Can't get a straight edge..AHH - Woodworking Talk - Woodworkers Forum
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post #1 of 30 Old 12-16-2015, 08:21 PM Thread Starter
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Can't get a straight edge..AHH

I'm a woodworker from a former life -- haven't really done any fine woodworking since high school but picked up a table saw and want to start doing it as a hobby.

I don't have a jointer and have seen videos where people use a jig to get a straight edge on a board. I tried building a similar jig but am having some trouble.

after i run it through the saw, i put a level to it. the back half of the board is straight as can be, but about half way down you can start seeing some light under the level. by the end theres a little more light -- we're talking maybe 1/32". I've run several boards with the same result.

I'm keeping my jig against the fence as far as I can tell. Is there something I can look for in my saw setup or technique in running long boards (56") that might cause the front of my board to be a little shallow?

I assume 1/32" will give me some issue in edge glue up -- if that is the case, and im unable to get the table to make a straight enough cut, do you think a small hand plane will work to get it close enough for gluing? I don't have a larger #7 or 8 plane and haven't really picked up a plane in decades. Could use some ideas or advice from some people with experience.
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post #2 of 30 Old 12-16-2015, 08:57 PM
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Perhaps there is something wrong with the saw but more than likely the blade is too dull for that kind of work. A blade that is a little dull can bend while making the cut.
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post #3 of 30 Old 12-16-2015, 09:03 PM
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I'm very new to woodworking and tackled some large red oak countertops recently. I used the same method to get the edges prepped for glue up and had some areas that weren't 100% tight. To my eye they appeared to be about 1/32 as we'll.

I talked it over with my dad(long time hobby woodworker) and he assured me the gaps would not be a problem. So far so good with the tops and they have been in place for ~6 months.

May not be the 100% correct answer but it worked ok for me.
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post #4 of 30 Old 12-16-2015, 09:54 PM
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I would check the alignment of the saw first. .005 misalignment of the fence was giving me trouble on my saw. If that doesn't fix it try adding a feather board. If that doesn't fix it I would buy a good quality blade.
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post #5 of 30 Old 12-17-2015, 05:54 AM
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Is the level straight? If youre using a non-straight reference edge, well, yeah, your cut wont be straight. Try cutting 2 boards using your jig, then butt the cuts against each other. Check for gap that way, just to rule out the level being the problem

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post #6 of 30 Old 12-17-2015, 06:46 AM
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Quote:
Originally Posted by hwebb99 View Post
I would check the alignment of the saw first. .005 misalignment of the fence was giving me trouble on my saw. If that doesn't fix it try adding a feather board. If that doesn't fix it I would buy a good quality blade.
99 44/100 per cent of wood workers could not measure 00.005. And that small of an error would not matter in woodworking even if they could measure it.

How can you use a feather board on that type of jig?

George
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post #7 of 30 Old 12-17-2015, 08:03 AM
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Quote:
Originally Posted by epicfail48 View Post
Is the level straight? If youre using a non-straight reference edge, well, yeah, your cut wont be straight. Try cutting 2 boards using your jig, then butt the cuts against each other. Check for gap that way, just to rule out the level being the problem
Yeah, levels are not the best indicator of a straight edge. Flip it around when measuring to rule it out.

Also I can't see how a table saw can cut a straight edge for half a cut and not on the second half...unless the blade starts to wobble or something. The cut would be off by a certain amount in a linear fashion along the length of the cut. E.g. every inch you would be off by say 5 thou...
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post #8 of 30 Old 12-17-2015, 09:06 AM
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an 48" aluminum level is a good test

That's what I use for a straight edge when setting up my jointers. It's about the most precision tool you can buy for a modest amount, around $30.00 or so AND you will use it for other tasks.

You did not say how long your pieces are OR how long your level is, OR what it's made from... wood or metal?
You fence should look like this with a 1/16" to 1/8" offset behind the blade from a scrap of Formica or other thin material:


You do need a very sharp blade for this and you must feed slowly to avoid bending the blade. A full kerf blade is the best for this operation and it need not be a full 10" diameter. A stiff blade like from a dado set will work.


As to technique, when ever you joint a board, you must sight down it before jointing. If it has a concave curve, you should "joint/plane" in from both ends to reduce the curve as much as possible, just like you would do if you were planing by hand. This is important and few instruction manuals mention it. After there is very little curve left, run it through your setup and check it with a straight edge or aluminum level. Do the same with the next board and then match them together to check for gaps/daylight between them.

If all the above are taken into account, you should have as good a mating surface as possible....

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; 12-17-2015 at 10:01 AM.
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post #9 of 30 Old 12-17-2015, 10:48 AM
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Quote:
Originally Posted by GeorgeC
99 44/100 per cent of wood workers could not measure 00.005. And that small of an error would not matter in woodworking even if they could measure it. How can you use a feather board on that type of jig? George
It does make a difference. Set your fence .005 tighter at the back then the front and see how that works out for you. I adjusted it where the front of the blade is .002 closer to the fence then the back with much better results.
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post #10 of 30 Old 12-17-2015, 12:50 PM
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Quote:
Originally Posted by hwebb99 View Post
It does make a difference. Set your fence .005 tighter at the back then the front and see how that works out for you. I adjusted it where the front of the blade is .002 closer to the fence then the back with much better results.
5 thousands of an inch is the thickness of a sheet of writing paper, on most saws once the fence is moved it will not likely even remain at that same tolerance, any improvement using a dial gauge to set up a saw is purely physiological.

