Miter saw acting weird (re-titled thread)

[museumguy]

i had the problem with my DW. pulled the fence off, gave it to my nephew (machinist) to take to work and see what his measuring machines showed.
it was .032 out from end to end of the fence. he took .040 off on whatever machine he used but now i have perfect miters using either side of the fence.

I've often wondered if this was a possible solution. Thank you for posting.

[rayknight]

If both sides of your fence are straight and your stock is straight and flat, I suspect technique based movement of the sawhead.
For truly precise jointery quality cuts most advise well constructed sled and table saw, and use miter saw for breakdown and less precision requiring cuts.
the sum of all the bearing tolerances (blade, pivots, sliders, etc) will allow visible movement, esp with sliders (try it with the saw off).  Most of us learn to live with it and cutting from the same side, intuitively learn to cut with no or minimal side load on the handle. (usually operating saw with dominant (i.e. right usually) hand.  cutting with opposite hands is always awkward and probably some side load introduced.

I agree with prior posters on checking fence for straightness with best straight edge available, blow out any dust or chips in bottom corner of fence, and make sure stock is straight and clamped or held to fence, but if all that is addressed, I would look at technique (but maybe you are ambidextrous) and ask why you need to cut from opposite side and avoid when possible and precision/accuracy needed.

[KingwoodFan1989]

No, I'm not ambidextrous...I just think it ought to be perfect on both sides, not just one. As for the person who said they gave the fence to a machinist, I'm not gonna do that. You shouldn't have to. It should be ground to within a few thousandths at worst before it gets put on the saw to begin with. To the one who said to throw away the tools I'm using to measure...what tools should I have? A machined straight edge and a machinist's square? What I have seems to work just fine.

I'm gonna try a few more tests today and report back later.

[Handplanesandmore]

 To the one who said to throw away the tools I'm using to measure...what tools should I have? A machined straight edge and a machinist's square? What I have seems to work just fine.

I don't think you need to throw away what you have (if someone has suggested that). Just check that they are within tolerance (yours, that is). Most woodworkers have more accurate tools for set-up or reference purposes.

If you are in the US, something like this is a good deal: https://www.harryepstein.com/index.php/1...r-usa.html

Straight edge: http://www.leevalley.com/us/wood/page.as...5313,50074 (Steel ones are more accurate but also more expensive.)

Those you have right now are tools for carpentry work, framing etc. Furniture demands more stringent machine and joinery set-ups.

Simon

[KingwoodFan1989]

Gotcha. I'll check those out in a bit. I figured out one thing I did wrong, though...the reason the tool that came with the saw had pieces chip off the male end was because the torx inserts on the fence bolts are one size bigger than that tool (maybe I should change the thread title to "I'm dumb" 
 ). I just got a second ratcheting screwdriver at Home Depot that came with a bunch of torx bits, and I got all the bolts loosened up. I also picked up a brand new framing square while I was there (a big one, too), so I'm gonna go see if I can get things into calibration.

Here's what I think might be happening: I was thinking about it last night after reading about it, and I found out that a bowed fence can be an issue. I think it might just be a few thousands bowed towards the parts of the fence that are closest to the blade. That would explain why it looks flat, but putting the blade square to one side while the other fence is tilted a bit in the opposite direction could definitely add up to a visible error. I'll try to see if I can fix it. Stay tuned!

EDIT:

Just as I thought, it is bowed....pics below. My straightedge is within a couple thousandths, and based on my feeler gauges I'd say the fence is between 7 and 9 thousandths out at the worst part. I guess all the errors do add up after all. Here's the thing...this is more than the fence was out by when it was on the saw...it is somewhat flexible (I could push the small bow out when it was laid on my jointer's outfeed table). I'm hoping this means I can force it into being perfectly (or darn close) symmetrical and the screws will hold it in place. I saw this blog post last night (http://dwaltsawz.blogspot.com/2011/10/de...html)...it was for the 718 model, but I'm assuming that used the 1 piece fence like the newest lines of DeWalt miter saws, right? I'll just see if I can use some clamps to hold it perfectly in place as I tighten the screws. I'll report back later or edit this post if nobody else posts before then.

ANOTHER EDIT:

*Sigh* No luck...You can make the fence flex, but when you go to screw the bolts in, that forces the fence back into the same position as was causing the issue in the first place. Very disappointing. I'm certainly gonna be calling DeWalt on Monday about this and getting to the bottom of it, because (mini-rant alert) any sliding miter saw over $300 should have a PERFECTLY even fence and be able to cut PERFECTLY square on BOTH sides. I shouldn't have to spend an outlandish amount of money for a miter saw (like with the Festool Kapex...almost $1500...you've got to be kidding me!) to get good enough results. Yes, you get what you pay for, but this isn't some cruddy Harbor Freight slider that cost less than $200, it's a DeWalt that cost $360 (normally $420-ish), so this should NOT EVER be an issue. What's most disappointing is how well everything else is working...it's super easy to square up the blade (at least on one side of the fence), it feels good to cut with it, the results are pretty consistent, it looks nice, etc...that's why I'm not giving up on this saw. (mini-rant over)

