[rhadiem]

I'm having issues with my Hitachi M12VC slowing down while cutting, despite it being set at max speed. I'm doing long 3D cuts with the tip of a ballnose end mill and generally it cuts like a champ but a couple times now it's slowed down significantly, and I had to mess with the speed knob in order to get it going again.

Any clue on what's going on? I've tried googling for it but haven't had any success finding any problems from others on this.

I'm 1/3 the way through an important cut with 20+ hours to go and am not sure what's going on. :tired:

[ger21]

Sounds like either worn brushes, or a faulty speed control.

[rhadiem]

ok I dropped the feed rate to 80% and it seems to be ok now, although if it's an intermittent problem it may just be "sleeping". Any idea how the speed controller works when it's getting bogged down? Would it stay that way for a while unless I change the speed input?

Things are getting deep and the dust collector isn't getting it all so there is generally a thin layer of wood particles on the bottom also.

[CarveOne]

If the router has a lot of run time on it then it is more likely to be one or both brushes. In any case, change them both at the same time. You can remove the screw-in cap to check the brush length. Put the brush back in the same orientation as it came out.

The OEM Replacement Parts | DIY Repair | eReplacementParts.com has replacement brushes for the M12VC router here.

[rhadiem]

I'm curious how worn brushes can occasionally cause a reduction in speed, but then otherwise operate perfectly normally. I've put another 10+ hours on the router and it would occasionally slow down but with some rest or me messing with the speed control it continues to come back up to full speed.

Could it be an overheating issue?

Also, the router has maybe 60-80 hours on it, is this high usage?

If the router has a lot of run time on it then it is more likely to be one or both brushes. In any case, change them both at the same time. You can remove the screw-in cap to check the brush length. Put the brush back in the same orientation as it came out.

The OEM Replacement Parts | DIY Repair | eReplacementParts.com has replacement brushes for the M12VC router here.

[bhurts]

Blow the router out really good with a airhose. If needed take the top cover off and blow out around all the electronics and the commutator. It could just be dust or trash messing with the way the electronics read the motor speed. At 60-80 hours your brushes should still be fine but no guarantee.

Ben

[rhadiem]

Well, after 8+ hours yesterday I didn't have any problems at all with the router.. that is, after I took a small piece of duct-tape and secured the speed control knob.

I think vibrations were wiggling the knob around, causing fluctuation. I'll report back if I have continued issues after this, but hoping this solved it.

Thanks all for the ideas, and I definitely need to pick up some brushes / backup router in the near future.