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I own a Hitachi C10FCE2 10-inch miter saw, it is my first miter saw. I'm a woodworking beginner but learning fast. I recently installed a "Makita A-93681 10-Inch 80 Tooth Micro Polished Mitersaw Blade" to replace the pretty crappy blade it came with.

I just noticed today while cutting some 3/4" cherry for a box that the miter saw isn't cutting a flat edge, even though the edge seems to be square. I've calibrated all of my tools to an obsessive degree. I have several accurate engineer's squares, double squares and combo squares that all agree with each other, and they (plus a digital angle gauge) all agree that the miter saw blade is perfectly perpendicular to the back fence and the floor. I didn't really expect a discrepancy, so I hadn't been meticulously checking the resulting wood. Thus, I don't actually know whether this problem has always been here, or if it appeared some time down the line. I only bought it a few months ago, and the blade just a few weeks ago.

The "problem" I speak of is not that the cuts are off square in the traditional sense. A try square doesn't show significant deviation from square. However, when I place the two halves of a fresh-cut bit of wood together, they don't line up smoothly along the entire surface. There's sort of a gap there that is most prominent on one side. There's also some blade marks that are deeper than they should be, so much so that I can feel some parts of the end grain are a few thous higher than others.

I switched to my crosscut sled after noticing the problem and my ends are nice and square and flat again. Does anyone know what this is, if it can be fixed or if I need to dump the saw and/or the blade? Is it my technique, machine setup/calibration, a hardware fault or something else like I messed up installing the blade? If the blade is the culprit, I might still be in the return window for Amazon. If I had a shooting board I'd probably just clean up my ends, but until then I depend on a clean cut right off the saw.

FYI, all parts of the saw are tight with no play/wiggle where there shouldn't be. My technique is to push the wood against the back fence and down on the widest part of the saw bed, clamp the wood down, spin the saw up to speed, slowly drop the saw through the wood while applying light pressure down and back to keep it square, stop when it reaches bottom, wait for it to stop, then lift it.

I took some pictures of the gap and also the end grain, though the saw marks probably don't even show up in the pics. enter image description here enter image description here

Man I've spent way too many words describing this.

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    Don't worry about the long description, that's perfect for diagnosing something like this (our usual problem is too little information to go on). I thought this was down to blade vibration/resonance, but your further description of it working when using the crosscut sled led me to discard that. Re. shooting the cuts, that's a good thing to be thinking of, I won't say many but some pros would routinely plane to perfect certain cuts, particularly if the sawn face is a show surface. Anyway hopefully someone with more experience of power saws will be along to help diagnose the issue for you, – Graphus Oct 10 '16 at 7:29
  • If you have a high precision displacement guage, test to see if the saw wobbles. – ratchet freak Oct 10 '16 at 10:05
  • Confirm the insert is flush with the rest of the table so the workpiece isn't rocking slightly. Also let the blade come to a full stop before raising it. – rob Oct 10 '16 at 14:31
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    I tested with a dial gauge, both blades. Both exhibited identical behavior. About half to 3/4 of the blade's circumference was at 0, but the rest of the blade pressed the dial gauge inward (to the left) about 4-5 thousands of an inch. I did test cuts with both blades and they exhibited identical behavior - a flat cut toward the rear half and the front eighth of the saw and a visible gap in that middle section.. Since both blades are showing identical behavior, I guess the problem is with the saw. – JupiterJesus Oct 11 '16 at 18:05
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    Miter saws have a reputation of not being well suited for fine work. A lot of people call them "chop saws" for this reason. I imagine the problem with your saw still well exceeds the required tolerances for framing and carpentry. Still, I empathize with your frustration. – Charlie Kilian Oct 13 '16 at 17:02
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Based on your last comment, return the saw. This is not something you're likely to be able to fix easily.

This is a decent saw that usually cuts much better than this, you should feel comfortable exchanging for another one of the same model, this sounds like a freak one-off defect.

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    I came to this conclusion myself and your answer and other peoples' comments sealed the deal. It is too late to return it to Amazon, and if Hitachi doesn't honor the warranty (it should be a year) or expected me to pay shipping (which would be near the cost of replacing the saw, I think), I'll either sell it on CL to someone less demanding than I am, or use it as a rough cut saw to be followed by hand planing. I just built a shooting board and I'm learning to use it. If I need quality right off the machine, I'll use the miter gauge until I pick up another miter saw down the line. – JupiterJesus Oct 14 '16 at 5:12
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    @JupiterJesus Shame about not being able to return it to Amazon but glad you got your answer. If you need help on anything related to shooting (or the plane/planes) don't hesitate to ask a fresh Question or two. – Graphus Oct 14 '16 at 6:27
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You're expecting too much from a $120 saw and $35 thin kerf blade. Power tools in this price range just aren't manufactured to ultra-tight tolerances because there is a point of diminishing returns for the manufacturer, and they start cutting corners in some places in order to hit a certain price point.

You can try cleaning your arbor or replacing the washers on either side of the blade with higher-quality ones. You may be able to tell if the washers are not flat, or if one or both is inconsistent in thickness from one side to the other.

If you're getting 4-5 thousandths of an inch runout (slightly more than the diameter of a human hair) along some parts of your blade, that means mating 2 cut pieces may give you a gap as wide as 1/100 inch. Most people wouldn't pay attention to a gap this size when looking at installed crown molding from 4+ feet away, but even so, carpentry projects inherently have some amount of slop because time is money, and a skilled carpenter will have plenty of techniques for working around and hiding imperfections where it matters.

On top of that, whatever you measure with the blade in a static state most likely will differ when the blade is spinning at 5000 RPM, especially with a thin kerf blade whose plate will be less resistant to flexing than a full-kerf blade. Based on your experimentation, it seems this is not the major factor since the original blade produces the same results.

Considering the workarounds, you don't need to buy a $400 shooting plane; you can just as well use a $30 hand plane and shooting board, or clean up the edges with your crosscut sled.

That said, there is no reason to throw out your miter saw. At some point you may want to crosscut a very long board, which will be awkward on a table saw and may require you to move your table saw or rearrange your shop to accommodate the operation.

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