bosch oslillating multitool MX30EK gets hot!

13 years ago

Hi,

Loved this tool! Used it almost non stop during my kitchen remodel. Then one night I was cutting wood (a 2 by 4 that needed a notch), the pitch changed and the cutting speed dropped. I finished with a chisel and picked up the tool to investigate and it was hotter than when I was using it. Not quite to hot to hold but approaching it.

I immediately unplugged it and plugged it in again the next day, again it got quite hot.

I contacted Bosch and they said they would fix it free of charge ( i think I would be stuck for shipping and out the tool for a few weeks).

I ended up returning it to Lowes (90 day return policy, few questions then refund to my card). If they had had one on hand I might have taken a replacement. Now considering a Fein.

This is a great tool for remodeling, cutting drywall, wood metal. Cutting studs away from siding by cutting the nails. Ok for demo pipe but leaves very rough edge. Plunge cuts! Sanding! But possible burning down the house problem not so good.

hope this helps someone.

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Comments (7)

sombreuil_mongrel
13 years ago
Hi,
I have had the top-dollar (and superb, BTW) Fein Multimaster get literally too hot to handle under heavy prolonged use on a warm day. The mechanism has a lot of friction in converting rotary motion into back/forth motion. Hopefully the grease used in the Bosch is as well-suited to the task as the lube in the Fein.
Casey
drake64
Original Author
13 years ago
Thank you for your comment but I think you misunderstand.

While the tool did get warm while running (I would not say hot just warm). My concern was after the tool was turned off it got hotter. The next day I did not turn it on at all just plugged it in and the unit got hot.

I did not take it apart as I was not sure they would take it back but suspect a failed cap (failed short rare but possible) or failed regulator. Also possibly a trace or wire shorted for some reason, usually poor design or quality control. If design it will definitely show up in other units if quality control probably just batches.

I only left it on for a few minutes (less than 5) it was continuing to get hotter (I think, I just measured by feel without a temperature gauge) until I chickened out. I guess it would have been interesting to put it on some rock and see if it would burst into flame or melt.

Bit concerned the company had nothing to say. Possible that it was a only failure. Also possible they are covering up a problem. I dont know which but I think I will try a Fein.

Respectfully,
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User
13 years ago
You are using a tool designed for hobby type use in a commercial industry manner.

You burned out something. If you use the new one in the same manner, it will fail also.
drake64
Original Author
13 years ago
Hmm industrial use? Im one fellow remodeling his kitchen.

I used it for 3 weeks.

Im afraid I must disagree.

I just want folks to know it is a problem. If no one else is having a problem than its a one off or just me.

Im glad you are happy with yours. Thank you for sharing your opinion.

Good luck.
sombreuil_mongrel
13 years ago
Hi,
Two points:
Maybe it is just "heat sinking" which means the stored heat keeps coming off the tool gradually and is exacerbated by having the internal cooling fan no longer blowing.
BUT if the heat is by the speed control/switch, and it smells electrical, then there may be a caution.
Casey
brickeyee
13 years ago
Sounds like a shorted stator winding.

Most of these tools use smaller 'universal' (AC/DC) brush motors since this allows for simple speed control, or a stepper motor that is more complicated to control but often has wider speed range.

They have been able to gain power lately by using newer more powerful permanent magnets to supplement the stator winding, or even in the rotor.

You could have cracked a brush or shorted out a portion of the winding.
This allows the device to pull excessive current and typically makes them run at a slower speed.

Replacement of the damaged winding is about the only fix.

This post was edited by brickeyee on Mon, Jan 21, 13 at 13:28
User
13 years ago
Has to do with something called duty cycle. Tools designed for hobby work---which the bigger percentage of those multi-tools are-----have a very short duty cycle.

That is the maximum time a tool is designed for continuous use under load.

That is why real professional grade tools are so expensive. Because the maximum duty cycle is designed into the tool.

Like the difference between plastic picnic flatware and metal flatware. The plastic spoons/forks/knives can be used the same as the metal ones, but their life span is much more limited.