Replacing the motor in a Dremel 8220 cordless rotary tool

The Dremel 8220 cordless rotary tool is often my 'go to' tool when I'm making or repairing things. I use it mainly for cutting, sanding, and grinding, mostly with steel, plastic, and wood.

I've had it for many years, and it's had a lot of use. Recently, it started making a very unpleasant screeching noise, along with a noticeable drop in speed. I could still finish my jobs, but after a while it got annoying, so it was time to take it apart and have a look.

Disassembly
The body is a standard plastic clamshell design, which needs the Torx screws removed, and also a U-clip which can go unnoticed unless you have a good look.

Once apart, it's easy to see what all the parts do, including the spring-loaded shaft lock button that engages with the toothed motor rotor.

Diagnosing the fault
Initially, the motor looked ok but it wasn't until I looked at the terminals end of the motor that I could see the motor shaft was off-centre. The internal bearing had failed and whenever I moved the tool or applied a load, the shaft would oscillate off-axis. The imbalance created the intense vibration and that horrible screeching sound.

The inside of the tool housing had a lot of white dust. This would have been from Gib plasterboard getting into the tool while I had been cutting downlight holes overhead. The dust is quite pervasive and abrasive, so I'm not surprised the bearing failed, especially with how many holes I had done.

The repair

1. Install a new motor: Plugged into the existing terminals.
   
   
2. Reassemble the shell: Taking care to correctly seat the lock pin spring and the on/off switch etc.
   

Testing
Of course, in my excitement to get it put back together, I didn't pay close attention to the polarity of the motor, and when I fired it up, it ran in reverse! It seems that all too often when you have a 50/50 chance to get something like this right, you'll get it wrong...

At least taking it apart was a lot quicker this time. I did that and reconnected the motor with the correct polarity.

The result
After putting it back together for a second time, it's now running super smoothly. It feels like a brand new tool again.

The economics
The replacement motor cost me $99* incl GST, and it was a quick and easy repair.

If I replaced the whole tool, I'd have to buy the refreshed version of the 8220, the Dremel 8240, priced at $199* incl GST.

For me, if a tool is still doing the job, then I'm happy to fix it instead of throwing it out. If the casing was getting tired, and the electronics were failing, and the parts were going to cost more like $150, then I'd look a bit closer at buying a new tool.

At under $100 and some of my own time, I feel like the repair was good value and I have the satisfaction that the 8220 lives to see another day.

Dremel 8220 Spare Part Number 2 - Motor 2610005460 $99 incl GST*

Dremel 8240 12V Rotary Tool Kit 8240-5 12V F0138240NA $199 incl GST*

* Prices correct at time of writing.