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Please help: DeWalt miter box table not coplanar?!?

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Forum topic by etc6849 posted 08-13-2012 02:30 PM 2274 views 0 times favorited 7 replies Add to Favorites Watch
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etc6849

14 posts in 1653 days


08-13-2012 02:30 PM

Topic tags/keywords: dewalt miter box coplanar

So, I finally put a level across by DeWalt miter box. I’ve attached a picture of the problem on my DW718 compound sliding miter box.

This is my saw here: http://www.amazon.com/DEWALT-DW718-12-Inch-Double-Bevel-Compound/dp/B000ASG8A8/ref=sr_1_8?ie=UTF8&qid=1344868115&sr=8-8&keywords=dewalt+dw718+sliding+miter+box

It appears the middle portion of the table is lower than the two coplanar ends. The middle portion rotates and rides on a PVC shim. I have barely used the saw, so this is a disappointment. I had planned on cutting mdf for the back of the fence as there are bolt holes for this. I can see it being very cumbersome to use mdf for the table top too as there are no bolt holes to attach the mdf and if I make two adjacent 45 degree cuts, the middle portion would fall out…?!?

Are all miter boxes this poor in quality? What should I do? Anybody have a similar issue?

I am concerned that when I cut material, it may not be cut at 90 degrees unless the piece stretches to the other side of the base that is coplanar. Further, even if a piece does reach both sides of the table, half way through the cut the issue seems to throw the angle off a tad due to the board flexing in the middle.

PS: I went to Lowes last night and several of the DeWalt saws have this issue. I would not recommend buying DeWalt anymore. I looked at a Chinese made Hitachi miter box and it was coplanar all the way across the top.

-- A free home automation program called Premise: http://www.cocoontech.com/wiki/Premise


7 replies so far

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Praki

197 posts in 3462 days


#1 posted 08-13-2012 04:07 PM

You might find this blog post interesting.

http://thecarpentryway.blogspot.com/2012/06/dewalt-de-fault-postscript.html

-- Praki, Aspiring Woodworker

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etc6849

14 posts in 1653 days


#2 posted 08-13-2012 04:32 PM

Thanks, I had read that blog post already. The Kapex looks like a great 10” saw and I might be interested, but I already bought a $120 12” full kerf blade for the DeWalt. The blade helped a lot as previously I could see the DeWalt blade deflect as I cut material.

I got suckered into one of the hot deals during the holidays on a miter saw and now I’m paying the price. I think a monkey could have designed a better saw.

Unless some folks on here have some ideas I think the next stop for the saw is craigslist. I’ve been thinking about trying the new older style Bosch 5312 (12” sliding dual bevel miter saw) or the non-sliding Bosch 4212.

I know the Bosch saws are probably made in China, but I’ve been happy with other Bosch stuff I’ve bought recently and not happy with any DeWalt stuff I’ve bought recently. I plan to buy it through home depots website so I can return it though if it’s crap.

-- A free home automation program called Premise: http://www.cocoontech.com/wiki/Premise

View Bertha's profile

Bertha

13003 posts in 2158 days


#3 posted 08-13-2012 04:38 PM

My DeWalt died but I didn’t use it all that much. I’ve been looking at the big Bosch but it’s pretty pricey and I heard at least one bad experience with it. We all know the Kapex is the best but it’s entirely impractical for me, a hobbiest.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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pintodeluxe

4858 posts in 2278 days


#4 posted 08-13-2012 04:40 PM

Does it produce cuts out of square? I have never put a straightedge across my Dewalt 12”, but it produces beautiful, square cuts.
Is there an adjustmant for this?

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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Bertha

13003 posts in 2158 days


#5 posted 08-13-2012 04:43 PM

It may be that your zero clearance (kind of) insert is peaked. It kind of looks like it in the picture. Pop it out and lay the level again.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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etc6849

14 posts in 1653 days


#6 posted 08-13-2012 04:50 PM

The level in the picture is flat on both ends of the base, just not on the middle rotating part. In an ideal world, you’d want everything to be coplanar. Since the two ends are coplanar, it’s just that the insert and rotating portion are too low. Yes, the insert is slightly higher, but it is still not coplanar with the two ends of the base…

I agree the cuts will be 90 degrees in one direction since the back fence is aligned and is coplanar, but vertically, the cuts could never be perfect, although I haven’t cut enough thick material to be sure. I’m going to cut some trim laid upright tonight and post some more pictures. I’ll cut from the left, then rotate to the right and measure the scrap with some calipers. I suspect the 1/16” gap will affect the results since a^2 +b^2 = c^2 and if you cut a short piece, it would lay on one end and on the middle portion and would be slightly tilted down at the insert.

-- A free home automation program called Premise: http://www.cocoontech.com/wiki/Premise

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etc6849

14 posts in 1653 days


#7 posted 08-13-2012 11:19 PM

So, here’s a diagram of the issue. I measured everything, and the gap was not as big as it looks! However, it will cause crown molding to never have great corners. See my math as follows:

For a 90 degree cut, the worst case error is .113 degrees (see diagram for math).

For a 45 degree bevel cut the math is similar, but I’m not going to bother doing it.

For a normal 45 degree miter cut, you would see the .226 degree error (.113×2) on the face of the joint in the plane perpendicular to the 45 degree cuts; assuming the material is laying flat and you are making a square frame.

So, if your material was 3/4” thick, your cut would be off .00148” from square (.00148” = tan(.11283 degrees)x.75”). Plenty acceptable for woodworking.

However, if you were cutting something taller, such as crown molding or trim laying vertically, for 3” tall material the cut is off by: tan(.11283 degrees) x 3” = .005908”. So for a corner, you would see approximately: 2 x tan(.11283 degrees) x 3” = .0118” which is may or may not be acceptable. This would show up as a gap at one end of a 45 degree inside corner.

As you can see, the error would increase linearly as the height of the work piece increases. If your work piece goes across the the rotating center (e.g. touches the two ends), your cut would still be affected due to the wood bending as it is being cut, but the error would not be as much.

PS: I used a dial indicator and a jig (UNA-GAUGE) to do the measurements so they are very accurate. I first zeroed the jig on a known flat surface. The dial indicator is accurate to .0005” and is not the PhaseII indicator that is accurate to only .001”.

-- A free home automation program called Premise: http://www.cocoontech.com/wiki/Premise

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