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  1. #1
    Join Date
    Jun 2004
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    sonoma ,calif
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    Default cutting an octagon

    making an octagon table .made a test run this evening with mitersaw .it was ok ,would need to do some tweaking on the last one . will try the mft table and guide rail tomorrow . Thought someone might have advice .
    I am really not confident that our major brand miter saws are made for such accuracy . mine are all 12" ,i can feel the blade pulling on the board towards the end of the cut so the mft and 55 saw might be smoother and reduce some err .

  2. #2
    Join Date
    Feb 2008
    Location
    Northwest Indiana
    Posts
    5,576

    Default Re: cutting an octagon

    Seeing as you need to cut 22.5º angles. Get a couple of 20mm bolts (shank size, not head size) to fit the holes in the MFT top. Place 1 bolt in a hole that is close to, but clears the cross cut rail and as far from the front edge as possible. Starting with the bolt, count 3 holes towards the front of the table, then count 6 holes left, insert the second bolt. Use the fence to align the bolt heads. Assuming you have calibrated the cross cut fence, you now have a perfect 22.5º angle. You can remove the bolts and place the material against the fence (once you lock it all in place aligned to the bolt heads) or place the material against the bolt heads.

    If you have clamping elements, and are confident in your "feel" you can use the stationary side of the element in leu of bolts. They fit the holes perfectly, but you have to be careful not to push unevenly on the rubber face.

    There are dogs available for this, I don't have any, so I improvise.

    Forgot to include- clamp the piece to be cut, sharp blade. With a little experimentation, you will find there are other angles bolts in the holes create.

    Tom
    Last edited by tjbnwi; 05-07-2012 at 07:29 AM.
    http://chicagocraftsmen.org/2011/06/261.html

    Check with the AHJ, what we say doesn't matter.

  3. #3
    Join Date
    Jun 2004
    Location
    sonoma ,calif
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    Default Re: cutting an octagon

    I have Dogs ! Thankyou -that is a great tip . Joseph

  4. #4
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    Jun 2004
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    sonoma ,calif
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    Default Re: cutting an octagon

    Just wanted to report I used a dewalt non sliding 12" saw with a new forest blade to cut the 8/ 22.5 º pieces .used dominos and pocket screws to pull it together .I was wrong about what this saw would do . It is perfect , no gaps .I was impressed .Had a lesser quality blade in at first and not as good of a line-up .

  5. #5
    Join Date
    Sep 2004
    Location
    down the shore
    Posts
    2,214

    Default Re: cutting an octagon

    I always thought this JLC tool test was interesting. Tested miter saws by cutting octagons. Some of the saws were pretty accurate:

    http://www.jlconline.com/cgi-local/v...170a323cb406a8

  6. #6
    Join Date
    Feb 2008
    Location
    Northwest Indiana
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    5,576

    Default Re: cutting an octagon

    I have always read that a "chop" miter saw is more accurate than a slider. Fewer moving parts, less slop.

    Tom
    http://chicagocraftsmen.org/2011/06/261.html

    Check with the AHJ, what we say doesn't matter.

  7. #7
    Join Date
    Jun 2004
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    sonoma ,calif
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    Default Re: cutting an octagon

    I should go on woodweb and see how others do this .I was going to do a table for a client but now I am not so sure .This was a test run I figured I would keep .When I 1st reported I had gotten the 1st outer ring done .Though they did not look perfect on the dry fit when the pocket screws went in it pulled up perfectly ,I was very impressed.But as the ring got smaller gaps got bigger . The dry fit could look perfect but when i tightened up the joints with screws they changed . So once you have your dominos or biscuits all glued up and pulled together it is not like you can unassemble and start tweaking miters .there are some small gaps . I used dominos because they have the ext ones but as it got smaller the biscuits became by far the better choice .Used TB111 .clear redwood salvaged from an old hot tub .Pocket screws were used to pull the joints tight .
    Attached Images Attached Images

  8. #8
    Join Date
    Jan 2008
    Location
    Berwyn, PA
    Posts
    766

    Default Re: cutting an octagon

    looks great! You would make $2/hr on this one.
    Josh O.


