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Thread: Miter Saw Vertical Cuts not Square

  1. #1

    Miter Saw Vertical Cuts not Square

    Hello All,

    This is my first post so if I am not in the right area or not following the rules correctly please let me know. I did search the forum and I have one similar case to mine but it appears it that case, clamping the wood solved the problem. (This thread )

    I am having trouble getting square cuts out of my Hitachi C10FS sliding miter saw. I have had the saw for a few years and mostly use it for rough cuts. I have squared the blade up well and I get great cuts with the sliding function but when I perform a vertical plunge type cut they are always off. So far what I have done to try to fix it: Trued ,squared the fence, clamped the wood, put on a full kerf blade, changed my technique, cut very slowly. I took the saw apart some and after some careful examination with a combination square and calipers, it seems that the hinge pivot casting is not parallel to the blade spindle casting. I am assuming this is suppose to be parallel to each other? I emailed Hitachi and the closest repair shop is over 2 hours away, and I bought this saw used a couple years ago from a friend who didn't report anything wrong with it- so it's not under warranty.

    Is there any hope for this saw? I am hoping I could fix it because I hate to just throw it away but right now I am many hours invested in trying to fix it and by now could have bought a new one for the man hours I have put in.

    Thanks in advance for your help!
    Attached Images Attached Images

  2. #2
    Join Date
    Jun 2008
    So Cal
    Is that a Forrest chop master blade? Have you layed a reliable straight edge across the bed where the wood sits to see if it’s flat. Your small square is only showing you that 3 inches of bed is square to the blade.
    Every miter saw has its secrets to uncover
    Good Luck

  3. #3
    Join Date
    Mar 2006
    Blog Entries
    Being really generalized I would say that half of the CMS alignment issues come from the table/fence and the other half come from the blade support mechanism. If you confirm your table and fence or add a sacrificial table and fence to override any problems with the supplied one you can scratch that possibility off the list. If your cuts are still deviating from your desired result try to confirm that blade is not deflecting. Deflection is usually caused by poor path control which places lateral pressure on the spinning blade. At the basic level you are after two planes of control; flat material support with perpendicular blade travel. The availability for deviation from this on a CMS or SCMS is reported on $150 saws and $1500 saws.
    Take me to the hotel - Baggage gone, oh well . . .

  4. #4
    Join Date
    Jul 2007
    NE OH
    Have you tried just ignoring the square, and adjusting the bevel stop until you get a square cut on the work piece? Of course that may throw off the alignment when sliding...

    Any way to shim the casting you think is out of alignment? At least check to see if there are any burrs or flashing preventing the castings from mating properly.

    If you have a digital angle gauge, it would perhaps be instructive to zero it on the table, then attach it to the blade and see what the angle does as you plunge the saw.
    --Certainty is the refuge of a small mind--

  5. #5
    Join Date
    Sep 2003
    Gold Coast, Australia
    Just to clarify- if you cut a board laying flat on the saw using the sliding function, and inspect carefully, do you see the same bevel on the cut?

  6. #6
    Your only options are to; 1.) have a machine shop machine your hinge pivot casting and blade spindle casting parallel. Or 2.) Order an OMGA and be done with it. You could try to find a way to shim it, or just live with it. Every miter saw on the market has some degree of inaccuracy. The only ones that are perfect are manufactures like OMGA and CTD.

    Even the much touted Festool Kapex is not going to be anywhere close to an OMGA or CTD. The Kapex is not much better if any at all than that the Dewalt DW780 when it comes to accuracy. What you get with the Kapex is ease of bevel setup and somewhat better dust collection. That’s it.

    I will say that if you go with option #1 in having a machine shop machine the hinge pivot casting and the blade spindle casting parallel, you would then have a dead nuts accurate miter saw.

  7. #7
    Join Date
    Nov 2021
    Columbia MO and Howard County MO
    I don't see many images of your saw on the web and I can not see the detail in your images. It is hard for me to imagine that this is not an adjustment issue. Check out part 102, "Set Pin" It may be bent or not properly engaged. I would consider the set pin to be a general reference and do the final squaring up with a square.

    Hitachi C10Fs 10" Slide Compound Miter Saw | Model Schematic Parts Diagram —

    Screen Shot 2022-05-21 at 7.16.29 AM.png
    Last edited by Maurice Mcmurry; 05-21-2022 at 9:26 AM. Reason: image
    Best Regards, Maurice

  8. #8
    Join Date
    Nov 2006
    N.E. Ohio
    A sliding compound miter saw isn't a radial arm saw even on it's best day - any more than a .357 magnum is close to a .35 Remington.

    I do have to add this edit though.
    I had a couple of low end SCMSs - a Workforce from HD that required nearly constant adjustment - but - once adjusted it worked fin for a while.
    The big problem with it was - you didn't know when it was going to go out.

    I think that's the issue.
    Top shelf sliders stay in adjustment longer - but - eventually they all go out of whack.
    How easily they can be adjusted & how long they hold is what's key.
    Last edited by Rich Engelhardt; 05-21-2022 at 9:14 AM.
    My granddad always said, :As one door closes, another opens".
    Wonderful man, terrible cabinet maker...

