Hitachi M12V Speed Control

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Forum topic by Rich_LI posted 01-17-2022 04:06 PM 659 views 0 times favorited 2 replies Add to Favorites Watch
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57 posts in 3416 days

01-17-2022 04:06 PM

Topic tags/keywords: m12v router speed control speed control tip router

Like allot of Hitachi M12V users my speed control has been acting up, sometimes the speed varies on it’s own, sometimes when it’s hot the router wont work at all. I have researched it and read all the blogs, one web site claims to have the part,

But at $102.50 and $19 shipping, I think I would purchase a new router. The consensus is to use a HF router speed control, everyone that uses one says it works, however, it does not have speed feedback that will keep the router from bogging down when under heavy load.

So I purchased the Speed Control, but before cutting the wires inside my M12V I figured I would try to fix it. You can not take the speed control apart because it is a potted assembly. I wonted to try to clean the wiper fingers under the speed control knob, since I had nothing to loose I drilled a hole in the top and spray tuning cleaner inside and work the knob back and forth to clean the fingers. This worked marvelously, the router is working great and I have the external speed control stored away, hopefully never to be used.

The 3 pictures the first you can see where I drilled the hole, I used a 1 edge razor blade as a depth gauge to measure how deep the the internal shoulder was, then marked this with a pencil (you can see the mark). Then I carefully drilled the hole with a 1/8” bit (this was larger that I wonted but the tube on the spray cleaner was large). I chucked the drill very loose, so when it broke through it slipped in the chuck, I then took care not to drill too deep. When I finished, I was looking at the wiper I needed to clean. I sprayed the tuning cleaner (this type of cleaner also has a lubricant) inside and worked the knob back an forth. I then turned it upside down to drain it and hit it with compressed air (from a distance), the cleaner came out the sides through what I assume is an Oring. I then cut some aluminum tape (with a washer as a guide) and covered the hole. While I was at it I took the router apart and cleaned and oiled the slides because my plunge action wouldn’t bottom out any more (be careful not to loose the brass lug that binds the stop leaver). When I first tried the router it didn’t start, I had to work the speed control knob back and forth, it started and hasn’t stopped working since.

Happy drilling

-- Rich LI, Life is short, buy more tools !

2 replies so far

View bmwaits's profile


8 posts in 2353 days

#1 posted 02-09-2022 11:45 AM

Hi Rich_LI – Thanks for posting this. I had an incident with my Hitachi M12 yesterday. The collet lock had gotten stuck and I didn’t realize when I turned the router on. It made a humming noise for a few seconds before I realized what was happening. I shut it off, loosened the collet lock, and tried to turn on again… and nothing. I’m not exactly sure what happened inside, but I’m wondering if I burned up the speed controller board. Thoughts?

I also searched the web and found the same overpriced replacement controller. You mentioned the HF controller. Do you have any more information on how others are configuring that to the M12?

Thank you for any thoughts you may have on this situation.


View Rich_LI's profile


57 posts in 3416 days

#2 posted 02-09-2022 02:42 PM

To determine if it is the speed control, you can bypass it. When you bypass it is will go to full speed, if this works its the speed controller and you can either let it stay full speed or use an external controller. I am not sure my method would work seeing that you may have either burned up some electronics or the windings of the armature as opposed to this being a case of dirty wipers on the controller. Here is a link to bypass the controller. But basically there is a wire in and a wire out, you just connect these two together (there is also a smaller speed sensor wire that you dont have to worry about)

-- Rich LI, Life is short, buy more tools !

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