Finally fixed Bosch 4212 miter saw squaring issue after all these years of frustration

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Forum topic by Holbs posted 10-28-2018 03:15 AM 979 views 0 times favorited 2 replies Add to Favorites Watch
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2259 posts in 2634 days

10-28-2018 03:15 AM

Topic tags/keywords: bosch miter saw square

No…didn’t throw it out :) Though, it came to mind.
I bought this “refurbished” Bosch 4212 12” compound non-sliding miter saw when I first decided to get into woodworking. I did not know nor care about anything precision related, as I do nowadays. When I did try to make precision square cuts, they came out “mostly” square, as in good enough. Until I started getting into projects that required squareness. I tried to align the fence 90 degree square to the blade. It looked at at the time til I made cuts. Maybe 1/32” over 2” out of square. I lived with it for awhile. Til now. Almost was going to pull the trigger on the Bosch GSM 12” glide miter saw but thought if I could find a way to make this 4212 100%, even better.
The issue is the fence could not angle any more to close that 1/32” gap over 2”. I thought about…why? Surely, Bosch engineers considered this and is why the fence moves as it does, but not far enough in my case. Again…why my case? I looked at things more closely and tore the base apart to see if there was dents or bends or something amiss (always wanted to).

Here is what I found:
the pivoting arm itself is crooked. I would say…1/8”-1/4” out of whack.

How did this come to be? Maybe it was this way when I bought it and never realized. Or…maybe…the locking pin on the pivot arm is the culprit. I always thought you were to lock the arm down with the left side locking arm pin and use the carrying handle on the pivot arm to move the miter saw around. The instructions clearly states this is an acceptable alternative method from grasping the left/right tables to lift & move. What if…this causes the pivot arm to warp/deflect? This is not iron steel, after all. That is alot of pressure/torque on the arm locking pin against the pivot arm.
I cleaned, lubed the base ring, and assembled everything back together. Did not notice any way to adjust the pivot arm. So last ditch effort…what could I do to the fence even though it could not rotate anymore to where it needed to. Hmm…elongate the holes even further. Wouldn’t have to be much…maybe 1/32” or 1/16”. So with my round file, I did just that. And whalla…perfectly square to the blade now! whoopie! Downside is I can not get a socket on the fence bolts because they are too close to the sides. I have to tighten down and tap the fence with a rubber mallet to get square.

Best I could come up with to save this miter saw.
Still would love 12” cut capacity, but I have a couple other things my wallet needs to pay attention to for the moment. Maybe one day.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter "xylokopos/ξυλοκὀπος"

2 replies so far

View lumbering_on's profile


578 posts in 1095 days

#1 posted 10-28-2018 03:27 AM

Nice bit of detective work.

Unless you have to move the fence, sounds like you have a pretty permanent fix. I’d call it a day and grab a beer. :)

View fly2low's profile


88 posts in 702 days

#2 posted 10-28-2018 06:10 AM

nice save on that saw

-- Rich Gig Harbor, WA

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