What is the thread size of the spindel on the Dremel MultiPro 395 type 5?

SOURCE: switch

Definitely not Home Depot. Try googling 'dremel model 395 switch', you'll probably come up with something. If not, there's always dremel themselves. This is a current model so there shouldn't be any real problem getting parts.
Sorry, don't know about installation, but I can tell you most of these dremels are real easy to fix in general, not complicated at all.

SOURCE: need new variable speed switch for dremel 395 type 1

Someone else recently asked the same question and got the following solution;

http://www.fixya.com/support/t1515699-variable_speed_switch_dremel_395_get

SOURCE: Dremel Model 395 Type 3 Plastic Drive Shaft

You can call Dremel direct at 1-800-437-3635 and order the part. Let me know if you need more information.

SOURCE: I own a Dremel model 395 type 5 variable speed and

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.

SOURCE: dremel moto tool model 395 coupling from motor to

The part that goes between the motor and the chuck is called the CLUTCH UNIT,
REF 2615294309 it is a splined rubberised sleeve, it also fits the 276 and 396.
The price is £3.69 (including vat at17.5%) and can be obtained from Jaymac (Derby) Ltd.
http://www.dremel-direct.com/acatalog/service.html