Bosch 4000 table saw fix (momentum lost and found)

So it's been 10 days or so and the parts for my Bosch 4000 table saw have finally arrived.....time to bring the beast back to life. As you may remember, it had been making peculiar noises, off and on, for a few days prior to me actually deciding to do something about it, rather than burning the thing up. I have been known to actually be proactive, on occasion, regarding maintenance but generally the opposite is true. That must explain my ability to fix things. Practice!

The saw had been making a chattering, rattle-ly noise (bad bearings or field windings) concurrently with the motor dropping in RPM's (bad motor speed control, bearings, brushes, armature or field winding) and there was sparking visible through the motor dust shield ( bad brushes or armature). On dissasembly, the brushes weren't too bad, the armature appeared fine, but the tail bearing was worn and discolored as was the field winding. When I was messing around with the saw, trying to figure out what was wrong, I briefly disconnected the speed control, but that had no effect on the speed or chattery noise, so I figured that the speed control wasn't the culprit. When the speed control fails, the speed either goes too high or the saw actually runs slow or backward.

These saws (and the newer 4100) have a history of motor problems, with the field winding and electronic motor speed control being the most common points of failure. If you go to an online tool parts supplier like toolpartsdirect- Bosch 4000 saw you will see a list of the parts available, as well as the most commonly ordered parts. Very helpful. I ordered all of the most commonly replaced parts, because we all know what happens if we only get what we think that we need........

Have you looked under your saw lately?

Here is where we left off. First remove the brushes and the three screws holding the dust cover in place. Take note of the wiring connections and separate them.

Just a 4 screws to remove the case

Keep track of the parts

3 jaw puller (the bearing came off easy)

I prefer the one on the left

Fancy tools, very sophisticated

Many light taps. I used a socket to keep from damaging the new bearing race.

New field winding

Don't do this!

The tail bearing sits in a rubber bushing/seal cup, probably to allow for slight miss-alignment. I first put the rubber cup on the bearing, then put the case back in place, but the cup felt like it was getting in the way. Instead, I put the cup into the motor case bearing housing, THEN slipped the case over the armature and all was good. Also, the windings would have rubbed against the armature so they needed to be carefully (hahah) adjusted with a pliers (bent out of the way). This makes me a bit skeptical about the longevity of the repair or the overall quality of the parts. And these were real Bosch parts BTW.

No sparks!

Test run. A very few sparks and no chattery noises and the speed was good too. It looks like it was only the motor field winding that was causing the noises and speed fluctuation (although the bearing did need replacing, too). We'll see how long it lasts. My fingers are crossed.

Momentum lost

No sooner do I really get going on a project that I've been putting off for far too long when........*Sigh*........my table saw starts making funny noises and spitting sparks.

Bosch 4100 (Mine is the 4000)

 This is a picture of the newer 4100, but it evidently has the same issues, which is a poorly built motor field winding assembly. When this starts to go bad, you will hear the motor kind of stutter, rpm's go up and down, often hear a chattering noise and see lots of sparking underneath the motor dust cover. The bearing in the armature tailpiece often goes out too, talking the plastic motor case with it. And the motor speed control often has issues and does things like make the motor run backwards and stuff. This is a $600 saw, not that I paid that much for it, and I would be PISSED if my 1 year warranty had just expired. I, of course, bought mine used off of Craigslist for $70 with a stuck lifting mechanism. Oh yeah, it has the least effective dust collection system out of any tool that I have ever seen. The old saws in my highschool wood shop had better dust collection, and they had NOTHING! At least they dropped their dust on the floor. This one throws it in your face and the front of your pants. That IS with the vacuum hooked up!

What do I like? The aluminum table is flat, the blade is square to the slots, and the fence works well and is tolerably sturdy. It has a "soft-start" which should prolong motor life (hahhahahah) and the wheeled stand is sturdy and works very well. The right side of the table is a sliding extension the allows you to rip to the middle of a 4x8 sheet and the fence still stays square. the arbor/shaft thing has NO wobble and it makes great, accurate cuts, which is more than I can say for a lot of saws. I also have a basement workshop, so I don't have very much room at all, much less a REAL table saw, and this one is nicely mobile. If only the damn thing didn't smell like bacon frying.

Devil blade

 Buy good blades. I think that the Freud lineup is a good value, and the Diablo's are good enough for most users. I would suggest that you also buy a spare motor while you are at it, but Bosch doesn't sell them. The parts for my fix will run $100 from http://www.toolpartsdirect.com and I don't even need to replace the case.

So where does this leave us?

Not much under here, is there?

Smells like barbecue

The picture make it look worse than it looks in person, but there is some discoloration and some of the insulation looks kinda melty. It is pretty easy to get to, just turn the saw upside down, tilt the blade, three screws on the dust cover to peek, then four screws to separate the case. Pull the brushes before separating. Well, since I am doing tool rehab for the next few days, I might as well do more than one.

Old friends

The old DeWalt sander has lost it's grip (on it's pad) and both have a bit of bearing noise. These are easy to work on.

Dust much?

MANY hours of sanding nasty fiberglass on my various sailboats. I have cleaned this before, just not in the last few years. I got the big gun, Metabo SXE 450 6" sander, so I don't use this one too much anymore. Still, since I am in repair mode, what the heck, all it needs is a new sanding pad and a pad bearing. The brushes haven't reached the wear mark yet, so dust it out and it's good to go. The parts won't be here for a few days yet, so I put everything back together while it's still fresh in my mind and that way nothing gets lost.

Replacement mark on the brushes

Bad Bearing! Bad!!

 This is the noisy bearing. Not too surprising after god knows how many hours  of really nasty work. I bought the sander about 25 years ago, have used it more or less steady since, and once you accept that the non-marring soft-start pad brake thingy is a 10 minute disposable item, I have no complaints. Well, the dust collection sucks.

Chipped edges

These are the brushes from the DW670 laminate trimmer. This tool is also about 25 years old, still gets used all of the time (my big 3 hp router just collects dust) and is a favorite tool. The brushes still have some life left, but are a bit chipped on the edges, so for $10 I'll replace them. While I am at it, the lower main bearing sometimes seems a bit loud, so I'll swap that out too. If you use bits that are dull (who, me?) the base of the whole tool can get a bit warm which just adds to the abuse that the lower main bearing has to take. Time for a new one. A while back I made a bigger base for the unit and also took the time to correct the out-of-square base adjustment. I always just took it for granted that the trimmer would cut just a teeeeny bit more if you hold it one way or another. After 25 years and 15 minutes, it finally cuts evenly. I should be more embarrassed.

As I said, the parts won't be here for a few days, so I'll show you the actual replacement later. Time to work on some other tools. Kanna re-hab, anyone?