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Bosch Miter saw - Just cant get it square

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Forum topic by jonlan posted 11-11-2016 02:59 AM 1275 views 0 times favorited 9 replies Add to Favorites Watch
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jonlan

43 posts in 720 days


11-11-2016 02:59 AM

I’ve been the relatively happy owner of a Bosch GCM12SD miter saw for over a year now. I’ve used the saw on and off since purchasing it but never for anything that really required absolute precision. While I found the default adjustments mostly square, I did notice that 45 degree miters were never quite perfect. The other day I decided to start getting ready for a new cabinetry project. So I thought it would be a good time to finally dial the saw in.

I have now spent 8 hours over the course of two days with the saw and just can’t get the saw to cut accurately. First, I tried to zero the saw in for normal 90 degree cuts. This took a great deal of time and I used several methods to get the saw right at 90. Finally, after a lot of messing around I was able to make a 90 degree cut on a board, flip it over to the other side of the blade, make another 90 degree cut, and when I checked the difference on either end of the piece of scrap I cut off with my caliper I was within a 2-3 thousandths of an inch. I then locked the miter adjustment in (tighten 4 bolts for the miter gauge which slides) and thought I was all set. Then I moved the blade to 45 degree and did some test cuts there. The miter wasn’t even close to being tight! When I moved the saw back to 90 degrees and tested again, I found that I was once again off!

The saga continued for hours and at the end of it, I found that I couldnt even get the saw to accurately cut long mitered corners. I’m completely disappointed.

I know other members have pointed out issues with this saw, but I had no idea it was this bad. My suspicion is that part of this is due to the fact that the miter adjustment assembly (the plate and the tooth) is plastic. It doesnt take much to simply push the saw out of square.

So Im wondering if I bought the wrong saw for doing finish carpentry. Anyone have any thoughts on this? A friend of mine told me I was nuts for buying a 12 inch miter saw for finish carpentry saying that a blade that big would cause issues. I have limited space and knew I’d want the capacity for cutting large crown so I thought 12 was a no brainer.

Any thoughts? Am I asking too much for the miter detents on my saw to line up perfectly each time I move them to a new position?


9 replies so far

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jonlan

43 posts in 720 days


#1 posted 11-11-2016 03:52 AM

Oh – and I forgot to add. It appears that the miter detents are not entirely accurate. When I get the square locked in perfectly at 90, then switch to 45 and make test cuts the miters are always slightly too steep to make a square mitered corner. A full set of test cuts on both ends of 4 pieces of woods (using the same locked in 45 degree setting on the saw) yield gapped miters. How can that be?

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DirtyMike

637 posts in 735 days


#2 posted 11-11-2016 04:12 AM

What exact blade do you have on the saw?

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jonlan

43 posts in 720 days


#3 posted 11-11-2016 04:17 AM

It’s a thin kerf blade. 100 count Freud. I’ve just realized that in some of my test cuts I was chopping rather than pushing so that accounted for some of the flexing I saw in the 45 degree cuts.

That however doesn’t account for the fact that when squared at 90, the 45 degree miters are significantly off. Is it possible that the detent block is just wrong? I can’t think of a way to adjust the detents for 45 without impacting 90 since they are all part of the same block. If you adjust anything the other detents move too.

Im wondering if Im just going to have to pick which detent I want to be right and then manually adjust the saw each time for other angles. That would be terribly frustrating though.

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DirtyMike

637 posts in 735 days


#4 posted 11-11-2016 04:37 AM

pushing huh? I have never tried that method with my sliding miter saw. I would contact Bosch about the correct alignment and tuning procedure before devoting anymore time. I have made things worse when trying to tune tools before and it is very frustrating.

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jonlan

43 posts in 720 days


#5 posted 11-11-2016 04:50 AM

When I push rather than chop I get a much straighter cut. When I was chopping I noticed that the cuts were coming out bowed in the middle.

Here’s a thought – is it maybe common not to use the miter detents for precise cuts? That is, Im wondering if it’s more common to manually set the angle with the detent override and just lock it in. If so, maybe that’s just how it is and I’ll need to find an accurate way to set the miter angle each time.

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Aj2

1171 posts in 1631 days


#6 posted 11-11-2016 05:10 AM

Well Jonian I have a Bosch glide saw.Ive had mine for least 5years.When I first got I did adjust the table to cut square. The blade your technique the material can affect accurate repeatable cuts.
And your square needs to be accurate to measure the saw and the cut.
I have a Forrest chop master full kerf when I want the best cut possible.
I’m sure you will figure it out but if your nearby maybe we can speed up the process.
I’m in So California

Aj

-- Aj

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jonlan

43 posts in 720 days


#7 posted 11-11-2016 05:44 AM

@Aj2 – Thanks, but unfortunately Im in MN :) Maybe you can hep me out because there’s a good chance that Im missing something. Here’s what I’ve done…

-I’ve checked the fences and found that they are inline with each other.
-I then loosened the 4 screws holding the detent plate in place, locked the saw in the 90 degree detent, and started making my test cuts and getting the saw closer and closer to perfect. During these cuts I use the screw in lock handle to lock the saw in position while making the cuts. Then I unscrew it to move it closer and repeat.
-Once I get the cut dead on at 90 I tighten up the 4 screws for the detent plate again.

At this point, my assumption is that the blade is 90 degrees to the fence. My thinking here is that if I have 90 degrees set correctly, and if the detent plate is accurate, then this is the only adjustment I should need to make in order for the other detents (45 for instance) to be accurate.

This is where things fall apart for me. 45 is slightly off despite 90 being dead on.

Is there something Im maybe missing here? I cant find a reason to adjust the fence at this point but is there a reason that I’d need to? I just can’t sort out how 90 can be dead on but 45 isnt.

Thanks

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JakeK

42 posts in 513 days


#8 posted 05-02-2017 03:50 PM

jonlan, i know this is a slightly old thread, but i’m wondering if you came up with any solutions. I am going through the exact same thing except i also noticed that my 2 fences arent perfectly coplanar. If you slide a workpiece along the left fence to the right, it will slightly bump into the right fence. I dont see any way you can adjust it. I did the same thing – squared it at 90 and then moved to the right 45. It was way off. I found that if you push it and hold it to the left side of the 45 detent and then lock it in, it is very close to 45 degrees, but that just sucks. BTW, when i did my 90 and 45 tests, i did it just using the left fence so it was consistent. Overall i’m pretty disappointed with this saw.

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jonlan

43 posts in 720 days


#9 posted 05-02-2017 06:19 PM

@jakek I ended up giving up on using the detents. My fences seem to be inline so Im not sure if we have the same issue but I finally just gave up on the detents for locking in angles. If I need perfect miter joints I do that on the table saw with a jig I built. The Miter saw is still handy for cuts that I cant do on the table saw and for quick work but its not a precision tool IMO. I too am disappointed with this but I just couldnt justify wasting any more time on it. If I need to do a precision angle on it I end up putting it in detent override and manually squaring it. A pain but it works.

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