Bosch 4100 Startup Sound

[Clay Anderson]

Hey folks. I've had my Bosch 4100 for a little over 6 months now, and it has begun to make a sort of... "loose", "rattly" or possibly "grinding" sound upon firing it up. It seems to go away after the first second or so, but it almost sounds like my DA polisher; kind of rough.

Is this a bearing? This soon?

I've found the replacement bearings, but I'm hesitant to use them if they're the problem. I'd rather get some completely sealed Japanese/American bearings and replace them all if that's the case. Unfortunately Bosch doesn't like to give out their sizes...

Exploded Diagrams:
https://www.ereplacementparts.com/bo...167_14496.html

Bearings:
https://www.ereplacementparts.com/ba...g-p-47229.html
https://www.ereplacementparts.com/bearing-p-47230.html
https://www.ereplacementparts.com/ba...g-p-47246.html
https://www.ereplacementparts.com/ba...g-p-47251.html

[Bill Orbine]

Start with a possible loose blade. Make sure it's clean in the dust chute. Other rough startup noise is electrical. Dirty switch, dirty/stuck brushes. You should be able to hear/feel bearing roughness turning blade by hand (unplug saw, of course).

[Mac McQuinn]

I would check all fasteners first for a created resonance by loosening. If this isn't the issue, I would check the bearings, if they have shields that are removable, perhaps you can get some lube into the noisy suspect. They make a injector/needle for your grease gun which should allow you to get lube into place. Have you run the saw hard recently? Heat could have removed some of the factory lube or loosened up a fastener or two.

Good luck,
Mac

[Mikail Khan]

I have had to replace the bearings on my 4000 after 6 years or so of hobby use. Six months sounds too soon for bearing issues.

Bearings are available from any auto parts store.

Noise may be normal from drive gears.

MK