perplexing situation

[4fingers]

Ok -- I'm not some newbie sawdust maker without experience. I've built many pieces of furniture over the years but this has me baffled -- at least tonight. I'm building a bed. the foot baord has 5 slat between the top and bottom rail - out side are ~3" wide, the next 2 are ~4.5" wide and the middle one is ~8" wide. The inside distance between the top and bottom rails is ~ 9". Morstices in the rails were laid and cut at the same time as well as the tenons for the slats. The rails are the same length using the "finger test" when they're laid on top of each other. So far so good I thought. When I put it together for the 1st time to see where the tenons into the post should go I couldn't get the rail ends to line up. If I squared one side the top rail was ~3/16 shorter than the bottom rail. I know it sounds crazy I checked and rechecked. All the edges are square, the slats are the same length. It's almost like the bottom rail edge is concave but it's straight. what am I missing -- sanity -- common sense? both??

[Larry Jaques]

Borrow a 24" dial or electronic caliper. I'll bet that either your mortises are offset or your slat lengths (or tenon centering) are off.

-- In the depth of winter, I finally learned that within me there lay an invincible summer. -- Albert Camus

[Joe]

(This is on the first cup of coffee - bear with me.)

3/16 over the width of a bed (single?, queen?, king?) isn't much - a slight error either way could be additive. Say you have a parallelogram from the slightest non-square cut - 1/32 of an inch, but it's consistent on every board. That will pass the finger test on long boards as you line them up one way ( /___/ ). But you are really out a 16th (1/32 + 1/32). Other end of the board is the same way. Edges and center measurements are all identical, and so is corner to corner. Now flip a board ( \___\ ). Measures the same way - good. But now compared to each other, you have - /___/ and \___\ , where you have doubled the error - as compared to each other. This assumes 1/32 on same width boards - you have different widths so the difference would likely vary. Now if you were also a 32nd shy on one and over a 32nd on another...

a 6' board didn't shift until I got to the other end to check. Then I'd flip a board at a time, re-clamp and check to see if I could spot the difference. Or it could be the phase of the moon.

-J

[tiredofspam]

Could you have copied your motise locations to the wrong side, instead of making a mirror, you repeated the same mortises? So now you have a parallelogram instead of a square.

How about some pics.. might help seeing it.

[Doug Miller]

4fingers wrote in news:XnsA098DC3EDBF8Aasdasdasdasdasdasdas@69.16.185.250:

I suspect that your "square" isn't.

[Dave]

On Mon, 23 Jul 2012 11:34:05 +0000 (UTC), Doug Miller

You're probably right. One of those things that with just the slightest variance, increasingly skews every measurement that follows.

[Larry Blanchard]

One possible fix would be to narrow the bottom edges of the slats a little so you'd have some adjustment room. I say the bottom edge because the resulting small gaps would be covered by the mattress and box springs.