinders and as Jammer said the flex coupling is probably the cause. On mine they used a piece of 3/4"Delrin round stock with slots cut in the ends for the shafts with roll pins to fit into. These slots become elongated by the roll pins until they make a full circle inside the coupling allowing the motors shaft to spin in the coupling and no longer drive the output shaft. I have taken to making up several replacements couplings ahead of time for mine since it is bound to happen over time especially when under heavy cutting pressure.

You need to determine if the smell is electrical or not but if the motor is spinning but not the output shaft or the output shaft can be held from spinning with motor still running then I would stay with the coupling as the first item to check. :? Bob

Ive taken it apart and there is nothing like you describe. The shaft has a bearing at each end that locks into the casing when it is screwed closed. the bearing is also prevented from moving in the case by a rubber sleeve between it and the case. The rubber is intact and unaffected

Sylar
01-03-2010, 10:10 PM
Then your motor is most likely burning out.
The extra drawn current will create extra sparks at the brushes and will overheat the motor aswell.
Everytime you observe smoke another part of the windings loses the coating on the copper that keeps the winding from becoming a short cirquit copper block.

Not much you can do to stop this.
Should the fault in the winding be clearly visible and you are an avid tinkerer in electronics it might be repaired. It will never be the same though.
It's also possible to completely replace the windings, but this is hardly ever done on motors under 15 KW and even then it's only cost efficiŽnt with special or expensive motors.

Heimo
01-03-2010, 10:19 PM
Then your motor is most likely burning out.
The extra drawn current will create extra sparks at the brushes and will overheat the motor as well.
Everytime you observe smoke another part of the windings loses the coating on the copper that keeps the winding from becoming a short cirquit copper block.

Not much you can do to stop this.
Should the fault in the winding be clearly visible and you are an avid tinkerer in electronics it might be repaired. It will never be the same though.
It's also possible to completely replace the windings, but this is hardly ever done on motors under 15 KW and even then it's only cost efficient with special or expensive motors.

that is why I said he should try to find a replacement armature cause my old blower quit exactly the same way and it was the armature that was the problem but maybe it would be cheaper just to replace the Dremel

this is funny my dad actually had the motor to his band saw rewound the other dad it cost him the equivalent of $100 so yea it is expensive to get motors rewound

welder19
01-03-2010, 11:56 PM
I use a spray cleaner (aerosol) on all my elec tools and motors, spray it while the motor is running and it will clean out all of the dust and gunk from the brushes and such, most of the time the motor will pick up rpms as your spraying it and all the black stuff will run out, do this every so often and it will extend the life of your motor, keep the rpms and performance up and help them run cooler.

There are a few company's that make it, the stuff I have right now if CRC I think.

DO NOT do tihs with any other cleaners or solvents than the stuff that is specifically designed for cleaning electric motors, if you were to do it with carb cleaner or brake cleaner or such it will blow your face off with a big fire ball.

I normally get mine from Napa but I would think most decent size automotive parts stores will carry it.

Also make sure the brushes are sliding smoothely and are makeing good contact, sometimes dirt can get in there and bind or hang them up.

I normally fix most of my elec tools or have them repaired if it is beyond my abilities since I always buy high end top quality tools but as far as any Dremels go the only thing I have ever done besides clean them is replace the brushes, beyond that they are normally not worth messing with them ans just replace it.

welder19

Bob S
01-04-2010, 12:08 AM
that is why I said he should try to find a replacement armature cause my old blower quit exactly the same way and it was the armature that was the problem but maybe it would be cheaper just to replace the Dremel

this is funny my dad actually had the motor to his band saw rewound the other dad it cost him the equivalent of $100 so yea it is expensive to get motors rewound

If you do need to replace the Dremel try and stay with the same make and model. I learned this the hard way starting out by buying different makes. I now buy only this same Makita model of die grinders, not that they are the best but because if one goes out the parts will interchange with the others I have as well as the replacement bearings, brushes and flex joints are all the same and purchasing the replacements or making them in quantity is made easier. Bob


http://i122.photobucket.com/albums/o268/castaway43/allpictures247.jpg

Lambda_drive
01-04-2010, 12:40 AM
I like dremels, they work very nice but they can be pricey. The good thing though is that Dremel isn't the only company that makes Rotary tools. Black & Decker has a rotary tool called, the Black & Decker RTX (http://www.target.com/Decker-3-Speed-Rotary-Spring-Clamps/dp/B0001GUDRI/). It's pretty much the same thing as a Dremel 400, but a LOT cheaper.

