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"X" leg table question

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Forum topic by bignastyweather posted 04-26-2014 04:25 AM 897 views 0 times favorited 21 replies Add to Favorites Watch
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bignastyweather

4 posts in 240 days


04-26-2014 04:25 AM

Topic tags/keywords: question

Hello everyone, brand new to the forum here…and a novice woodworker.

I have a question regarding an “X” leg table design.
I’ve done some Google searching on this forum and found two relevant posts.
http://lumberjocks.com/topics/21435
http://lumberjocks.com/topics/27506

However I didn’t see a response (admittedly I just skimmed the posts) that answered my question.

My question is this…how do I calculate the miter angle cuts necessary to make this design work, given the following measurements/data?
- Legs are made of 4”x6” posts.
- Total width inside of the apron (right term?) is 30.5”.
- Height from floor to base/underside of table top is 30”.

And let me say this, I’m looking for math related answers here. I don’t have any cardboard or spare wood to draw up a template. I’d rather have a formula anyways b/c I can solve that quickly for any future projects I might do with this type of design. Does that make any sense? And sorry if I’m not using the right terminology or leaving out pertinent details here.

Thanks in advance!


21 replies so far

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Rick M.

4491 posts in 1128 days


#1 posted 04-26-2014 05:44 AM

If you can’t type, “how to calculate the angles of a triangle” into Google then I hold little hope you will make heads or tails of sines and cosines.

edit: less smarmy answer—Google “solve SSS triangle” or “law of cosines”

-- http://thewoodknack.blogspot.com/

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bignastyweather

4 posts in 240 days


#2 posted 04-26-2014 11:58 AM

Rick,
Despite the potentially simple-minded-sounding question, I am well versed in solving for angles in a triangle. You couldn’t have known this in advance, but I did take 3 calculus classes, plus differential equations, in college.
Perhaps I could have stated my question a little better, and explained that I’m pretty sure I have the answer already…but was looking for reassurance from others via explanations of how THEY solved this issue.

To your response about the “SSS triangle”...that won’t work. I only know 1 side for sure. The others, the hypotenuse (length of 4×6 edge between miter cuts) and the base (distance between inside edge of apron on one side and inside edge of mitered 4×6 on the other) depend on the angle I cut on the 4×6 post.

Got any other helpful tips?

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freddy1962

909 posts in 297 days


#3 posted 04-26-2014 12:38 PM

bignasty, I apologize for the way you were treated above. I can’t help you, maybe someone else can. Good luck with your project.

-- JEFF Illinois (Banks of the Mississippi)

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distrbd

1305 posts in 1194 days


#4 posted 04-26-2014 12:51 PM

B&N weather,the only helpful tip I could give you is to keep it simple,you could draw the the actual “X”leg on paper to the angle that you like the best , measure the angle using a protractor,transfer that measurement on a couple of scrap pieces of wood,cut,dry fit,adjust for a tight fit.it,s not complicated if you don’t over think it.

-- Ken from Ontario

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Buckethead

1946 posts in 617 days


#5 posted 04-26-2014 12:56 PM

There are extra considerations in wood working. Wood dimensions, for instance. In theoretical geometry/trig, one works on lines and planes. Two dimensions. A 2×4, for instance, has 3 dimensions, and does not represent a line. You need to account for thickness.

All in all, you say you have 30” in width, and 30.5 ” in height. That sounds remarkably close to being a 45 degree angle. (Assuming the legs extend to the outer dimension of the table top, and intersect at their mid point.)

Are we doing a picnic table?

But many a math challenged person can get this without math. No jig required.

Create the rectangle you mention. (30×30.5) on a sheet of ply, or on a floor, paper or whatever. (Just draw it) place a board (the lumber you’re going to use for your legs) diagonally. I would allow the board to center on the corners, forming at right angle top and bottom of the leg, meeting at the center of the board width) then place another board on top, intersecting to the other diagonal. Use some scrap of the same thickness to support near the ends. Now scribe both sides of the edge at the intersection, and at the outer perimeter of the rectangle. If you want to know what that angle is, measure it with a speed square or protractor. Do a couple spots to verify accuracy. The top and bottom angles, should be complimentary (= 90 degrees) to the intersection angles.

This method helps eliminate mistakes from overlooking various factors, and gives a visual of what you’re doing. Speaking of visuals…
Here’s the basic concept, though I did not draw a rectangle.


This is what I mean about cutting the legs at a right angle. The pencil mark roughly represents a 90 degree angle within the board. If you cut a full angle parallel to the floor, it leaves the end grain at a point, which is much more likely to be chipped off when sliding the table.

