Author Topic: How to straighten sides if all four are not square?  (Read 3111 times)

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Offline mikewaters

  • Posts: 15
How to straighten sides if all four are not square?
« on: October 04, 2017, 07:51 PM »
Hi everyone,

I have spent all day attempting to do this.
I have a piece of wood, all sides are off by at least 5 degrees.

Typically I would use my jointing jig for my table saw, but I need to learn how to do this using the TS75.
I have several woodpecker squares, nothing is square!

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Offline tjbnwi

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Re: How to straighten sides if all four are not square?
« Reply #1 on: October 04, 2017, 08:00 PM »
Explain your process and what tools you're doing this with.

Each edge should be square to the previous.

Tom

Offline SRSemenza

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Re: How to straighten sides if all four are not square?
« Reply #2 on: October 04, 2017, 08:10 PM »
Hi everyone,

I have spent all day attempting to do this.
I have a piece of wood, all sides are off by at least 5 degrees.

Typically I would use my jointing jig for my table saw, but I need to learn how to do this using the TS75.
I have several woodpecker squares, nothing is square!

Hi,

   Welcome to the forum!  [smile]

       It may also be helpful to know the dimensions of the piece you are working on in order to suggest which tools will be best suited?

Seth

Offline mikewaters

  • Posts: 15
Re: How to straighten sides if all four are not square?
« Reply #3 on: October 04, 2017, 08:41 PM »
Hi everyone and thanks,

I am using the TS75 along with appropriate guide rails.
MFT TOP along with qwas dogs and qwas track. (I did not use them for this issue though)

My main issue is with sheet goods. I am purchasing high quality sheet goods, but I have always trimmed 1/8" off each side to get rid of any dings or splinters.

I set everything up according to the user guide and made a few test cuts, paying extreme attention to detail. I am a very patient person as well, so I never was frustrated (which helps)

I push the saw in a nice even motion without extreme gripping etc.
my technique is not in question.

So I marked 1/8" in from all sides and made my cuts, making sure that the track was square with on side using my woodpecker gadgets (several different squares and edges)
I set in my track clamps on each side.
A separate 3/4" piece of ply was under for sacrifice reasons.

I measure from the bottom long side to the top and the right side was 47-7/8" ! perfect! Right on the money!
I measure the otherside, while still using my pecker T-Square and it is 47-1/8! ut oh!
I then made sure my blade was 90. it is
Splinter guard is fine.
Track was not bowed.
Similar measurements were on all four sides...

So now I have a large sheet of plywood that is all out of whack.
And I am ticked off because that means that the plywood was never straight. (i think)
Please help :(
« Last Edit: October 04, 2017, 08:45 PM by mikewaters »

Offline Bob D.

  • Posts: 716
Re: How to straighten sides if all four are not square?
« Reply #4 on: October 04, 2017, 09:20 PM »
I am not sure I understand the cutting and layout process you used.

When I read this it sounds like you laid out a mark 1/8" in from each
edge before you made your first cut, is that correct?

Was the piece checked for square before you laid out your cut lines?
-----
It's a table saw, do you know where your fingers are?

Offline tjbnwi

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Re: How to straighten sides if all four are not square?
« Reply #5 on: October 04, 2017, 09:33 PM »
Straight line one edge.

This is how I set the rail to straight line;




Once that edge is done use one of your WP squares to draw a line using the straight lined edge as the reference edge.

Set the rail on the line. it should be square to the first edge.

You can repeat this process using the previous edge to reference the square.

You should have a perfect square when done.

You can also use rise and run calculations to set the rail.

I recommend you get the TSO rail square (I test for TSO, do a search on FOG, read up on it and decided).

Tom

Offline harry_

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Re: How to straighten sides if all four are not square?
« Reply #6 on: October 04, 2017, 09:34 PM »
I am not sure I understand the cutting and layout process you used.

When I read this it sounds like you laid out a mark 1/8" in from each
edge before you made your first cut, is that correct?

Was the piece checked for square before you laid out your cut lines?

Ditto.

Once you have made your first cut, everything should be referenced from that cut, as it should now be "known straight". If this is the long edge, the most accurate way to check for straightness is with a long straightedge or a piece of string.
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Offline Bob D.

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Re: How to straighten sides if all four are not square?
« Reply #7 on: October 04, 2017, 09:39 PM »
I am not sure I understand the cutting and layout process you used.

