I stripped my Bosch 10.8V drill/driver yesterday. It's one of these (GSR 12V-15):
Sorry there are no pics but I used the kitchen table (so had to hurry). To disassemble, there are a number of Torx T9-headed self tappers between the two clamshells, and one U-shaped clip at the open end of the battery compartment, which can be hooked out with a flat-bladed screwdriver used on edge. The drill comes apart easily, and the motor separates from the gearbox without issues and can be disconnected from its power leads without unsoldering.
I am quite impressed with the design and engineering (despite the very sloppy chuck/shaft). The motor is _very_ chunky for the size and has extremely strong magnets, but it is still well magnetically shielded. I'm not too impressed with the quality of the high-current soldering (thick motor wires that looked dry-jointed), but didn't interfere in case I made matters worse. The board connections were sound though.
I think the intermittent starting problem was a loose connection to the rear of the motor (Lucar spade connectors). Squeezed them a bit tighter, and now it's fine. It's apparent that the high- and low-current (control) circuits follow rather different routes, so it's quite possible the control side was fine but couldn't get enough drive to the motor because of a poor connection. There's no obvious feedback from the motor to the controller, though it may do current sensing through the power connections.
The switch is very complex, and I think it's low current at the trigger, so not directly responsible for the issue (as I'd originally feared). You can still buy the board and switch combination as a spare part (around 25 quid). It would be an easy repair if it was needed.
I cleaned everything and added quite a lot of grease* to the planetaries on the gearbox input side as (a) they looked a bit dry, and (b) they were easy to get at, also to the speed change actuator where it enters the sides of the gearbox housing. Thoroughly cleaned all the sliders, etc I could get at too, and the motor cooling vents.
I don't think it's quite as good as new (it is eight or nine years old, now), but it is running smoothly and quietly again and the speed change and torque clutch both seem to work fine.
This is the second series of Bosch cordless drills where I have really struggled (and failed) to release the chuck. I tried several approaches, including gripping a large Allen key in the chuck and hitting the inside of the key with a spanner (along the shaft axis!). Couldn't get it to break free. Do the professionals use a puller of some sort? There's a dust trap right behind the chuck on this one that might make that difficult. Previously, I just undid the LH threaded machine screw and the chucks came free easily, but not so any more, it seems. Bright ideas for chuck removal greedily considered, as I would have liked to clean/grease the clutch, but couldn't.
All-in-all it seems well made and serviceable without special tools (apart from the chuck!). I don't know about the current ones - these are still available but the current designs all have a ridiculous hammer-action function that I don't want. The motor is particularly good, and an obvious area for cost reduction if they've been doing that. Just sayin'.
E.
*Castrol high-temp lithium, as it's all I have handy. probably the wrong stuff, but seems to work for most tasks and doesn't dry up easily.