-- Bucket, any person that spends 10k on a bicycle is guaranteed to be a $@I almost started to like you. -bhog

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kdc68

2071 posts in 1025 days


#6 posted 04-26-2014 01:04 PM

+1 Buckethead….sometimes the best math is no math at all

-- Measure "at least" twice and cut once

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bondogaposis

2749 posts in 1099 days


#7 posted 04-26-2014 01:18 PM

Draw it in full dimension on a piece of paper. If you can’t draw it you can’t saw it. Then you can transfer the the correct angle to your sliding bevel gauge to set the table saw miter gauge.

-- Bondo Gaposis

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Buckethead

1946 posts in 617 days


#8 posted 04-26-2014 01:32 PM

Yes to drawing, but remember… You need to account for the width of the board. On this X, the long point of the top, will be the short point of the bottom. Changing the width dimension of the theoretical rectangle by the rate of the cut dimension. (And subsequently changing the angle) Work from the center of the board? Same problem… Rate of the cut is unknown. (“Rate of cut” is the length of the cut edge of the board) Far easier to simply lay it out beforehand. Literally less than five minute’s work.

-- Bucket, any person that spends 10k on a bicycle is guaranteed to be a $@I almost started to like you. -bhog

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theoldfart

4737 posts in 1199 days


#9 posted 04-26-2014 02:21 PM

^+1 to BH’s method, did the same thing for my bedside table. Drew out a full size template on 1/4 ply and took all my angles from that

Set my mitre box angles and depth stops

Angled half laps

BTW did not have a pic of the half lap on the drawing so I’m showing the angled tenon at the end.

-- "Aged flatus, I heard that some one has already blown out your mortise." THE Surgeon ……………………………………. Kevin

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EPJartisan

1093 posts in 1873 days


#10 posted 04-26-2014 02:37 PM

yeah i cant elaborate much on what has been said already… but on a side note … ergonomically, if you are interested. the top of your table should be designed to a maximum of 30” tall. to suit most chairs and match the average human scale. one inch may not sound like much.. but it make a huge difference in comfort. just a suggestion.

-- " 'Truth' is like a beautiful flower, unique to each plant and to the season it blossoms ... 'Fact' is the root and leaf, allowing the plant grow and bloom again."

View Buckethead's profile

Buckethead

1946 posts in 617 days


#11 posted 04-26-2014 02:39 PM

Kevin… Your joinery is immaculate. Your scholarly approach is paying off.

-- Bucket, any person that spends 10k on a bicycle is guaranteed to be a $@I almost started to like you. -bhog

View bignastyweather's profile

bignastyweather

4 posts in 240 days


#12 posted 04-26-2014 06:46 PM

Thanks for the help everyone. Turns out my mathematical approach was indeed correct. However, there were a couple of really helpful tips/visuals presented here. I’ll have to stash those away for the next project.

Thanks for the feedback once again. I’m looking forward to utilizing this forum for future projects.

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bignastyweather

4 posts in 240 days


#13 posted 04-26-2014 06:49 PM

Also…EPJartisan…thanks for pointing that out. I did make that measurement wrong; I measured to the underside of the table and, since I started with 2×8’s (planed to about 1.25”) I do probably need to shave a little off the legs to bring that back down.

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EPJartisan

1093 posts in 1873 days


#14 posted 04-26-2014 08:30 PM

Glad i could help. A bad measurement at the beginning gets really frustrating later. :)
A few years ago I made my first table base for my mother-in-laws and had to match to existing chairs, I also have the benefit of having a Industrial Design background and I loved ergonomics. So I grabbed my handy “Measurements of Man” book. Welcome to LumberJocks!

-- " 'Truth' is like a beautiful flower, unique to each plant and to the season it blossoms ... 'Fact' is the root and leaf, allowing the plant grow and bloom again."

View Rick M.'s profile

Rick M.

4491 posts in 1128 days


#15 posted 04-27-2014 02:10 AM

Got any other helpful tips?

Yes, skip the math because it’s excessively complicated and doesn’t necessarily solve your problem. If you end up with a weird angle like 51.4 degrees, it can be tricky to nail that exactly with a saw. I’ve built one X leg table and never picked up a calculator, pencil, or paper. I made the X (the legs) the width I wanted, used a straightedge to mark the angles, then a bevel gauge to transfer them to my saw. No math and it doesn’t matter if it’s a weird angle.

-- http://thewoodknack.blogspot.com/

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