When I read this it sounds like you laid out a mark 1/8" in from each
edge before you made your first cut, is that correct?

Was the piece checked for square before you laid out your cut lines?

Ditto.

Once you have made your first cut, everything should be referenced from that cut, as it should now be "known straight". If this is the long edge, the most accurate way to check for straightness is with a long straightedge or a piece of string.

Yes, that is where I was going but was looking for an explanation of how
he had made his cuts before suggested how I would have proceeded.
-----
It's a table saw, do you know where your fingers are?

Offline lwoirhaye

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Re: How to straighten sides if all four are not square?
« Reply #8 on: October 04, 2017, 09:41 PM »
Testimony would indicate the plywood was out of square.   In carpentry the old adage to measure twice and cut once avoids some mistakes.  I've made some dumb ones for sure.  The ol' brain seems to not always fire on all cylinders.

Generally however I work from one edge and rip subsequent edges to parallel with the first established edge.   Square cuts can also be made from the first edge.  Compound errors abound in squaring panels on table saws and with track saws.   What is good enough is all about tolerances. 

That said, never assume the edges of a board are parallel unless you've made them parallel yourself.

Offline mikewaters

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Re: How to straighten sides if all four are not square?
« Reply #9 on: October 04, 2017, 09:43 PM »
The plywood was not originally square (rather rectangle, haha)

So if I measure in from one side 1/8" and the other side 1/8", I am only pushing in the uneven edge straight.
That is the issue.
Tom, I saw your video before I even made an account actually lol! I tried that, but again, the ply wood was
47-1/8"
47-7/8"

The plywood was originally 3/4" shorter on the left side than the right.
I believe now the wood was 48" on one side and the other side was 47-1/4"


Offline Bob D.

  • Posts: 716
Re: How to straighten sides if all four are not square?
« Reply #10 on: October 04, 2017, 09:47 PM »
"That said, never assume the edges of a board are parallel unless you've made them parallel yourself."

Yes, this has caught me a couple times in the past, but I learned to verify. You eyes can play tricks on you
and sometimes what 'looks square' is in reality not square.
-----
It's a table saw, do you know where your fingers are?

Offline mikewaters

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Re: How to straighten sides if all four are not square?
« Reply #11 on: October 04, 2017, 09:47 PM »
And, yes, I'm a funny and didn't check first haha


So, now how do I fix it?

Offline eddomak

  • Posts: 279
Re: How to straighten sides if all four are not square?
« Reply #12 on: October 04, 2017, 09:49 PM »
Even if the original had square sides, I would still use the following procedure.

Assuming the rectangle had 4 sides (A, B, C, D) the long sides being A & C...

1) Rip straight edge on A (assuming a removal of a factory potentially non-straight edge)
2) Rip a parallel edge on C, referencing a set distance from edge A
3) Crosscut edge B, referencing 90 degrees from edge A
3) Crosscut edge C, referencing 90 degrees from edge A

If it gives you any reassurance, mark all the lines first, and measure the diagonals to ensure both diagonals are the same...

Hope this helps
« Last Edit: October 05, 2017, 02:27 AM by eddomak »

Offline mikewaters

  • Posts: 15
Re: How to straighten sides if all four are not square?
« Reply #13 on: October 04, 2017, 09:51 PM »
Edd, how do I insure my first rip is straight though???

Sorry if this is so amateur, I am SO used to my tablesaw and jigs!

Ahhhhhh!

Offline mikewaters

  • Posts: 15
Re: How to straighten sides if all four are not square?
« Reply #14 on: October 04, 2017, 09:52 PM »
Thank you by the way everyone!!

Offline mikewaters

  • Posts: 15
Re: How to straighten sides if all four are not square?
« Reply #15 on: October 04, 2017, 09:54 PM »
Even if the original had square sides, I would still use the following procedure.

Assuming the rectangle had 4 sides (A, B, C, D) the long sides being A & C...

1) Rip straight edge on A (assuming a removal of a factory potentially non-straight edge)
2) Rip a parallel edge on C, referencing a set distance from edge A
3) Crosscut edge B, referencing 90 degrees from edge A
3) Crosscut edge C, referencing 90 degrees from edge C

If it gives you any reassurance, mark all the lines first, and measure the diagonals to ensure both diagonals are the same...

Hope this helps


Yes!!! I can't believe I forgot to Mark diagonals. Ugh!

