I own a Dremel model 395 type 5 variable speed and it suddenly stopped working. I was wondering if it was common for the switches to go bad or if it's known for other parts to cause it not to turn on.

I would recommend going to Dremel.com and asking their tech section about this. I have one also and mine works fine other than a small amount of heat at the spindle area.

I have the same model and the same problem. It just stopped working after about 1/2 hour running (not continuously, but total time in use). I went to the authorised service and they said faulty switch - $61 (AUS). Not worth it, the new tool is about $80. Next time I buy Ozito - the same tool for just $40.