    "If people knew how hard I worked to achieve my mastery, it wouldn't seem so wonderful after all. "

    - Michelangelo-

  9. #9
    Join Date
    Feb 2008
    Location
    Northwest Indiana
    Posts
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    Default Re: cutting an octagon

    Use a strap clamp to pull it together, then tighten the screws?

    Tom
    http://chicagocraftsmen.org/2011/06/261.html

    Check with the AHJ, what we say doesn't matter.

  10. #10
    Join Date
    Apr 2006
    Posts
    65

    Default Re: cutting an octagon

    You going to put this outside? Those miters look great right now, but over time, outdoors, they will open up. I would put a small chamfer at the joint line to hide the fact that the miters will not remain tight

    (new member since 2006)
    Last edited by Jerry M; 05-12-2012 at 12:05 AM.
    ---Jerry

    Try to learn from other people's mistakes---you'll never have time to make them all yourself

  11. #11
    Join Date
    Jun 2004
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    sonoma ,calif
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    Default Re: cutting an octagon

    I have been using biscuits, screws and TB111 and getting good results .The picture of the handrail is more just to share something that worked ,these miters are not under the same load .It is several years old and all joints are perfect . I was at some stairs I did roughly 7 years prior ,there are 10 miters .of those 10 one is slightly opened .fully exposed to the weather . Clients probable do not notice the nice joints but I do . I am impressed . For the most part the miters I am doing in exterior stairs and deck railings are holding tight .
    The table top is from an old hot tub .Super nice wood . Table will not get full exposure . I do wish they were all real tight from the start though . I assembled it from the backside using pocket screws to pull the joints tight . After it dried and I rolled it over to sand I find little gaps . Maxium width would be the thickness of a cheap business card .The pocket screws had little grab in this straight grain dry soft redwood .
    Attached Images Attached Images

  12. #12
    Join Date
    Sep 2004
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    5,888

    Default Re: cutting an octagon

    Beautiful work Joseph.

    On the subject of mitres opening up when exposed to the elements.

    Living in a climate that swings from 90+ degree high humidity summers to -25 dry arctic cold spells in the winter keeping mitres together that are exposed to the weather is always going to be doomed to failure.

    I am building some outdoor furniture at the moment that doesn't feature mitres but is made up of live edge laminated slabs and tight mortise and tenon joinery. I want it to have a furniture grade clear finish so I did a little research and have decided to try the System Three epoxy finishing system http://www.systemthree.com/reslibrar..._finishing.pdf consisting of a low viscosity penetrating epoxy sealer and a satin epoxy "spar varnish" I haven't used it yet, it's in transit at the moment but I am hopeful that this allows me to make some high end furniture and millwork that can endure the climate.

    This may be a solution to insure that finished woodwork stays clean, stable and beautiful in any environment. Apparently the sealer alone petrifies the wood and is compatible with a range of finishes and the system 3 epoxies can be tinted with transtint dyes.
    Last edited by dave_k; 05-12-2012 at 09:51 AM.

  13. #13
    Join Date
    Jun 2004
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    sonoma ,calif
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    Default Re: cutting an octagon

    Yeah i was thinking my luck with out side miters could be due somepart to the climate . It is pretty stable weather .
    Dave is this furniture your building for yourself or a client . This table I will not be selling .I was thinking or preparing myself to keep it when I started .The octagon shape just is not worth the labor with what I know now .I see in high end catalogues fancy exterior furiture .They are probable doing a finish like you are using .I would like to see pictures .I need ideas ,Client still wants two tables.
    Joseph

  14. #14
    Join Date
    Sep 2004
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    5,888

    Default Re: cutting an octagon

    Quote Originally Posted by joseph View Post
    Dave is this furniture your building for yourself or a client .
    This one's for me however I have one order from someone who's seen the table and a dealer is coming by next week (my wife's idea).
    Quote Originally Posted by joseph View Post
    I would like to see pictures . I need ideas ,Client still wants two tables.
    Joseph
    I'll post pics and share details about the finish.

  15. #15
    Join Date
    Sep 2004
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    5,888

    Default Re: cutting an octagon

    This is the table http://www.flickr.com/photos/5559328...7629732411452/

    I still don't have the finish. When I get I'll document finishing the table and post some pictures. I'm really hoping this finish allows me to make outdoor furniture out of wood that holds up over time and can be finished like indoor furniture.

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