How to create square panels?

[10digit]

I apologize if this has been covered before, but here is my question:

How do you get accurate square panels?  I am cutting plywood down to make some shop cabinets and although the accuracy for this project isn't a must, I am using it to improve my skills.  No matter how hard I try, I am unable to get a panel that has either matching dimensions or matching diagonal measurements.  I have tried a roofing square, a sheetrock 48" square, and one of those adjustable plastic angle finders and still no luck.  I recall seeing a method of stiking two arcs to get a more accurate measure point than can be achieved from a square but cannot locate the article.  I think what I am creating is a slight parallelogram.  The long edges of the plywood are parallel, the short edges measure the same, but the panel is slightly racked.  I cannot get a good first 90 degree corner to work from and then the whole panel is thrown off from there.  HELP!!!

 

[BarryL]

Fingers

There is more than one way to do it...but spme that will guarentee results.  One of the first question anybody here will want to know before they can answer your question is "what do you have to work with"?  Are you working with festool stuff....together with a table saw.....do you have an equipped shop?  Let me know what you are working with and I will try to guide you.

 

[mwhafner]

I assume that you are using the TS55 that you show in your tag-line?

I use the FS-KS and have great results, after a little modification.  I used JB-Weld to lock it a 90 degrees.  A framing square also works well.  The FS-KS just locks into the rail and is a little easier to square.

Also, check to make sure that your stock is truly square to begin with.  Most of the sheets that i have bought at the box stores are not square.  I only use them for shop fixtures and jigs, but it is still a hassle to deal with.

I have also started using Woodpecker's Story Sticks for laying out my cuts from a parallel edge.  They are excellent.

 

[JayStPeter]

mwhafner hit on my first thought, which is to get accurate diagonals you must first start with parallel cuts.  If you're out of parallel to start with, square will never come.  There are a number of jigs and techniques that members here have come up with to ensure parallel cuts, then to ensure square cuts.

Here's a thread that talks about parallel cuts, including my jigs:
http://festoolownersgroup.com/index.php?topic=475.0

Here's a thread on how I make very square cuts:
http://festoolownersgroup.com/index.php?topic=2674.0

By using these methods, my accuracy is consistently less than 1/32" delta between diagonals on cabinet size panels.  I'm sure others will chime in with their methods and jigs that are equally accurate.

 

[JeromeM]

Fingers

There is more than one way to do it...but spme that will guarentee results.  One of the first question anybody here will want to know before they can answer your question is "what do you have to work with"?  Are you working with festool stuff....together with a table saw.....do you have an equipped shop?  Let me know what you are working with and I will try to guide you.

I also have the same problem. Parallel cuts are easy Square is not.

I was using a TS_55 and rail + usual tapes.

But may be as I have just got the  MFS 700 that may be the answer in the short term.

I will find out in about 2 weeks.

However other methods will be useful to know.

 

[10digit]

These panels started out as 4X8 sheets which Home Depot ripped to 2X8 to ease handling.  At home I used my TS55 and (2) 55 inch guide rails to trim them to 23 1/2 inches  They appear to be parallel along the long edges.  I then took my roofing square to verify the factory short edge was 90 degrees to the long edge and it seems to be.  I measured 30" from the short end and layed out my cut.  Lined up one saw guide and made the cut.  Checked the diagonals and they are not equal.

At this point I have to question the accuracy of my roofing square, my technique, and my TS55/guide rail combination's accuracy.  I've used the a square + b square= c square method and it proves I am not square.  I do not have an MFT so I must rely on some other method to establish a 90 degree corner from which I can work off of.

I do have a pretty good table saw and fence which I could use to make sure I have parallel sides.  But that doesn't help getting a 90 degree adjacent side.  I don't know if a speed square would be accurate over a distance of 20-48 inches.  What other methods do you recommend to get it dead on?

 

[sw1211]

If you get two sides parallel, use a cross cut sled or something similar on your TS to get it square.  Assuming your blade is parallel to the miter slot and the sled is set up correctly.

 

[Dave Ronyak]

Here's another thread containing many ideas how to align MFT fence and Guide Rail to get square cuts.  Square MFT.  My personal favorite is to use a large reference square to set the MFT fence square to the Guide Rail.  I use an 18 inch precision carpenter's triangle from Woodpeckers.   This same tool can also be used to lay a pencil line where you intend to cross cut and thus to confirm alignment of your planned cross cut before it is made.  In this photo, the precision triangle is the gold colored item which I am using to confirm that the DeWalt T-square accessory is ninety degrees to my Guide Rail.  

.

To get parallel strips that you will later cross cut into shorter lengths, there are also many ideas on FOG.  I prefer use of stops or a story stick.  Jerry Works manual on uses of a Festool MFS shows how to make and use such stops for accurate, repeatable parallel cuts.  I made a much less expensive version.