SPECS: DREMEL 400

2 amp motor
Speed Variable (5,000 to 35,000 RPM)
price: $90-$100

http://i.ehow.com/images/GlobalPhoto/Articles/5062753/182689-main_Full.jpg


SPECS: BLACK & DECKER RTX

2 amp motor
3 speeds (12,000/24,000/30,000 rpm)
price: $29

http://www.blackanddecker.com/ProductImages/PC_Graphics/PHOTOS/BDK/POWER_TOOLS/TOOLS/LARGE/GENERIC/RTX%25_1.jpg


The black & decker rotary tool is a pretty nice rotary tool, it can do everything a Dremel 400 can do and for $29 it's a steal. 8)
I don't know if the Dremel accessories will work on the RTX though.

One thing I noticed about mine is that it has more than 3 speeds, The speed dial has three settings, low, medium, and high, but you can move the dial between two settings and get different speeds.

mantrid
01-04-2010, 01:11 AM
The burning seems to be coming from the windings. There are two sets of wound wire. I dont know the terminology but there is one set around the shaft that rotates and another set around a non rotating sleeve that surrounds it and I think would be an electromagnet. I noticed a small black patch on the resin that surrounds the windings on the shaft. So think this might be where there is a problem. I suspect its knackered and I dont think Ill waste money getting brushes (£7 is quite expensive for two tiny pieces of carbon, they dont even have springs on them). I am very disapointed with this tool it was quite expensive for what it is and I would have expected it to last longer than 15months of occasional use. I think I will bin it and try a different make. That black and decker is cheap so wont be so bad if it packs up.

DarkArtiste
01-04-2010, 01:39 AM
if I'm not mistaken the shaft that spins is the rotor and the surrounding part is the stator.

nudge
01-04-2010, 02:39 AM
15months of occasional use
And I bet it only had a 12 month warranty :x

greencheapsk8
01-04-2010, 08:17 AM
hmmm my Dremmel better last longer than that :evil:
its a 320 series or something
man the bits are expensive though! like $15NZD for a milling bit :shock:

cxevalo
01-04-2010, 08:59 AM
http://i46.photobucket.com/albums/f121/cxevalo/103_0032.jpg

ten year old , or there about, dremel 395 with broken coupler.

Sylar
01-04-2010, 10:05 AM
I hate those type of appliances that break a few months after the warranty runs out, like they installed a timer in it or something.

My sister in law has a good trick for warranties that have expired.
Buy an identical product in the same store. Return the old product under the new warranty to get a new one.

You now have 2 new products, or at least one new and one repaired. If the store has a return policy you can even return one of them for cash or a coupon.

mantrid
01-04-2010, 10:35 AM
15months of occasional use
And I bet it only had a 12 month warranty :x

Yes
And I the cynical side of me sometimes wonder if they are designed that way. Then I think but would they do that as it would damage their reputation in the long run. Unless of course they (manufacturers) are all doing it and if they were designed with better components then they would last our lifetimes.

mantrid
01-04-2010, 10:40 AM
I hate those type of appliances that break a few months after the warranty runs out, like they installed a timer in it or something.

My sister in law has a good trick for warranties that have expired.
Buy an identical product in the same store. Return the old product under the new warranty to get a new one.

You now have 2 new products, or at least one new and one repaired. If the store has a return policy you can even return one of them for cash or a coupon.

Thats a good idea. I may consider this. The manufacturer benefits by making two sales (unless i get a refund on the one I take back) and I benefit by having two working tools.

Sylar
01-04-2010, 10:53 AM
If you don't get cash in return, the coupon can be used to buy dremel bits :-)

I think the only one who loses money from this deal is the manufacturer.
It's the store that sells 2 items and reaps the profit, and you get an extended warranty.

ragingslab
01-04-2010, 11:51 AM
I would have expected it to last longer than 15months of occasional use
Probably made in USA. :roll:

The Dremel may have better bearings. Most Black and Decker stuff is made for the home-handyman rather than for professional use, IMO. Cheaper, but won't handle abuse. I've ruined my share of Dremel's and also a Roto-Zip. My problem is cutting/grinding things either too aggressively or using on materials and thicknesses that it was not designed for. As I'm bogging down the motor, repeatedly, I tell myself "I am ruining this tool", then I continue to cut and grind in the same manner until the tool is useless.

mantrid
01-04-2010, 12:17 PM
Ive been looking at some air die grinders on ebay that has 3mm (1/8") and 6mm (1/4") collets so I could still use the dremmel burrs and stones with it. Anyone has experience of air versus electric. Are they long lasting? could they deal with agressive grinding of bronze? Any brands to recommend
Thanks everyone for your advice.

Bob S
01-04-2010, 03:02 PM
My sister in law has a good trick for warranties that have expired.
Buy an identical product in the same store. Return the old product under the new warranty to get a new one.

You now have 2 new products, or at least one new and one repaired. If the store has a return policy you can even return one of them for cash or a coupon.

Might be the reason they end up costing so much. :lol:


Anyone has experience of air versus electric.

