# making an octogon-cont.



## TJ65 (Jan 19, 2010)

Ok, I have been trying to cut the 22.5 degrees of an angle for a perfect cut to produce a octogon. The problem is I will cut the timber on a bandsaw then perfect the angle using a sander. My problem after countless hours of trying to get the PERFECT 22.5 angle, (to make a template for a triangle so I can then use the gizmo on the machine to make the correct adjustment to it) From there I can sand the angle to the perfect and correct angle. 
Yea, you might say - just mark out 22.5 on the protractor and go from there. Or make a cardboard cutout of a 22.5 triangle and then adjust the gizmo. Or make use a ready made octogon and use that angle. 
*WELL I HAVE TRIED AND FAILED* on all accounts there. I must have spent over 8 or hours to get this prefect template - I am nearly there but still not perfect.
PLEASE tell me is there an easy way of cutting out a template so i can then ajust the gizmo/protractor thingo that you get with machines accordingly to sand and achieve the perfect angle.

(this is alot harder than it looks!!)


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## TopamaxSurvivor (May 2, 2008)

Theresa, the easiest way is mark and then overlap 2 pieces and make the cuts.


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## TopamaxSurvivor (May 2, 2008)

I hope that wasn't too short and blunt. What I mean is to sake the 2 pieces where the t 22.5 degree angles will meet and overlap them, cutting them both at the same time. If one is off, the other will be correspondingly off the opposite amount.


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## sammouri (Dec 12, 2009)

Hi Theresa, there are many factors to make an octogon or any shape perfect. Here are the most important three. A- The presice angle. B- The verticality of the saw. C- The presice equal length of all segments.
REMEMBER: Ajusting the angle by using sanding disc will change the length of the segment. It means you solve one problem and you creat another.
If you combined all the three factors above in one cut you would have perfect octogon.
Good luck.


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## Bob Collins (Apr 25, 2008)

Know how you feel Theresa, I am still trying to get the angles perfect on the segments. I use the table saw and always check that the blade is at right angles before each project but getting the angle spot on is the killer. Wouldn't say that you have failed after eight hours. Have you tried surfing the NET for the setting out of an octogon. Never know. Sorry I don't know an easy way for you but I'm sure you will get it right.


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## Bob Collins (Apr 25, 2008)

Back again, I went on the net, logged in"Setting Out an Octogon" and theres one showing how to cut out an octogon blank from Onlinwoodturning and a chart on www.htmliseasy.com. There could be more. Hope this helps.


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## TJ65 (Jan 19, 2010)

Thanks, the only reason I am planning to use the sander is that the bandsaw will wander a little (as i out found with the picture frames I recently did and this was the easiest way to rectify the lack of precision cutting )
Bob, I tried finding a picture on the internet of an octogon and copying it , that didn't work either.
Might just have to go with what topamax said and try cutting the two out.

If this keeps on going dont know if hubby will get his clock


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## TopamaxSurvivor (May 2, 2008)

If you don't have a table saw, I would arrange the pieces in an octagon, then use a small hand saw, like maybe a gent's saw to cut them two pieces at a time. Gent's saws are fairly inexpensive. That would keep your sanding to a minimum. Like Sam said, when you sand you change the lenght by sanding you open up angles ;-((

You can hold them all in place with a little glue that is easy to break loose like hot glue. Once they are all cut at the same time, you got it!! Might want to use a square board as a saw guide to keep everything square ;-) If the pieces are in a octagon when yoiu start the pieces should go back pretty close )


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## rance (Sep 30, 2009)

Theresa, I believe you are experiencing the same problem as making a mitered box. You can google it or search here on LJ. Here's the short version, whether a square or an octagon(anything with an even number of equal length sides):

1) Rough cut pieces a little long
2) Miter one end of all pieces with your BS
3) Sand that one end to precision with your disk/belt sander(to precision)
4) Cut the 2nd end a tad long on all pieces
5) Set up a stop block to both bring them to exact length AND to clean up the miter on your sander
6) Dry fit by holding them together with a rubber band
7) For an octagon, apply glue to all miters except 2 on opposite sides
8) After dry, on a flat surface(Table Saw surface), sand each clamshell to perfect flatness
9) Glue the clamshells together.

You can also search procedures for segmented bowls to get more details on the above. 
HTH.


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## ksSlim (Jun 27, 2010)

Are you attempting to construct a frame, box, table top or turning blank?
When I do frames, boxes or table tops, I use an adjustable arm on a shooting board to ensure all pieces match.
If your trying to make a template, lay out a complete hex on pattern stock, cut it in half point to point, that should leave at least 4 chances to cut one perfect pie shaped piece.

http://www.htmliseasy.com/octagon_layout/

Lacking a table or miter saw, a fine tooth hand saw will make precisiion cuts.

