Replacing brushes in your 36v Bosch Rotary Hammer

I bought a beat to death 11536VSR with 2 good batteries for $160. I assumed it just needed brushes. Common symptoms is a drill that doesn't turn, turns sometimes, has less power than normal, varies in speed / power... To be honest, if there's any problem with the drill turning, check your brushes first. Here's a quick and dirty walkthrough to swapping them.

OE part number for brushes is 1 617 014 412, and I picked a set up for $13 shipped. You'll need a t25 Torx bit and a Phillips screwdriver to get this done.

Start by taking all the black Torx screws from the right side of the drill, as well as the two silver screws that run from the front of the drill, through the gearbox housing and into the drill body on just the right side.

Inside is pretty simply laid out. See the brush holders on both sides of the motor's rotating assembly (armature)? There's 2 small Phillips screws on each that take those off.



My brushes were beat. The surface they ride on is also ruined. I turned the commutator down to even that surface out, so we'll see how long that lasts. If you open your drill up to see this, set aside another $100 to replace the armature.



I took a picture of the next step but my phone lost it. You do not have to remove the spring to replace the brush... Slide the old brush back and push the spring off to the side to hold it open. Slide the new brush in, slide the connector on the terminal and reassemble. When you get to putting the drill body together, be extra careful with the plate that the battery terminals are on. There's a few things you have to be sure to line up there.

Run the new brushes in by gently pulling the trigger to around 1/3 of it's throw and holding it there for about 45 seconds. Do this a few times.

Hopefully this helps someone. Also, be careful with dust around your drill and starting the drill with the bit stuck to avoid excess wear on your brushes and comm.

nice.

Did you replace them?

Walter Galli wrote:Did you replace them?

most industrial type tools have holes in the machine to do this easily within 5 minutes. for some reason, probably because of the compact size, Bosch has decided you need to open the tool to perform this replacement. I'm OK with this, Bosch makes nice tools that work for a long time. Brushes get worked quick by heat that is generated by pushing too hard.

Yep, new brushes are in and comm was hastily turned. There isn't really a good way to chuck the armature into a lathe, so it was rough. I have a new armature on the way, so I'll post that procedure up when it gets here.

Anybody have experience with this hammer losing percussive force? Mine still spins just fine, and when cold, it still has good impact. As soon as it warms up, it doesn't "hit" very well.

I tried replacing the o-ring on the piston and replacing all the grease in the gear case, but it didn't make much difference. There's no obvious wear on any of the gears.

Mine seems to hammer on par with my corded Hilti, so I can't help you there. You were probably into it deeper than I was (I pulled the gearbox apart just to look), but maybe get into it with some brake cleaner to get rid of all the grease and look for wear?

It was pretty dramatic - it was cranking out 1" holes in sandstone one day, then had almost no impact the next day.

I got in there, everything in the gearbox looks pretty good. I kinda thought the piston might behave like a scored small engine cylinder - when cold, good compression, when warmed up, misbehaves. Looks like a trip down to Denver and a stern talking-to from the Bosch service dude is in my future. Will update.