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I would appreciate help so much!

I am trying to make a 'collapsible' arbor if you will. I would ideally like to saw my large birch posts in half and make them screw back together in the center, but I have no idea how the mechanics of such a thing would work. Double headed large screws!? Any suggestions would be appreciated.

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2 Answers

The birch posts in the original design were made a certain length to serve a particular function. I am sure they were selected on the basis of strength, stability, and durability. As a first order analysis the idea to cut them in half seems to defeat almost all the reasons that they were designed for in the first place.

It will not be possible to simply cut the posts in half and re-join them in a manner that will restore them 100% back to the original look and function. That said there may be some ways to come close to that as possible if one can look past the cut lines and some fasteners / bolts.

There is some missing information that will be needed to provide the overall solution and/or suggestions. I can provide one possible idea for the case where these posts are deployed in a vertical orientation and the girth of the post is substantial.

The idea is to go ahead and cut the post in half and then install a heavy piece of steel pipe into a hole drilled into each end of the post. The pipe would be glued into the lower hole using construction grade adhesive. Cross holes would be drilled though the sides of the upper post to accept bolts that would be threaded into prepared holes on the other end of the steel pipe. See picture below:

enter image description here

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Good design, mechanically. Might be hard for average homeowner to drill deep enough (and large enough) to support a 6-8 ft high arbor. I'd fill tube with mortar and use through bolts. –  HerrBag Jun 20 '13 at 15:52
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Bolt heads could be countersunk to improve appearance (if material is thick enough). –  Steve Fallows Jun 20 '13 at 21:27
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Two half-lap joints with through bolted hardware.. not invisible, but solid:

  1. Cut post in half, but leave room for the mend plate on lower half
  2. Cut out half of each side of the splice (perhaps one foot each). Pick the the front or rear side (perpendicular to arch)
  3. Make a "mend plate" that will span both sides (replacing the 2 pieces you just cut out). (2 feet long if each side of splice is 1 foot.
  4. Assemble with hot-dipped galvanized hardware (9/16 or 5/8 carriage bolts) such that you clamp the mend plate against two "legs" of the original posts.

enter image description here

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Why not flip one of the posts 180 degrees so the two cut out sections interconnect each other and skip the mend plate? Wouldn't that be sturdier? –  gregmac Jun 20 '13 at 17:59
    
@gregmac Possibly but would reduce the arbor by a foot of height, probably not OK. Plus, flipping not practical with existing arbor –  HerrBag Jun 20 '13 at 18:19
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