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post #11 of 30 Old 12-17-2015, 02:09 PM
where's my table saw?
 
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My pencil lines are wider than .005 "

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 #12 of 30 Old 12-17-2015, 02:31 PM Thread Starter
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I checked out my saw this AM and found that the fence is not running parallel to my blade. Hoping this may be causing the issue.

Could it also be that I'm using boards that are slightly bowed? The jig definitely holds the bow down pretty well while cutting, but I'm trying to figure anything else that could attribute to the issue. I need to get these ready for glue in the next 48 hours.

If I'm unable to get them straight enough with my saw, I'm gonna have to look at other options. I've got a small rusty old hand-me-down hand plane -- will that get the job done or do i need a #7 or #8 plane to really get it straight? any other ideas that won't cost much?
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post #13 of 30 Old 12-17-2015, 02:36 PM Thread Starter
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matt, im curious if the clamps closed up your gaps or if you mean there are small gaps but the glue holds ok.

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Originally Posted by mattshake9451 View Post
I'm very new to woodworking and tackled some large red oak countertops recently. I used the same method to get the edges prepped for glue up and had some areas that weren't 100% tight. To my eye they appeared to be about 1/32 as we'll.

I talked it over with my dad(long time hobby woodworker) and he assured me the gaps would not be a problem. So far so good with the tops and they have been in place for ~6 months.

May not be the 100% correct answer but it worked ok for me.
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post #14 of 30 Old 12-17-2015, 02:50 PM
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Yeah the gaps closed up with moderate clamp pressure. I used tightbond 2 for the glue up and all seems well for now. In the 3 separate top pieces I was good for 1 gap per glue up. It seemed to me that the gaps happened within a few inches of the end of the board. I believe it happened at the start of the cut not the end. Possibly being at a very small angle to the fence when starting out. The shortest pieces were about 5 foot long and the longest pieces about 8, so control was difficult at the start. 2 inch thick oak is heavy.
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post #15 of 30 Old 12-17-2015, 03:40 PM
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did you read post no. 8?

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Originally Posted by flamingoezz View Post
. I need to get these ready for glue in the next 48 hours.

If I'm unable to get them straight enough with my saw, I'm gonna have to look at other options. I've got a small rusty old hand-me-down hand plane -- will that get the job done or do i need a #7 or #8 plane to really get it straight? any other ideas that won't cost much?
Just get your setup and technique down correctly.

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 #16 of 30 Old 12-18-2015, 07:03 AM
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Quote:
Originally Posted by flamingoezz View Post
I checked out my saw this AM and found that the fence is not running parallel to my blade. Hoping this may be causing the issue.

Could it also be that I'm using boards that are slightly bowed? The jig definitely holds the bow down pretty well while cutting, but I'm trying to figure anything else that could attribute to the issue. I need to get these ready for glue in the next 48 hours.

If I'm unable to get them straight enough with my saw, I'm gonna have to look at other options. I've got a small rusty old hand-me-down hand plane -- will that get the job done or do i need a #7 or #8 plane to really get it straight? any other ideas that won't cost much?
"I checked out my saw this AM and found that the fence is not running parallel to my blade. Hoping this may be causing the issue."

Will not cause this issue but causes other problems.

I think you stated your real problem in a later post when you said you may not have the material solid against the fence at the start.

George
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post #17 of 30 Old 12-18-2015, 10:00 AM
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Quote:
Originally Posted by mattshake9451 View Post
Yeah the gaps closed up with moderate clamp pressure. I used tightbond 2 for the glue up and all seems well for now. In the 3 separate top pieces I was good for 1 gap per glue up. It seemed to me that the gaps happened within a few inches of the end of the board. I believe it happened at the start of the cut not the end. Possibly being at a very small angle to the fence when starting out. The shortest pieces were about 5 foot long and the longest pieces about 8, so control was difficult at the start. 2 inch thick oak is heavy.
You should have tool stands at both ends of your saw if the material is to heavy to manage properly. You can buy them, or build something yourself to do the job, lots of ideas out there.

Clamps are meant to hold two fitted boards together until the glue dries, forcing gaps closed usually results in other problems.

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post #18 of 30 Old 12-18-2015, 10:32 AM
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there is an exception ....

Quote:
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Clamps are meant to hold two fitted boards together until the glue dries, forcing gaps closed usually results in other problems.
There is a technique that relies on a gap between the boards. It's called a "spring joint" and is used when edge joining boards. I've never used it, but it requires lowering the outfeed table on the jointer to create a slight concavity on the edge. This article explains it:
http://www.finewoodworking.com/item/...ps-best-friend

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 #19 of 30 Old 12-18-2015, 10:55 AM
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Doing it intentionally is an entirely different situation, and the gap is not at the ends. Sometimes a little knowledge is a dangerous thing.

“Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.”
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post #20 of 30 Old 12-18-2015, 03:32 PM
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If I remember you said that this gap was consistent. If these boards are being glued as you cut one lay it down, cut the next and flip end to end so the grain pattern reverses on the ends which should be done to keep the finished board from warping any way. So if the gap was consistent this flipping should remove that gap. Lots of good advice. This type of problem is best solved on location as you are the only one seeing the solution possibilities.
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