I tried air as well as flex shafts with more powerful motors. The air grinders need lots of air if you have one with any power. The small ones are easy to handle but stall easily at the slightest cutting pressure .

The flex shafts usually have slower RPMs but have lots of power to cut. However, the shaft itself reduces easy movement and can tire out your wrist when working for long periods.

Having been doing this for several years I have finally settled on these 1/4" drive Makitas, they're light, durable and have enough power to drive a good sized carbide cutter without heating up. In fact, of all these grinders none have ever burn out the windings. I do go through brushes, couplers, and bearings. Makitas come with single sided shielded bearings that over time get fine material in them placing a drag on the motor. I then replace them with double faced sealed bearings and ended that problem. 8)

Initially I had problems with their switches but have gone to foot operated switches which makes for easier and quicker set down and pick up of another grinder with a different cutter. :wink: Bob

mantrid
01-04-2010, 04:28 PM
I have this model compressor

http://www.mynewcheap.co.uk/products/details/compressor-50ltr-direct-drive-3-0hp/34121/

Do you think it will handle a die grinder?

w3
01-04-2010, 05:11 PM
I have a 3.5HP honda with a two stage pump on it and my die grinder just kills it. Those tools eat air like there is no tomorrow. HP to HP I believe electric makes quite a lot more air than gas but still it might push it. a lot depends on how much reserve you have in your tank as far as grinding time goes. I am guessing that when you use it you are generally running for extended periods cleaning up castings so the best answer I can come up with is get one and try :) Air tools are pretty cheap (maybe a more expensive one gets more done with less air??? I dunno) and even if it chases the pressure down too quickly in your tank you can still find a use for it in your shop for little quick jobs.

w3

Bob S
01-04-2010, 05:27 PM
Most of cheaper air driven ones use about 4cfm so if your compressor is rated over this then you're OK but on long use cycles you will start to get water in the lines and blowing out the grinders exhaust port. I have a 27 cfm 7-1/2 hp compressor and still had trouble with water condensing in the lines on long days of grinding and then blowing out the grinder's exhaust port. :evil:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47050

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95029


I had one like this one below but because of this water problem even though I was double trapping for it the front bearing was getting water in it and seizing up. Precision high speed bearings aren't cheap either and don't get a right angle grinder either unless you really need one. The one I had burn out the gears in short order. :? Bob


http://cgi.ebay.com/Pneumatic-1-4-Air-Die-Grinder-Sioux-SDG2025_W0QQitemZ310191633892QQcmdZViewItemQQptZLH _DefaultDomain_0?hash=item4838dcb5e4

Anon
01-04-2010, 06:45 PM
I have a die grinder almost identical to the one in the first link. I don't know where they get 4 CFM air consumption, but the word "average" makes me think it's with a duty cycle less than 100% factored in. In practice, my compressor (rated 4 CFM at 90 PSI, 7 CFM at 40 PSI) will run the tool at about a 60% duty cycle before it loses so much pressure that it starts stalling. In practice, this is only mildly annoying, but I'd want more compressor power if I was using it in a production situation.

Water in the lines is a real problem, especially as I don't have any kind of drying unit on my compressor. What I do is oil the tool frequently and generously. This gets the water out of the bearings, but it also sprays a nasty oil/water emulsion out of the exhaust port and onto your work.


And I the cynical side of me sometimes wonder if they are designed that way. Then I think but would they do that as it would damage their reputation in the long run.
Lots of manufacturers design products not to last very long. Some of them have a good reason for doing so (for example, if building to a higher quality standard would dramatically raise the price, there's a place in the market for a cheap entry-level tool that isn't going to last very long). Others do it so they can sell more products, which I think is stupid, but I guess it's profitable or they wouldn't do it. Still others just have bad product designs.

Peedee
01-04-2010, 07:15 PM
I use a cheap, cheap, cheaper than cheap, air die grinder on a small compressor. Uses lots of CFM but you do get a technique for tuning the pressure and the way you use it.

If your compressor and tank is small your going to get peeved with it pretty quick, otherwise you may want to give it a try. Mine cost £20 (around $30) with bits and collets and seems pretty bullet proof.