I feel like I'm a pretty unlucky person when it comes to buying new tools, as there always seems to be some slight but significant issue that comes on one included part that I have to re-order. Same thing happened with my Bosch sander ($220...kinda expensive for a ROS)...first friction ring wouldn't allow the sander to spin quickly enough on wet surfaces. The second one I got, after a break-in period, does it correctly. I certainly hope it only takes a single re-order to get a fence that works. My main concern is the shifting that occurs when screwing the bolts in...I assume that has to do with the machining of the holes (and countersinks that receive the angled undersides of the bolts). There could be two layers to the problem here, so I'm gonna be going into some major detail with DeWalt on the phone Monday. All 3 of my other DeWalt power tools have served me extremely well overall for around 10 years with minimal care...only significant issue I had was having to get the arbor replaced on my 10" table saw. That same saw is experiencing resistance when raising the blade (wheel won't turn, and when I force it, the mechanisms raising the blade kind of "pop" up into place) up until a certain height, but that saw is over 9 years old! I didn't expect this from a new saw (certainly not from this brand), and I WILL get this solved. The question is, are their standards for checking the trueness of the fence up to par with mine? And will the machining be correct on the holes so that the fence able to be perfectly square on both sides?

[Stwood_]

Yep. I was thinking about that today while out and about, that it was most likely a bent fence. Bent or the casting settled back some after machining.

I'd call Dewalt and ask for another fence. In the meantime, (if you keep the old fence) I would rasp out one side of those fence holes and push that fence into square.

[Handplanesandmore]

Since it is new, I suppose you can simply call Dewalt and ask for an exchange.

Not to suggest that you get a Kapex, but Festool will replace any lemon within 30 days (?). No need on the owner's part to try to fix anything like what you have gone through and shared.

Do bear in mind that the average miter saw is not a precision tool as such, and the tolerance level varies. If your replaced miter saw (knock wood) still does not perform as expected, consider building a zero clearance table which can be fine-tuned for true cuts on either side of the blade.

Simon

[KingwoodFan1989]

Funny how we come up with stuff all of a sudden like that, huh, Stwood?

And Simon, I think I'll go the route of a replacement fence. As I said earlier, I REALLY like everything about the saw other than this. The tool having pieces break off was my fault for not thinking about how it might only fit with certain screws but not others. Plus, it still actually works more than good enough for the screws it does fit, so I'm technically not at a loss with that tool. I just hope it's not also the holes that are in the main body of the saw that are off.

Also, I know what you mean about it not being a precision tool, but it's just a bit frustrating how perfect the results are when using one side of the fence but not while using the other one or both at the same time. I'm sure it's doable to get a fence that's not out of flat. If it's out by just a tiny bit and there is still a few thousandths of an inch out at the far end of the cut on the right side of the saw, that's more than good enough. But right now, it's probably around 1/16"-3/32" at the end of a cut that's not even 7 inches wide (with the saw having almost 10" of capacity at 0 degrees without any special setup). And when using the full fence, it throws both cuts off by probably half that, which is still out of my tolerances. Neither of those should be considered within tolerance for even a Harbor Freight saw let alone one of this caliber (standard price about $400-450). 

My opinion...I think if saws at this level are out on one side, it should be by significantly less than 1/64" across the full width of cut, not by 1/16" or greater. As the saws get higher in price, I think any saw that's off on one side should be out by no more more than about half that or, in the case of the Kapex, even down into just being a couple thousandths or less. And at the end, I feel these should be exceptional flukes, not something that is a regular occurrence. I feel like the rest of this weekend is gonna go by REALLY slow because their customer service doesn't open back up until Monday. Plus, with Christmas day being less than 2 weeks away, I hope they get a fence that is totally flat on and off the saw on the first try, because I'm sure shipping will take longer than normal given the time of year.

IF (and that's a big if) by some misfortune I can't get a fence that's totally flat, I'd probably look into another saw with split fences so they can be adjusted if they're not coplanar. You shouldn't have to rig up a zero clearance anything (other than a throat plate insert) on a saw like this. Maybe my expectations are a tad too high, but that's just how I feel. I hope and pray that I can get this fixed, because it's really the only issue I have with the saw.

[daddo]

That's pathetic to say the least. That fence should never have been allowed to be installed. This does not speak well for Dewalt at all. No quality control.
This is the reason I open the box at the store and check the tools before I buy.

The fence should be made in two pieces so you can adjust it.

[EdL]

One piece fences like that should be outlawed, the designers, drawn & quartered.

Went thru the same crap years ago with my old Milwaukee.

The casting warps, plain and simple. Nothing can be done to change that, its a poor design.

If it has 2 bolts per side, just cut the danm thing in half. Thats what I did.

Align one side square to the blade, then align the other side to the first side.

Ed