Are straight edges mythical??? - Woodworking Talk - Woodworkers Forum
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post #1 of 24 Old 11-07-2015, 11:47 AM Thread Starter
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Are straight edges mythical???

I am fuming at the moment. I have tried and tried and tried to get a straight edge on some rough cut walnut. I have watched video after video on how to get it. I've measured every angle on every saw that i can think to measure to ensure 90 degree angles. YET STILL, gaps of around 1/16th when I put the two boards together.

End goal is a walnut table top.

I tried the table saw jig where you attached the walnut to a straight board and you should come away with a straight edge.

I 've tried my 4" and 6" jointers. I don't care for the fences, even though they are 90 degrees in every spot i check, still no nice smooth edge.

I've tried a staight board clamped to the wood and running the circular saw down it. You guessed it - no straight edge when i put to boards together.

I'm attached 2 pictures. The first i wrote "GOOD" on the edges because they were the 2 boards I checked with my t square and everything seemed great. BUTTTTTT.....looking at the picture, you can see daylight on the other side.

Second pic, has 1 board that I cut and labeled "Good." Second board has an angle on the edge - BUT THE GAPS LOOKS BETTER THAN THE FIRST TWO BOARDS!?!?!?!?!?

Anyone have any suggestions. I'm at a loss. Thought I was doing pretty good, now I'm not sure what to do. Should I try to find someone locally that would square them up for me? Where does one find someone? I don't know. I'm open to anything right now. Including walnut firewood. Thanks.
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post #2 of 24 Old 11-07-2015, 11:58 AM
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Cutting a straight edge on a table saw should be routine. Unless your fence is somehow slipping.

You mentioned a jig. Does this mean that your rough cut wood does not have one side that is essentially straight?

Do you have a problem getting the fence on the jointer 90 degrees to the table? However, that does not seem to be the problem as the gap looks uniform.

Because no method you use seems to work I do not think it is an equipment problem. I think technique must be the gremlin.

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post #3 of 24 Old 11-07-2015, 12:17 PM
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I guess if all else fails, you could line up two pieces like pictured, use a straight piece for a guide, and run your circular saw through the boards where the gap is. That should produce a good joint.
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post #4 of 24 Old 11-07-2015, 01:45 PM
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Are you using a feather board on your table saw? I don't have on and should , but I use a helper with long boards on the back side to help insure the board stays against the fence.
Short pieces I've had no problem but the long ones I've noticed can walk away if your not careful, then you have a dip in the middle.
Maybe switch to some cheap pine until you get this figured out.
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post #5 of 24 Old 11-07-2015, 02:37 PM
where's my table saw?
 
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two reasons for "gaps'

First there is a curve in one or both of the boards when looking down from the top or along the edge.

Second, the edge is not square to the surface on one or both boards.

A table saw will replicate a slight curve on a ripped board unless you use a straight line rip jig. I get good results with the jig I made, good enough for gluing using clamps.
"Straight" is a relative term and in woodworking straight enough is often good enough. A variation of 1/32" is the most I would allow in a 4 ft board. You can clamp it well enough to eliminate that amount of variation.

You may be seeking perfection where it is not necessary.... I donno?

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #6 of 24 Old 11-07-2015, 02:55 PM
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Try running one board through the jointer with the face against the fence, and the next one with the back against the fence, then see how they match.

Alexis de Tocqueville was a very smart man.
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post #7 of 24 Old 11-07-2015, 03:28 PM
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You said you're using rough cut walnut. Is the face you run against the jointer fence or table saw flat? If you're using a jig, is it flat, and is the jig edge that runs against the fence straight? If so, then I'd also suspect operator error.
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post #8 of 24 Old 11-07-2015, 03:53 PM Thread Starter
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Thanks for the responses. I stepped away for a while to calm down.


Yes, I used a feather board on the table saw.

To flatten the face, (the boards were wider than my jointer), I put the boards on a flat board and attached them to the board. Then I put shims there there was an warping, and ran it thru my planer. I started working on the edges once the faces were smooth and straight.

So since this is going to be a table top. How much of a gap can I get away with an cover it up to where it isn't noticeable? I know the glue and saw dust trick, but I've never done it on a piece like a table top.
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post #9 of 24 Old 11-07-2015, 04:25 PM
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Hopefully you never use the glue and sawdust trick on a table top.

If all else fails clamp two boards side by side with a gap a bit less than your straight router bit, run the router down the gap against a straight edge making sure both edges are being cut. Even if the straight edge is not perfectly straight the two boards will fit together. Continue one board at a time until the top is glued up.

Wise men speak because they have something to say; fools because they have to say something -Plato

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post #10 of 24 Old 11-07-2015, 05:01 PM
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You might need to fine tune your jointer. If the blades are not good and sharp and the rear table not exactly level with the cutting edge of the knives it can drive you nuts trying to make a good joint.

