How to straighten sides if all four are not square?

[mikewaters]

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!

 

[tjbnwi]

Explain your process and what tools you're doing this with.

Each edge should be square to the previous.

Tom

 

[semenza]

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

 

[mikewaters]

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

 

[Bob D.]

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?

 

[tjbnwi]

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

 

[harry_]

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.

 

[Bob D.]

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.

 

[lwoirhaye]

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.

 

[mikewaters]

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"

 

[Bob D.]

"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.

 

[mikewaters]

And, yes, I'm a funny and didn't check first haha

So, now how do I fix it?

 

[eddomak]

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

 

[mikewaters]

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!

 

[mikewaters]

Thank you by the way everyone!!

 

[mikewaters]

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!

 

[harry_]

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.

 

[tjbnwi]

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

 

[mikewaters]

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.

 

[tjbnwi]

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