General > General Technical Chat
Rotary tools in support of electronics, Dremel and more ..
robrenz:
I have a Dremel Professional model #398 that has served me well for the last 8 years with no problems. It is better constructed than the cheaper models. But it is a retired model.
Like saturation says these have real motors in them.
http://www.ereplacementparts.com/dremel-398-f013039807-corded-multitool-parts-c-15440_15456_15477.html
saturation:
Yes, you are right.
I've seen it on factory new boxed models too or poorly reassembled by users: the cap isn't screwed on correctly so as the brushes age the tension of the spring isn't what it should be, causing it to loose contact prematurely or provide uneven pressure on the commutator, so the brush errodes unevenly.
The older models with stiffer plastic or even metal screw caps were more reliable, but the new soft plastic caps can be screwed in improperly. The good news is the cost cutting by Dremel can't go any further since the chassis needs to be rigid enough to support the bearings, so the chassis is pretty much that from the 1992 version, and similar quality.
On bad thing Dremel did in the 1990s was use a Bosch "safety" feature, a plastic clutch connecting the motor to the drive shaft. With overloading, this 'flex coupler' would break severing the shaft from the motor. Alas, with just age all these coupling meant guaranteed failure! As it wore with use, it would slip, reducing speed! Its easy to repair, just insert a new one or until it arrives, use a piece of aquarium air pump tubing, but you have to be comfortable opening the unit, like we all do on eevblog, "take it apart".
If you send those older Dremels in for service, they will give you free of charge add the new motor assembly, about $20, which does away with the coupling, or you can have a supply of couplings, $2@.
IIRC, all Dremel rotary tools use the same proven old motor design, what's been unfortunate is cost cutting in some parts harmed their reputation, and so did using the dreaded coupler.
The Dremel 4000 seems like a good unit, but only time will tell. But I think the simpler 275 aka 100 is a better deal for reliability and expected performance of a Dremel rotary tool.
--- Quote from: DaveXRT on July 13, 2012, 06:21:25 pm ---Or it can be due to stress from incorrect brush tuning- Actually, i mean positioning
--- End quote ---
robrenz:
Went to home depot to try out the Milwaukee unit I mentioned previously in the thread. Very disappointing, with nothing in the collet it has that sick resonating sound at all speeds. It may be gear noise but it even feels bad in the hand. The spindle can be flexed laterally at least .020" in the housing with mild pressure. I could not find a position where the "ergonomic shape" at the nose could be held pencil style. I am sure the motor and electronics will hold up in typical Milwaukee style but I think this is a total FAIL!
Kremmen:
Well, since the question included the word _quality_, my vote has to go to Kress. (please copy the link into your browser; Kress has stupidly included characters in the URL that this forum misinterprets: http://www.kress-elektrik.com/Power-tools.71+M561855e446b.0.html?&tx_commerce_pi1[catUid]=17 )
While i am not familiar with all the brands mentioned, those that i do recognize and own, do not come anywhere near Kress quality. The models i linked are quite popular in CNC circles as spindles for mini mills for wood and aluminium, as well as PCB work - drilling, isolation routing, v-grooving etc etc. High quality collets are available for all popular shaft diameters making a Kress a good allround tool. If only it could do 60 000 rpm as well...
T4P:
60,000 :o You might as well use a mini jet engine :P
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