Offline harry_

  • Posts: 1160
Re: How to straighten sides if all four are not square?
« Reply #16 on: October 04, 2017, 09:59 PM »
Edd, how do I insure my first rip is straight though???

Sorry if this is so amateur, I am SO used to my tablesaw and jigs!

Ahhhhhh!

see my previous post.
Disclaimer: This post is for educational and entertainment purposes only. Any resemblance to real persons, living or dead is purely coincidental. Void where prohibited. Some assembly required. Batteries not included. Contents may settle during shipment. Use only as directed. No other warranty expressed or implied. This is not an offer to sell securities. May be too intense for some viewers. No user-serviceable parts inside. Subject to change without notice. One size fits all (very poorly).

Offline tjbnwi

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Re: How to straighten sides if all four are not square?
« Reply #17 on: October 04, 2017, 10:13 PM »
Edd, how do I insure my first rip is straight though???

Sorry if this is so amateur, I am SO used to my tablesaw and jigs!

Ahhhhhh!

You state in your first response your guide rail is straight. Running the saw on a straight rail will produce a straight cut.

This does not assure the uncut opposite edge is parallel to the cut edge or that the sides are square to the cut edge.

Tom

Offline mikewaters

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Re: How to straighten sides if all four are not square?
« Reply #18 on: October 04, 2017, 10:32 PM »
Tom,
When I wrote straight, I mean that both ends were touching 1/8" mark I made.
After that cut was made, and I cut the short sides using a woodpecker T-Square, the same measurements remained.

Offline tjbnwi

  • Posts: 5310
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Re: How to straighten sides if all four are not square?
« Reply #19 on: October 04, 2017, 11:15 PM »
Tom,
When I wrote straight, I mean that both ends were touching 1/8" mark I made.
After that cut was made, and I cut the short sides using a woodpecker T-Square, the same measurements remained.

Immaterial if the rail was touching the marks. Straight is straight, just a line without reference to any other edge. If you set your rail diagonally corner to corner, you still have a straight line/cut. Angle of the rail for the first cut means nothing.

Use the anti kick back stop to set the rail, no measuring.

Tom
« Last Edit: October 04, 2017, 11:18 PM by tjbnwi »

Offline morts10n

  • Posts: 178
Re: How to straighten sides if all four are not square?
« Reply #20 on: October 05, 2017, 12:17 AM »
Back in the day, carpenters would reference the "factory edge" as a starting point. After copious years of cutting, one learns that removing the factory edge is the most important step to getting straight and square panels. We must turn a questionably 4'x8' [or 49"x97" sheet] into an accurate panel.

Offline eddomak

  • Posts: 279
Re: How to straighten sides if all four are not square?
« Reply #21 on: October 05, 2017, 12:24 AM »
When I wrote straight, I mean that both ends were touching 1/8" mark I made.
Hi Mike,

When I read your 2nd post about the checks you had made of not having a bowed track etc I assumed you would therefore have a straight edge. However some (including myself, just this weekend) have been able to introduce some slight sideways bowing/deflection (especially on joined rails) from accidentally pushing sideways during the course of the cut. These days I not only make a mark at either end of any long cut, but also in the middle. One of the posts above suggests using a string as a means of checking, but I save myself the effort and use a laser line.  [big grin]

Anyway, if you follow those steps above it doesn't matter if the first cut actually introduced an angle that wasn't there before, as the remaining 3 cuts will fix it all up.

Offline Peter Parfitt

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Re: How to straighten sides if all four are not square?
« Reply #22 on: October 05, 2017, 04:00 AM »
If you are relying on the 20 mm holes of the MFT3 to be in a perfect 96 mm square centre to centre pattern then this may cause some of your error.

Festool make no claim (as far as I am aware) that the pattern of holes on the MFT3 is in any way accurate. I think we have assumed that as they are being produced in an industrial production process (and are CNC'd) that they should be spot on. I am sure that many MFT3 tops will be pretty good but this may not always be the case.

Also, the diameter of the holes in the MFT3 top can vary from one top to another. This has caused huge problems for bench dog manufacturers who have either had to work out the mean diameter across a selection of MFT tops or use tapers to account for the variation in sizes.

With any cutting station, be it an MFT3 or custom made top, that relies on bench dogs to position the wood and the guide rail, you need to perform a 4 (sometimes called 5) cut test to verify its accuracy.