If the jointer is set up right you can eliminate a gap in the middle by starting the cut in the middle of the board and turning it around starting the cut in the middle again using only the rear table. By doing this you are trimming wood off the ends of the board instead of the middle. If the gaps were on the ends of the joint you could start the board barely on the rear table trimming wood off the middle.
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post #11 of 24 Old 11-08-2015, 11:01 PM
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Quote:
Originally Posted by Steve Neul View Post
You might need to fine tune your jointer. If the blades are not good and sharp and the rear table not exactly level with the cutting edge of the knives it can drive you nuts trying to make a good joint.

If the jointer is set up right you can eliminate a gap in the middle by starting the cut in the middle of the board and turning it around starting the cut in the middle again using only the rear table. By doing this you are trimming wood off the ends of the board instead of the middle. If the gaps were on the ends of the joint you could start the board barely on the rear table trimming wood off the middle.
I can't imagine the jointer leaving a curve like that on the edge ...unless the board was bowed to begin with and you apply too much pressure on the infeed table which straightens the board out (making the knives cut along the whole length) and then after pressure is released it springs back into a bow. But since it cut along the whole edge, the bow is maintained.

Ask me how I know.
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post #12 of 24 Old 11-10-2015, 09:01 AM
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I suggest that you check the jointer set up.
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post #13 of 24 Old 11-10-2015, 09:16 AM
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If you're using a straight line ripping jig for the edges, be sure it fits perfectly (doesn't wobble) in the miter slot and it stays flat on the table.
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post #14 of 24 Old 11-10-2015, 05:49 PM
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The knives used to machine the wood in the first photograph were in bad shape,you can see lots of ridges.This alone will be a difficulty.A sharp set of knives and a carefully set up machine will help massively.

So would a sharp No7 plane.
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post #15 of 24 Old 11-10-2015, 06:14 PM
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In theory yes, but you can get two edges they fit together perfectly as far as the human eye can tell. A jointer can produce a better edge than a table saw, but a table saw can produce an edge far better than that.
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post #16 of 24 Old 11-10-2015, 08:18 PM
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I see several possible issues and some things that have nothing to do with the gap.....
1st ...90 deg has NOTHING to do with this issue...this is a straight line issue...90 deg only effects the flatness the boards are going to glue in the perpendicular/opposite plane.

2nd ...you didn't mention the length of the top....a 1/16 th is nothing for a glue line in 8 ft but is awful for a 18" length

3rd... HOW was this wood dried???? and is it straight grained or more wavy /knotty as one pic shows???
Drying too fast causes fatique in wood and when ripped it reacts with more warping and bowing....sometimes called casehardening.
If the wood is more knotty/ wavy grained than it's harder to keep the wood from moving as it's ripped. some older woodworkers were known to cut/rip oversize then thinly rip/joint to final specs to prevent the least movement flipping from side to side.

4th... the jointer is the best way BUT like all equipment it has limitations and varies in quality... the longer the bed the easier to be flatter/straighter. As other equipment it still needs precise set-up to do it's best job....IF the blades aren't sharp or the alignment correct it will crown or cup the desired straightline and cause this issue.

5th...did you dry the opposite edge/flip to see if it's just a bow/crown and it would work...that would tell you it's in the wood if one side is bowed in and the other bowed out.

6th... is it at the correct MC 7-9%

edit: reread post #8....your blades are DULL!!!! according to the face in one of the pics and you mentioned the wood is warped.

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Last edited by Tennessee Tim; 11-10-2015 at 08:28 PM.
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post #17 of 24 Old 11-10-2015, 08:52 PM
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hold on there partner....

The angle on the edge, whether it is 90 degrees or not, and of the mating edge has everything to do with whether there is a gap or not. You can NOT mate an 89 degree edge with a 90 degree edge and not have a gap on one side of the boards. This is why when jointing, you should rotate the next board end for end. This insures that any variation of the fence from 90 degrees with be accounted for...



Assuming lines AB and CD are parallel, angle AGH is equal to angle DHF whether they are at 90 degrees are not. A rip on the table saw would mate with another board IF the second board was flipped end for end, even IF the blade was not at 90 degrees. Hope I'm making this clear...?

To mate 2 boards without a gap and without flipping would require they both be exactly at 90 degrees.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 11-10-2015 at 09:16 PM.
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post #18 of 24 Old 11-10-2015, 09:44 PM
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The gap his pics show are caused from length tips or such touching...you can see all the way through. IF it were a degree issue they would touch let's say on the bottom and not the top edge if laying flat and you couldn't view/see through....kinda like a V exaggerated. This causes a completely different issue.

edit: I can take 2 boards with 87 deg angles that are true straightlined and lay them correctly and have a gap free and flat surface after glueing.

Have a Blessed and Prosperous day in Jesus's Awesome Love, Tim
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Last edited by Tennessee Tim; 11-10-2015 at 09:47 PM.
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post #19 of 24 Old 11-10-2015, 10:24 PM
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that's what I was sayin'

When you say "lay them correctly" that's exactly what I was trying to explain.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #20 of 24 Old 11-10-2015, 10:40 PM
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Quote:
Originally Posted by woodnthings View Post
When you say "lay them correctly" that's exactly what I was trying to explain.
I'm with you though.....true 90 degrees makes life MUCH simpler!!!!

Have a Blessed and Prosperous day in Jesus's Awesome Love, Tim
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