  9. #9
    It appears from your photos that the blade is square to the table, or at least that part of the table. Yet when you make a cut in that same position, the cut appears significantly out of square. Is this what you’re experiencing?

    If this is what’s happening, it appears there is deflection somewhere when the blade is engaged in the wood, or the workpiece is moving. If you lay that same board down flat against the table and tight against the fence so that you’re only cutting 3/4” of material, pull the saw head fully out and push the saw through the cut, does the vertical cut come out square?

    If the saw head is pivoting squarely to the table under no load conditions & not square when actually cutting, I think I would be looking for the deflection point as opposed to a manufacturing defect. Could be a wear part, something that needs adjustment, dull blade, poor seating of the blade on the arbor flanges…

  10. #10
    Join Date
    Nov 2021
    Columbia MO and Howard County MO
    I just tinkered with my De Walt. My set pin has a few degrees of slop either side of 90 degrees. I have to set it to 90 with a square. then tighten.
    Best Regards, Maurice

  11. #11
    Join Date
    Jun 2008
    So Cal
    What’s the deal with blade is that a tablesaw blade. Too many unanswered questions. I think we got a question from a drive by. He’s gone gone like the whiskey.

  12. #12
    Thanks for all the replies, did not expect to get so many! Not a drive by I have been putting up shelves and painting, but I will reply soon with some more follow up and measurements... I think the saw is toast

  13. #13
    Join Date
    Mar 2019
    Los Angeles, California
    I have that exact saw and liked it so much, I had it re-built. This is what I do to align it from scratch.

    1. Start with a new blade, and check the blade for flatness. Don't install it yet

    2. Ignore the right side of the fence for now, indeed, you could pull it back so nothing touches it.

    3. Extend the saw all the way out and lock it

    4. Using a framing square, adjust the fence so it is square to the saw flat side, where the blade seated.

    5. Tighten the fence, not to a final tightness, but snug

    6. Put your blade on the saw and check for square along the whole axis of the saws slide, square when collapsed, square when fully extended. It should be close. Don't sweat it if its off by a 16th at this point.

    7. Adjust the left fence so the blade tracks square along the whole axis of the swing. Re-clamp the fence

    8. Get yourself some test boards, the best are 10" wide, 1/2 thick plywood.

    9. Make a test cut, and adjust the fence angle in or out to dial in a perfect cut. This may take a dozen attempts.

    10. Once you have a perfect cut, install the right side of the fence in line with left, using a straight edge.

    11. I often follow up with more test cuts using mdf or a hardwood.

    The key to this method is step numbers 4 and 7.

    Because this saw extends on those large tubes, the saw will extend and collapse in a straight line. One simply adjusts the left fence to be square with that axis.

    Do all this and report back.
    Last edited by Thomas McCurnin; 05-21-2022 at 3:01 PM.


  14. #14
    Okay, here is some more info. I bought this saw used from friend of mine (who painted it a puke green!) , who I bet only used it for rough cuts because he had a really nice table saw, so I don't think he ever noticed it was off (I trust him).

    I used a sacrificial board as the base to make sure my table isn't off. I took the left side of the saw of (the non-motor side) and then used my 12in combo square (a new blemish square from tay tools) to square it as precisely as possible to the table using the whole blade diameter. I kept the original fence since I made sure that was square in several spots. I replaced the blade from a thin kerf Forrest woodworker II blade to a framing 40t spyder blade with a full kerf (only full kerf I could find at the box store). I made sure to go really really slow to make sure it is not deflecting. -No dice.

    I also tried to just square the saw to my cuts instead of to the table which then made the sliding cuts off (I checked the rails, straight as can be). When I get eye level with the blade, on my plunge cut, I can see that it does not track vertically.

    When I do a sliding cut from front to back (how I always do them) then my cuts are practically square.
    I thought about shimming the hinge somehow but I am not sure how to do that really?

    Bobby- My first thought was to grind down the metal where the spindle housing sits, but then I don't think that the spindle would sit correctly in the saw as it would sit too deep? And, I have no idea what that would cost.

    Maurice- I did notice that the set pin is bent, but to remedy this, I just used a sharpie and mark an arrow so I can set it the same way every time.

    I have spent probably no joke, over 10 hours or more trying to get this thing square (.

    Attached is the exploded view of the hinge that I used to check the spindle housing, which it seems that the spindle housing is off by as much as a 1/16th, (I think even more but I would have to take it back apart again)-just from one side of the oval housing to the other. The way I check this was using my combo square edge and then clamping my calipers to it and checking the depth on multiple points of the housing.

    Thanks for all your help and thoughts everyone!


  15. #15
    Thomas- Thanks for the thoughts, that is about how I how I set it up . I've got a precise straight edge to get the fence correct and then used my square to get the slide I would say perfect, (have some 8in boards) I can get great square cuts when I am using the slider, but if I do a plunge cut, it shows that it is very off. If I slide in to a piece placed vertically against the fence, it is better than if I plunge it, but still off, it seems that the saw does not track correctly on the vertical axis.



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