Peter
« Last Edit: October 05, 2017, 06:49 AM by Peter Parfitt »

Offline kevinculle

  • Posts: 153
Re: How to straighten sides if all four are not square?
« Reply #23 on: October 05, 2017, 08:20 AM »
The advice as to technique above is fine, but if I found a factory sheet of plywood to be as far out of square as you indicate I would find a new supplier.  Like others have noted when working sheet goods it is always a good idea to process the piece such that all factory edges are replaced with clean square straight cuts.  But I have never seen a sheet of quality plywood out of square by more than a pittance...certainly not by 3/4"!!!  Imagine the roofing or floor deck you would end up with if you you used such sheets as received, you'd potentially have 1 1/2" gaps!

Offline Wooden Skye

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Re: How to straighten sides if all four are not square?
« Reply #24 on: October 05, 2017, 08:41 AM »
Are you clamping the rail?  Even though you say your technique is correct, you could be moving the rail unknowingly at the end of the cut, since you mention the second measurement is off and I assume that means end of cut.
Bryan

TS 55, (2) 1400 Guide Rails, 1900 Guide Rail, MFT/3, Domino DF 500, 2 domino systainers, ETS 150/3, RO 90, CT 26, (2) OF1400, RO 150. RTS 400, LR 32 set, PS300 jigsaw, 3 abrasive systainers, (2) sys toolbox, (2) sys mini, clamps and other accesories

Offline mikewaters

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Re: How to straighten sides if all four are not square?
« Reply #25 on: October 05, 2017, 12:21 PM »
Thank you gents.

Offline eddomak

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Re: How to straighten sides if all four are not square?
« Reply #26 on: October 05, 2017, 08:22 PM »
Thank you gents.
Awesome that you got the help you needed!  [smile]

If you're processing sheet goods a lot and want to make quick square cuts, you might want to look into the TSO Products Guide Rail Squares (GRS-16, & GRS-16PE). You can see a lot of YouTube reviews as well. I purchased one a couple of months ago and it seriously makes things so much faster than marking up both a start/end point (often the end point being out of reach and needing to walk around to the other side and back) lining up the rail to a square etc. I highly recommend this, and I am only a home hobbyist. I got the "PE" version where you can reference both off the near edge as well as the far edge, and have definitely referenced off the far edge.

Offline mikewaters

  • Posts: 15
Re: How to straighten sides if all four are not square?
« Reply #27 on: October 06, 2017, 09:54 AM »
Thank you gents.
Awesome that you got the help you needed!  [smile]

If you're processing sheet goods a lot and want to make quick square cuts, you might want to look into the TSO Products Guide Rail Squares (GRS-16, & GRS-16PE). You can see a lot of YouTube reviews as well. I purchased one a couple of months ago and it seriously makes things so much faster than marking up both a start/end point (often the end point being out of reach and needing to walk around to the other side and back) lining up the rail to a square etc. I highly recommend this, and I am only a home hobbyist. I got the "PE" version where you can reference both off the near edge as well as the far edge, and have definitely referenced off the far edge.

I actually have one. I had trouble make sure the rail was straight the entire way.

Offline Cheese

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Re: How to straighten sides if all four are not square?
« Reply #28 on: October 06, 2017, 10:00 AM »
Back in the day, carpenters would reference the "factory edge" as a starting point. After copious years of cutting, one learns that removing the factory edge is the most important step to getting straight and square panels.

Amen...

Mike, as others have said, I'd also seriously recommend purchasing the TSO GRS-16PE as it makes the squaring process so much easier. I purchased the GRS-16 because it was released first, however I find the PE version to be a lot more convenient to use.

Offline DynaGlide

  • Posts: 68
Re: How to straighten sides if all four are not square?
« Reply #29 on: October 06, 2017, 10:06 AM »
Back in the day, carpenters would reference the "factory edge" as a starting point. After copious years of cutting, one learns that removing the factory edge is the most important step to getting straight and square panels.

Amen...

Mike, as others have said, I'd also seriously recommend purchasing the TSO GRS-16PE as it makes the squaring process so much easier. I purchased the GRS-16 because it was released first, however I find the PE version to be a lot more convenient to use.

End of the day why would anyone buy the non PE version? Cost is similar. They try to sell both as a package but wouldn't it make more sense if you really wanted two to get the PE versions.