Hand in there, you'll meet the challenge.


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## stefang (Apr 9, 2009)

Hi Theresa, I think you are on the right track with the sander, but it's not just about getting the angle right. You also have to get the individual slices exactly the same size. The best way to do this is with a sanding jig. Here is an example of one I use for making segments.

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This particular jig would have to have a wider fence for large pieces. I found an idea here that gives an idea what I'm talking about.

http://www.google.no/imgres?imgurl=http://www.woodpeck.com/media/main_Plan4_Disc-Sander-Jig.jpg&imgrefurl=http://www.woodpeck.com/builditstarterkit.html&h=323&w=450&sz=25&tbnid=PufWmM62LvgJMM:&tbnh=91&tbnw=127&prev=/images%3Fq%3Dsanding%2Bjig&zoom=1&q=sanding+jig&usg=__H53nHXbGeNgWRoqO4wTyaSkQXCs=&sa=X&ei=i2o9Tc6pHsWhOv-2ncYL&ved=0CBoQ9QEwAA

I would make something similar to this by having a sliding auxiliary table that fits your disk sander table (with a runner on the bottom that fits into the sander's miter slot. Then just carpet tape a fence on it at the correct angle and with the correct opening so you can shove the point of your workpieces tight in between the disk and the fence. Then slide the auxiliary table against the rotation of the sander to sand the one side of each piece. Next carpet tape a thin strip of something with a consistent thickness against the edge of the fence to make the opening slightly smaller. Now sand the other edge of each piece. You should now have 8 pieces exactly the same size.

Hope this helps you out.


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## Cosmicsniper (Oct 2, 2009)

Theresa:

I've found it's not that difficult if you do as follows (which works with any miter) ...

1.) Cut your sides using your miter saw for the most accurate fit you can (22.5 degrees in your case). Each piece should be slightly longer, the extra length being the width of the kerf of a hand-held miter saw. 
2.) Place the pieces together on a scrap backer-board, in a best fit arrangement, using clamps to hold the pieces down. Surely, you have enough clamps, right? 
3.) Use the aforementioned hand-held miter saw and saw through each miter at each joint. 
4.) You should catch part of BOTH boards within the kerf of the cut. 
5.) Unclamp, re-fit, and glue 'em up.

The procedure might have to repeated if your original angles were greatly off, but eventually those miters will close up perfectly.

Hope this helps…


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## Roger Clark aka Rex (Dec 30, 2008)

Here is a very nice Jig that is foolproof. It's a worthwhile tool if you have a the need to make several different #of sided structures, as it was set the blade accurately and instantly. It is also well made and substantial.

Take a look.

http://www.leevalley.com/US/wood/page.aspx?cat=1,43513,43553&p=32521


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## mpounders (Jun 22, 2010)

Here's a link to Susan Irish's web site….her method is simple enough that I understand it! It might help you to get that one magic segment you are looking for and then use that as your gauge to set up your other equipment to repeat it? I am speaking as someone with absolutely no experience in doing this!


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## TJ65 (Jan 19, 2010)

Thanks heaps.
A lot of thinking and experimenting is going to be done!!


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## bobsmyuncle (Jan 12, 2011)

Here is a way to make a template. The example even shows 22.5 degree cut. You don't need the whole triangle to set your gauge, just a corner.
http://www.thormon.com/basmath.htm


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## BertFlores58 (May 26, 2010)

Hi Theresa,
All of the above comments are requiring lot of tools and absolutely making a wrong assumption regarding making regular polygons. 360 degrees dividing into n sides… but cutting side from 90 degrees will be diffrent in reality. The angle formed will be …... 67.5 degrees.. Please take how it looks now below.










You can make a jig as per drawing in brown. You can use any saw… Hope this will enlighten and help you better than previous…


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## BertFlores58 (May 26, 2010)

For bigger viewing….. have the following and foun out that if you have a miter saw then you have to cut still 22.5 deg outer side reference.


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## woodjewelry (Jun 9, 2010)

Cut a piece of wood to a 112.5 degree angle. Use this as a template. If you put your work piece against this and cut at 90 degrees you will get a 67,5 degree cut (180 - 112.5=67.5)


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## rance (Sep 30, 2009)

TJ,

The angle AND the length are critical. How you get there is irrelevant(as others have alluded to).

ksSlim,

Thanks for that link.


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