Miter Saw Vertical Cuts not Square

[Matt Sotelo]

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 (https://sawmillcreek.org/showthread.php?78261-Help-my-miter-saw-won-t-cut-straight!))

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!

[Andrew Hughes]

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

[glenn bradley]

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.

[Paul F Franklin]

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.

[Greg Quenneville]

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?

[Bobby Robbinett]

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.

[Maurice Mcmurry]

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 — Toolbarn.com (https://www.toolbarn.com/blogs/parts-schematics/hitachi-c10fs-10-slide-compound-miter-saw)

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[Rich Engelhardt]

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.

[Eric Schmid]

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…

[Maurice Mcmurry]

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.

[Andrew Hughes]

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.

[Matt Sotelo]

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:(

[Thomas McCurnin]

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.

[Matt Sotelo]

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!


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[Matt Sotelo]

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.

Thanks,

Matt

[Edward Weber]

Checking the alignment as in the photo only shows where the blade ends up after the cut has been made. Unfortunately, it would seem that the blade isn't tracking at a perfect 90 degrees, only ending up there..
It almost seems as if something is twisted or as you mentioned " that the hinge pivot casting is not parallel to the blade spindle casting." to account for the cuts you're getting.
Sometimes you just get a lemon, if it can't be adjusted to the point where it cuts reliably, I would have to let it go and stop chasing a problem that can't be fixed.

[Thomas McCurnin]

Still very confused. Place one side of a framing square along the left fence on one side; and use the other side of the framing square against the sliding blade. Slide the saw back and forth against the square. It is either square or not square along the whole axis as you slide the blade back and forth.

So is it square as you slide the saw back and forth the whole 11 inches?

[Matt Sotelo]

Checking the alignment as in the photo only shows where the blade ends up after the cut has been made. Unfortunately, it would seem that the blade isn't tracking at a perfect 90 degrees, only ending up there..
It almost seems as if something is twisted or as you mentioned " that the hinge pivot casting is not parallel to the blade spindle casting." to account for the cuts you're getting.
Sometimes you just get a lemon, if it can't be adjusted to the point where it cuts reliably, I would have to let it go and stop chasing a problem that can't be fixed.

I think this is the case, it is not tracking at a perfect 90 degrees, only ends up there, and when I check it with a longer combination square, it doesn't end up square at the down position. I think this may be why I get some burning in my cuts because it doesn't track at 90 degrees but follows an angle.

Thomas- When I square the blade to the fence (from side to side) it is square. The problem is it is not square vertically and follows an angle as it lowers.

Sounds like I may have to give it up :(

[Lee Schierer]

I think this is the case, it is not tracking at a perfect 90 degrees, only ends up there, and when I check it with a longer combination square, it doesn't end up square at the down position. I think this may be why I get some burning in my cuts because it doesn't track at 90 degrees but follows an angle.

Thomas- When I square the blade to the fence (from side to side) it is square. The problem is it is not square vertically and follows an angle as it lowers.

Sounds like I may have to give it up :(

Has it ever been dropped or fallen over? I would guess the hinge pin that allows it to swing down is bent.

[Thomas McCurnin]

I think this is the case, it is not tracking at a perfect 90 degrees, only ends up there, and when I check it with a longer combination square, it doesn't end up square at the down position. I think this may be why I get some burning in my cuts because it doesn't track at 90 degrees but follows an angle.

Thomas- When I square the blade to the fence (from side to side) it is square. The problem is it is not square vertically and follows an angle as it lowers.

Sounds like I may have to give it up :(

Got it. At this point, it is not a matter of adjustment, the saw is buggered. I would either sell it for parts or send to an authorized service center who can properly diagnose the defective part and replace it.

[Bobby Robbinett]

If that is the old style of Hitachi with the rails in the back and not the front, that is a very well respected saw. If it were me, I would take it to a machine shop and have them machine the castings correctly to fix it once and for all. I would most definitely not attempt it yourself. So don’t go at it with a grinder or anything else. Take it to get done precisely and accurately so that when you get it back you will have the best miter saw on the planet not named OMGA or CTD.

[Dennis Jarchow]

I have a Hitachi c10FSH. It has been a very good saw with some limitations like the limited height to cut baseboard standing up. I had some issues with mine not always cutting square despite spending hours with squares and dial indicators. Turns out the bearings/bushings that surround the sliding rods had gotten loose. There is an adjustment at the back of the casting that holds the sliding tubes. I am not sure if that could be contributing to your problem, but it is worth checking.

[Matt Sotelo]

Lee- I myself have never dropped it but I was wondering about this, when I took out the pin, it looks straight as an arrow when put against an edge and rolled. It also fits nicely into the hinge area.

Bobby- This is I believe the gen I C10FS saw, with the rails in the back. From what else I had seen online I thought it was a pretty darn good saw, but if a saw doesn't cut straight, is it really a good saw ha? I am leaning towards taking it in to a shop to machine it right, only hiccup is if it is machined down more around the motor housing area (where I would assume it would have to be?) then I am wondering if the spindle would not sit in the housing correctly because it would be too tight. Although maybe the hinge could be machined to match the housing, and then just a shim used to take up the space? Just spit balling my thoughts here.

Dennis- I had thought about this and took it apart and adjusted the bushing tightness so there is no play, but I don't think that is the problem because when I slide it all the way back and lock the slide, it still does it, so I think the rails are eliminated from the problem, unless I am mistaken.

It sounds like my next step is to take it to a hitachi repair shop or machine shop. I am truly grateful for the numerous responses!

-Matt

[Matt Sotelo]

Pictures of the saw:

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[Andrew Hughes]

Is that a miter saw blade? The teeth look like they have a lot of hook the blade will self feed it has forward rake or hook

[Matt Sotelo]

Is that a miter saw blade? The teeth look like they have a lot of hook the blade will self feed it has forward rake or hook

It's just a cheap spyder brand blade, the only full kerf blade I could find, framing blade, 40t, 18 degree hook. I know it's not an ideal blade, just tried it for the full kerf to see about any deflection. I could try a higher tooth, low degree blade if you think that would help?

[Andrew Hughes]

It’s good practice to have the right blade for the intended use. I use the Forrest chop master and I’ve also used Amana tools blades. All full 1/8. If I were cutting MDF crown molding I would use the that blade you have. Then throw in the trash when I was done.
For cutting solid woods sharp wins every time.
Good Luck