To use these shop-made stops, first lay the Guide Rail on the sheet to be cut and rip a straight edge.  Then make a pair of pencil marks at the desired strip cut width using a shop rule or tape measure.  Then set the Guide Rail with its splinter strip on the pencil marks.  Then set both shop-made stops to the required width setting, with both stops being placed on the Guide Rail next to each other.  Then relocate one of the preset stops adjacent to the other end of the Guide Rail, reset the Guide Rail, and make the rip cut.  You can now rip as many pieces as you need using your preset stops and all will have parallel sides and be of identical width.

Note that many roofing or framing squares are not square.  They may be close from the factory, but not precisely square.  You can check any square to determine if it is truly square by using it to draw a pencil line that is presumably perpendicular to your reference (base) edge with the handle of the square extending to your left, then flipping the square 180 degrees so its handle is extending to your right and drawing another line on top of or very close to the first line you drew.  If the lines are not coincident or parallel, your square is not square.

Dave R.

 

[TemplatesByNumbers]

10digit,
I attach the essence of a method using intersecting arcs to find the corner location for square panels in the PDF document below. A link to a fuller article is here:
http://www.templatesbynumbers.com/?q=geometrylayout
A cabinet build using this method is here http://www.templatesbynumbers.com/?q=makingcabinet
You can use the Festool tape measure to scribe the arcs but be careful to hold the pencil consistently. I tried it to cut some large panels for wardrobe backs http://www.templatesbynumbers.com/?q=viso . To get the best consistency for cabinet builds try making a trammel (effectively a story stick) which will reduce the chances for errors and make it possible to check your work quickly at every stage.
Cheers
Andrew

 

[10digit]

Thank you to everyone who has posted suggestions to create square panels.  Andrew, what you have shown is exactly what I was looking for to use arcs to get it accurate. Dave, I may invest in one of those tri squares you have as well.  When funds permit, I think I will go for an MFT and use its capabilities to get square, repeatable cuts without all of the fuss required with just the detached rail method I am currently using.

 

[nickao]

Templates that's a sweet method.

I am using similar geometry based methods all the time in my work, but I deal in the round and oval mostly. Your method can never be wrong as it is based on mathematical fact.

 

[Notorious T.O.D.]

I would bet that the framing square is not exactly square and the ripped edge form HD is not exactly straight either...so, you are seeing a combination of the errors when you try to cut your 90 degree square cut...

Best,
Todd

 

[JayStPeter]

Before I locked down my angle unit, and even before I went Festool and was using a saw guide,  I used a framing square from either HD or Lowes.  I use a Lee Valley framing square fence.  I check the squares for square all around before I walk out of the store.  I bring a pencil and the LV fence and use the MDF stack to verify the squares.  With all the whining about out of square framing squares, I've had great luck.  I am abusive of them and need to replace them fairly often, but the ones on the shelf are almost always good.  They are easy to mishandle though.

 

[tbellemare]

My Dad taught me to peen an out-of-square framing square with a scratch-awl to get it back to square.

I have his old framing square and it has several dimples at the elbow.

Tom

 

[JayStPeter]

Every time I try to peen the things back to square I can get either the inside or outside back to square, but not both. ???

 

[pci]

Every time I try to peen the things back to square I can get either the inside or outside back to square, but not both. ???

Hi,
i heard about a simple rule (pythagore) to remind: the 3,4,5 rule

square(3?+4?) = 5

The diagonal is 5.

Adjust with a factor, for exemple here: 6

exemple: sqrt((3*6)^2+(4*6)^2)

This way : 18"x24" diagonal is 30"

Hope it helps.

pci.

 

[Notorious T.O.D.]

There can be errors even with mathmatical representations such as solid models in our computers as there is always the decimal precision of the model and also the number of significant places the calculations are carried out to in the end and our ultimate ability to measure them in the real world.

Like the tool and die makers I used to work with always used to say about woodworking... "take it to a 1/64th and just be happy with it...it is wood after all."  They also said the hardest thing that you could try to build ot of wood would be a cube...maybe that is why we see so few wooden cubes....

Best,
Notorious

 

[nickao]

I think the hardest thing to make is actually a perfectly spherical solid wood ball.

1/64" is more than adequate for sure. I can spit on the wood and get it to move that much.

 

[John Stevens]

How do you get accurate square panels? [snip]

I recall seeing a method of stiking two arcs to get a more accurate measure point than can be achieved from a square but cannot locate the article.

Here's how I get things as perfectly square as I can measure with feeler gauges:

http://festoolownersgroup.com/index.php?topic=459.msg3962#msg3962

Even when using squares that check as accurate by the "pencil line" method, I find that the "double error" method yields improvement.

Back when I was a drafting student, I used the arc method while drawing.  I found that no matter how careful I was, I would always end up with measurable inaccuracy in the drawing.  Based on that experience, I would not recommend it for the shop, especially given the success I've had with the double-error squaring method.

Just my two cents, "your milage may vary."

Regards,

John

 

[nickao]

I do not get that I use my HUGE dividers and the arc method for tons of stuff in the shop.

The way templates by numbers uses a trammel I do not see how it could not work as the points are fixed on the trammel.