I am totally lost as to how this could happen and need help figuring it out

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Forum topic by ohtimberwolf posted 04-08-2018 01:19 AM 11176 views 0 times favorited 30 replies Add to Favorites Watch
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984 posts in 3123 days

04-08-2018 01:19 AM

Topic tags/keywords: square 5 cut sled

Here is what is driving me bananas.

I built a sled according to the 5 cut method. I thought it was ok and I set it aside and did other things. After that, I took a wood rectangle ¼” thick that checked perfectly square and made a cut on each side of it with the sled. I then checked it again for square.

Now, after cutting all four sides and it being checked with the two metal squares and the draftman’s plastic square that I have, (the same ones I used to check the rectangle before cutting it,) the wood rectangle I cut measures as follows.

Side 1 ends up 17 ¾ inches.
Side 2 ends up 12 1/16 inches
Side 3 ends up 17 31/32 inches EDITED CORRECT SIZE
Side 4 ends up 12”

Here is what confuses me.
Side 4 is square to side 1
Side one is square to side 2
Side 2 is square to side 3 …but
Side 3 is off 1/16” to side 4 How can this be?

I have re-cut these 4 sides 3 times over again and the same problem exists. I use the same 3 squares as with the original piece that I started with before cutting it. I am simply baffled as to how this can happen.
Maybe I need to sleep on this and see what you guys say come Sunday morning.


-- Just a barn cat, now gone to cat heaven.

30 replies so far

View woodbutcherbynight's profile


6069 posts in 3179 days

#1 posted 04-08-2018 01:25 AM

How did you attach the runners to your sled? Someone else here once had issues and only used two screws for each runner. Way to easy to get bumped and be off.

-- Live to tell the stories, they sound better that way.

View TheFridge's profile


10859 posts in 2257 days

#2 posted 04-08-2018 01:29 AM

On the 5th cut you measure the width at top and bottom of the piece. It’ll give you the cumulative error over the linear distance you cut.

So pretty much .0625 difference over 59”. Way too much for my liking.

If the measurement of the cut off is bigger at the bottom the angle is greater than 90degrees from the side of the sled you cut from. If it’s smaller at the bottom. The angle is smaller than 90.

I used William Ngs video on YouTube.

Edit: it’s off pretty much .001 an inch on your sled.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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8906 posts in 3347 days

#3 posted 04-08-2018 01:30 AM

What are the diagonal measurements ?

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10477 posts in 4418 days

#4 posted 04-08-2018 01:59 AM

Did you rotate the part clockwise or counter-
clockwise for each new cut?

If it was counter-clockwise, you won the booby
prize. I won the prize myself recently as I hadn’t
done the procedure in a long time and decided
to wing it.

View TheFridge's profile


10859 posts in 2257 days

#5 posted 04-08-2018 03:02 AM

Just put the freshly cut side against the fence.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View clin's profile


1113 posts in 1767 days

#6 posted 04-08-2018 05:38 AM

You can’t have three corners square, and the forth not square if the sides are straight cuts. So there is either error in how you’re checking for squareness, or the sides are not straight.

Assuming the sled is square, are you being careful to make sure the wood is not moving along the fence as you make cuts. It actually pretty easy to impart some side force and push or pull a piece when try to hold it. I found I was doing this when I built my first sled. There is a bit of technique to using a sled. Only holding the wood back into the fence while making a cut.

If the sled is not square, you should still end up with the same angle on each corner, if you cut and rotate it in the same direction after each cut. Fresh cut to the fence as TheFridhe pointed out. So your problem cannot just be that the sled is not square.

-- Clin

View RandyinFlorida's profile


257 posts in 2838 days

#7 posted 04-08-2018 11:56 AM

check your squares. One or more isn’t square. If you aren’t familiar with checking a square Youtube it. It’s simple to do. Never assume a square is “square” till you have confirmed it.

-- Randy in Crestview Florida, Wood Rocks!

View MC's profile


234 posts in 3118 days

#8 posted 04-08-2018 12:02 PM

The error in your cut is multiplied by four on the last corner. Pick one side to use as your reference. Cut the two adjacent sides keeping the reference side against the fence of your sled. For the opposing side of the reference, use the table saw fence to make a parallel cut.

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56 posts in 900 days

#9 posted 04-08-2018 12:30 PM

run out on the table saw arbor?

View Mike_D_S's profile


605 posts in 2985 days

#10 posted 04-08-2018 12:56 PM

One of the guys above mentioned it also, but I would go ahead and check the sled again with the five cut method so make sure something isn’t out of whack.

The simplest answer is that with of a properly squared sled and using proper technique you shouldn’t end up with a rectangle that far out of whack. So I would go back to the beginning and recheck the sled using the five cut method.


-- No honey, that's not new, I've had that forever......

View WyattCo's profile


93 posts in 875 days

#11 posted 04-08-2018 01:23 PM

What is the sled constructed of? How are the runners attached? What was the final calculated setting when first constructed?

View bonesbr549's profile


1588 posts in 3838 days

#12 posted 04-08-2018 01:50 PM

Take a picture of your sled setup. Looks like slop somewhere. Also, if that was not a typo, your long side is 9/16” off? something is way outta whack. Second, to cut to length do you have a stop block mechanism, or are you just hitting a pencil line.

-- Sooner or later Liberals run out of other people's money.

View torus's profile


450 posts in 1184 days

#13 posted 04-08-2018 01:50 PM

Geometry rules:

1) The sum of the four angles is 360 degrees ( we are assuming the sides are strait)
2) If the angles are square (90 degrees) – the opposite sides should be equal.

Therefore your measurements are incorrect and most likely it is your square…

-- "It's getting better..." - put this on my RIP stone!

View tmasondarnell's profile


130 posts in 2560 days

#14 posted 04-08-2018 01:52 PM

In additional to all of the above, I will may the simple recommendation of checking to make sure you do not have saw dust other materials compressed on the fence—I have gone to the zoo on that one many times…...

View ohtimberwolf's profile


984 posts in 3123 days

#15 posted 04-08-2018 02:20 PM

1 Runners were attached with screws.
2 That is the video I used.
3 21 3/8×21 3/16
4 Clockwise.
5 I did that.
6 Could be but 3 are square every time. My biggest delema.
7 The squares are square. When flipped they all are straight up the same line.
8 I will have to think about what you are saying.
9 Arbor is true.
10 I believe that is what I am going to have to do.
11 I didn’t keep those figures.
12 Pictures taken and now posted.
13 Couldn’t agree more.
14 I did that but will do it again.

My sled made out of scraps.

Thanks guys. larry

-- Just a barn cat, now gone to cat heaven.

showing 1 through 15 of 30 replies

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