alignment issue with my miter saw

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Forum topic by mzimmers posted 02-27-2017 07:57 PM 3260 views 1 time favorited 40 replies Add to Favorites Watch
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218 posts in 5154 days

02-27-2017 07:57 PM

Hi -

I have a Bosch compound miter glide saw with a bit of an issue: on 90° cuts, the blade is perfectly vertical, but on 45° cuts, it’s noticeably out of plumb. I can’t find anything in my owner’s manual about this, and frankly, I find it a bit disturbing. Can anyone think of what might be causing this other than a defect somewhere? I’ve had this for years, and just noticed the problem now that I’m making deeper cuts at the 45° angle.


-- M. Zimmers

40 replies so far

View Kelly's profile


3794 posts in 4183 days

#1 posted 02-28-2017 05:45 AM

I have the same saw and the only thing I could think of is, check and see that the bolt on the pivot is tight. I will try to look at mine tomorrow and see if I have the same problem.

Just to be sure, you are saying you’re getting forty-fives, but they are not ninety to the top face or the part that was resting on the table when it was cut?

View issacsamuel's profile


1 post in 1691 days

#2 posted 02-28-2017 06:10 AM

The blade is not a true 90 degrees from the fence. I attempted to adjust the alignment per the instructions in the manual, but there is not enough adjustment in the fence to make it true. adjust 2 additional bolts that will swing the position of the blade. The manual is silent on any additional adjustment step.


View mzimmers's profile


218 posts in 5154 days

#3 posted 02-28-2017 03:15 PM

Hi Kelly -

That’s correct: I’m getting proper 45° angles, but the cutoff isn’t perpendicular to the long edge of the board anymore. I’ll check the pivot bolt and report back later today.

-- M. Zimmers

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218 posts in 5154 days

#4 posted 02-28-2017 09:54 PM

Well, the problem is a little worse than I originally realized.

The picture isn’t great, but it does show the slope to the cut. The bevel is set to 0°, and no such slope occurs when cutting at 90°.

Starting to look like a defective unit, isn’t it?

-- M. Zimmers

View fivecodys's profile


1761 posts in 2875 days

#5 posted 02-28-2017 10:37 PM

My CMS was doing this and I found it to be that the wood was actually moving (drawing) on the bed of the saw during the cut.
Once I clamped the work-piece down during the cut the problem went away.
Not sure if this is your problem but I thought it worth mentioning.

-- A bad day woodworking is still better than a good day working.

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218 posts in 5154 days

#6 posted 02-28-2017 10:50 PM

Hi, fivecodys -

Yeah, I’ve had that happen before as well. I generally use my hand to grip the work against the fence, or sometimes I’ll clamp it.

I’m fairly sure this isn’t the problem here, as the error is too uniform. I just repeated it with a 6” wide piece of 3/4” purpleheart with the same result, so I’m pretty sure the wood’s not bending during the cut, either.

-- M. Zimmers

View Kelly's profile


3794 posts in 4183 days

#7 posted 03-01-2017 01:34 AM

Went out and looked at mine. Check the manual to see what the two Allen screws with locking nuts on the right sliding arm housing do. I’d have to go digging for mine.

I popped the back off (the cover with two thumb nuts and a knob and there are a few bolts there I’d have to double check.

That has to be an easy five if not ten degrees. What happens when you set the bevel for the compound the amount that is off and try a cut? If that solves the problem, it is a set up issue somewhere [I believe].

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218 posts in 5154 days

#8 posted 03-01-2017 02:12 AM

If you’re referring to the part of the manual that discusses bevel stop, I’d point out that the bevel is perfect at 90°. The problem is at 45° left. I can’t do a meaningful test at 45° right because the arm limits the insertion of workpieces more than 1” or so high.

If you’re asking what would happen if I adjusted the bevel when the saw is at 45°, I don’t think anything good would come from that. First off, it’d probably screw up the 90° cuts. Second, to the best of my ability to measure, the blade is nowhere near as far off as the cut indicates. Something is happening during the raising and lowering of the blade.

Here’s another picture. I sent this to Bosch today; we’ll see what they say.

-- M. Zimmers

View Kelly's profile


3794 posts in 4183 days

#9 posted 03-01-2017 02:19 AM

I was curious if adjusting the bevel, say, ten degrees, while cutting a non-compound forty-five, would get the cut close. I was asking only for troubleshooting purposes. If it does, then it has to be something related to adjusting the bevel.

On the piece above, is the large face against the fence or the base when you’re cutting? Assuming it’s a 2×6, I was thinking you were cutting down the face, cutting across the 2” portion.

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218 posts in 5154 days

#10 posted 03-01-2017 02:24 AM

The workpiece went into the saw as this picture indicates. I’m not sure we’re communicating on the subject of the bevel adjustment, but my understanding is that when it’s correctly set, it should be correct for all miter angles. The fact that it isn’t suggests that the arm might be bent. I would really like to be wrong on this.

-- M. Zimmers

View Kelly's profile


3794 posts in 4183 days

#11 posted 03-01-2017 04:22 AM

Thanks for the photo. That removes all doubt about what is happening.

So: – it is cutting at 90 on the 90. – when you turn it to 45 in one direction, you cut down into the wood at 90 degrees, but at an angle, as if the bevel is moved.

Now comes the question, do both 45’s give the same cut, or does it get progressively worse, get better, go in the opposite direction (wider at the bottom than at the top instead of at the bottom)?

And, yes, if you set the bevel, it should be consistent all the way left and right.

View Aj2's profile


4065 posts in 3036 days

#12 posted 03-01-2017 05:59 AM

Your asking too much out of that saw.What is that Purple Heart?
That’s a 12 inch blade so there’s is going to be some movement and the saws is not even close to be ridged enough.
I have one and it cuts very good angle on crown molding and tall baseboards.
But when I start using my saw for hardwoods like hickory it’s very difficult to get consistent results.


-- Aj

View Andybb's profile


3329 posts in 1842 days

#13 posted 03-01-2017 08:10 AM

I’m no expert but I have the same saw and have never had that issue. I was curious so I just did a test cut. But I would always clamp a cut like that. That saw has always been dead nuts accurate regardless of the material. Not sure what your issue is but doubt it’s because of the purple heart. Is the piece square and flush against the base and fence?

-- Andy - Seattle USA

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19343 posts in 2377 days

#14 posted 03-01-2017 01:47 PM

I’ve never had this issue and don’t have this saw but that much variation looks like way too much to me.

Do you have a dial indicator? If so, I would set the saw at 45 where you’re having the problem and zero the indicator at the bottom of the blade then slowly bring the blade down (not running obviously) and see if there is measurable deflection. Repeat at 0 degrees where you get good results for a baseline. This can give you quantifiable proof of the problem if the manufacturer gives you a hard time.

A less precise way to do the same check would be with a digital angle gauge on the blade. Check and see if the angle changes as the blade is brought down.

Either way, I’d definitely pursue a warranty claim.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

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Craftsman on the lake

3882 posts in 4676 days

#15 posted 03-01-2017 01:58 PM

I have this saw. If you’ve ever had a piece of wood bind and kick violently on you it could be the fence. The fence is adjustable and with a lot of pressure will move. The right side of mine actually bent. I should get a new fence but I compensate for now. I like this saw.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

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