Peedee
01-04-2010, 07:18 PM
With any large volume of air shifted your going to get water, normal practice is a filter trap and if your just using the line for tools a drip oiler is pretty cheap.

welder19
01-04-2010, 07:38 PM
If your going to go with air powered tools, which is primarily what I have for all of my power tools, then don't buy cheap ones, they don't last and don't have the power that good ones do, I don't care what their advertised specs are.
The brands to buy are Snap-on, Matco and Ingersol-Rand. The price difference is huge compared to harbor freight or Northern or any other cheap tool dist, but you will have to replace them enough that you will end up spending as much as you would have if you just bought a good one.
I have made my living as a diesel mechanic and used tools every day all day and can tell you first hand what is worth it and what isn't.
And I know what a lot of guy's say "I'm not making a living with them so why spend all that $$$", well it's because you want the tool to do the job that you expect it to, cheap air tools have no power and consistently stall out. That is why you hear a lot of people say air tools are not the way to go, it's because more than likely they have only used cheap ones.
Also if you want them to last you have to use a water seperator in line to keep the water out of the tools, I have some air tools that are worth over $700, I'm certainly not going to let them get water in them over a $100 and some odd dollar water seperator.

welder19

nudge
01-04-2010, 09:49 PM
Ive been looking at some air die grinders on ebay that has 3mm (1/8") and 6mm (1/4") collets so I could still use the dremmel burrs and stones with it. Anyone has experience of air versus electric. Are they long lasting? could they deal with agressive grinding of bronze? Any brands to recommend
Thanks everyone for your advice.
I have a 1/8" Air "dremmel" and a 1/4" one If the job is dusty takes a long time I use them :) but if is a quick sand or I cant be bothered starting up the compressor then I use the standard electric one :lol: the air should last just keep the oil up in them :)

mantrid
01-04-2010, 11:00 PM
Most of cheaper air driven ones use about 4cfm so if your compressor is rated over this then you're OK but on long use cycles you will start to get water in the lines and blowing out the grinders exhaust port. I have a 27 cfm 7-1/2 hp compressor and still had trouble with water condensing in the lines on long days of grinding and then blowing out the grinder's exhaust port. :evil:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47050

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95029


I had one like this one below but because of this water problem even though I was double trapping for it the front bearing was getting water in it and seizing up. Precision high speed bearings aren't cheap either and don't get a right angle grinder either unless you really need one. The one I had burn out the gears in short order. :? Bob


http://cgi.ebay.com/Pneumatic-1-4-Air-Die-Grinder-Sioux-SDG2025_W0QQitemZ310191633892QQcmdZViewItemQQptZLH _DefaultDomain_0?hash=item4838dcb5e4


Cant believe how cheap those grinders are there. The cheap ones here in UK are about £20 going up to over £100 for a quality one. Definately a case of rip off britain as we say here.

w3
01-05-2010, 12:58 AM
Definately a case of rip off britain as we say here.

I would think more like economies of scale but then I dunno, maybe the world really is out to rip off britain.

w3

ToddW_00
01-06-2010, 07:17 PM
I hate those type of appliances that break a few months after the warranty runs out, like they installed a timer in it or something.

My sister in law has a good trick for warranties that have expired.
Buy an identical product in the same store. Return the old product under the new warranty to get a new one.

You now have 2 new products, or at least one new and one repaired. If the store has a return policy you can even return one of them for cash or a coupon.

On the surface it sounds unethical but I have to go with it. Too long have we tolerated junk product for quality money(currently but going down the path of junk.) Getting the junk returned promptly will in the long term inspire quality.

They make electric die grinders but they're so huge. Anyone know of something between a Dremel and one of these? (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44141)

4cylndrfury
01-06-2010, 07:35 PM
i dunno, but $30 for the HF grinder is a pretty smokin deal. Ive heard of people doing some minor tweaking (usually replacing plastic washers with metal, adding grease here and there etc) and those HF tools can last a long time.

mantrid
01-06-2010, 08:27 PM
Wish we had those harbour freights here in the UK, They sell some seriously cheap stuff.

Good news with the dremel, it has a two year warranty and free collection and return. It went back yesterday. Hope they cant tell Ive opened it up as I think that probably voids the warranty. There was no resin or plastic over the screws and no 'void if removed' label so I could be ok.

Sylar
01-06-2010, 09:00 PM
I hate those type of appliances that break a few months after the warranty runs out, like they installed a timer in it or something.

My sister in law has a good trick for warranties that have expired.
Buy an identical product in the same store. Return the old product under the new warranty to get a new one.

You now have 2 new products, or at least one new and one repaired. If the store has a return policy you can even return one of them for cash or a coupon.

On the surface it sounds unethical but I have to go with it. Too long have we tolerated junk product for quality money(currently but going down the path of junk.) Getting the junk returned promptly will in the long term inspire quality.
That is basicly the same idea why I have on the subject.
If you paid good money to expect a quality product and they give you junk, it's okay to rip off the company who ripped you off.

mantrid
01-08-2010, 09:45 PM
Very impressed with dremel. Box arrived today with a brand new dremel. They upgraded me with the new 4000 (175w) which is more powerful than the 400 (140w). They also included a nice case and a flexi shaft, I only sent them the machine. I have two of these flexi shafts now. Ill be more gentle with this one.

nudge
01-09-2010, 12:52 AM
That IS a good outcome 8)