The postman brought my bearings today. Now that I have them its time to put my Milwaukee drill back together. Here’s what was in the package.
I pulled the bearings out and compared them to the old ones. Sure, they should be the same but it’s good to check.
Someone on owwm.org recommended I clean the commutator and suggested a commutator stone for the task. The carbon brushes ride on the commutator and over time can deposit carbon on the commutator. The stone is a relatively soft white stick that removes the carbon from the commutator without removing copper when rubbed against the commutator. The commutator is shown below on the end of the armature. It’s the slotted copper ring. I didn’t get every trace of fowling from the commutator but removed most of it.
I started reinstalling bearings by putting the rear armature bearing back in. I triple checked that this was the correct bearing before installing it. The bearing on the front of the armature is the same outer diameter but has a different bore size. It’d be easy to put the wrong one in. I put the bearing in place and then tapped it home with a wooden dowel and hammer until it seated.
Next, I pressed the front armature bearing on. The previous bearing left a print on the surface of the polished shaft that I used to determine how far to press the bearing on. In the future I should take measurements on disassembly. I should know this by now.
I used my arbor press to press the armature into the rear bearing. I pressed it in until the brush sat in the previous spot on the commutator.
I cut the old cord off because it was dried out and cracked. I checked around online and found a few sites when supposedly had replacement cords. They wanted $25 so I decided to use a regular cord from a local store. The problem with using a normal cord is that it lacks the thick molded rubber piece that functions as a strain relief. The strain relief keeps the wires from being ripped out of the drill when it is tugged on. I decided to get a rubber cork and try fabbing one up myself. The first step was to put a hole in it for the cord.
I eventually found the right size hole and was able to tug the cord through the cork. It didn’t go in easily and I don’t think it’ll pull out with serious effort. I put a zip tie on the cord above the cork to some additional holding power. The zip tie had to be cut off later though because it didn’t fit in the plastic handle.
I soldered the new cord to the old wires in the drill and used my multimeter to make sure that every everything was wired up correctly. I checked for continuity between the cord’s prongs and the brush pockets with the drill’s switch in the on and off positions. Everything checked well.
I finished off the soldering with some heat shrink tubing to make it look neat and protect against shorts.
It turned out that the hardest part of the rebuild was getting the wires stuffed back into the plastic handle halves. The solder joints are stiff and the wires are probably a little longer than before. All this added up to wires that didn’t want to fit where they’re supposed to. My rubber cork also needed a little trimming with a razor blade. It was larger than hole in the case even when compressed. After a little adjustment it fit tightly.
Now it’s time to reinstall the diaphragm. This was pretty easy even though the front armature bearing is pressed into it. You can use four screws to draw it into place by incrementally tightening them. While I still had screws in I pugged the drill up and ran it. It’s much quieter now and ran smoothly. Note that the bottom two screws in the diaphragm have to be removed to install the gear case.
I put the bearings on to the spindle making sure to reinstall the shim between the gear and rear bearing. For some reason the new rear (left in the pic) bearing’s bore was slightly larger than the old one even though they’re the same number. I used some green Locktite to fill the gap between the bearing and spindle. I’ve done this on previous machine rebuilds with no ill effects.
Before putting the spindle back in its time to put the grease back in. I used some Mobil synthetic rear end grease. I wasn’t exactly sure how much to put in but tried to put in as much as there was before. I doubt an exact amount is critical.
After that the chuck is put back on and I’m finished! Well, not totally. I put a little paint in the recessed logo on the sides of the case.
It drills holes pretty well as you’d expect. It does slow down some with a larger bit because its not a large drill. The drill seems quieter than before when holding it in midair and running it. With the spindle reinstalled the gears make the drill louder than when I ran it without the spindle installed which is expected. There’s still the occasional rattle that I assume comes from it being a metal case. When drilling though it was louder than I thought it should be. The noise sounded like it was coming from the front near the gear. I took the gear case off again because I remembered there being a little rubber plug in the diaphragm that looked like it could press against the rear spindle gear (you can see it the the 5th pic above from here). The plug is made out of rubber and had flattened on one side. I spun it around and reassembled the drill. When I tried drilling again it seems this had quited the drill down some. I took the case back off and added a little more grease but it didn’t seem to make much difference. One thing that I wasn’t expecting is that after using the drill for a little bit it gets pretty warm. It’s not painfully hot but you notice it. I guess that’s another side effect from the aluminum case. Also, I think I’ll keep an eye out for a replacement 3/8″ chuck. The current one doesn’t grab the bit well and allows it to slip some. The holes were the chuck key goes are also worn pretty heavily.
Here’s a side by side, before and after pic. I’m happy with how the drill turned out and will be putting it to use in the future!