Antique bed rail extension

I'm looking for advice/guidance. I apologize in advance for the length of this post. Here's the situation. I've got an antique bed made of oak that is wide enough for a full mattress, but not long enough. The original design called for ropes to be looped around pegs inserted into 3" diameter rails around the periphery of the bed. Then, a feather mattress would sit on top of the woven ropes. I want to put a full boxspring and mattress on this wood frame. I need to extend the length of the side rails by 5". The side rails are 3" in diameter with threaded ends. The threads are reversed on one side so that when the rail is turned it screws into the headboard and footboard simultaneously. Actually a pretty ingenious design that I would like to maintain. What I plan to do is cut the rail an inch or two behind one of the threaded ends and put in a 5" oak dowel extension. I know this will require a precise cross-cuts and I'll probably have to go to my local hardware store to have the cut done there with their radial arm saw since I only have hand tools at home. My plan is to join the three pieces (existing end with threads, 5" extension piece and remaining rail) by drilling a 1/2" hole down the middle, applying glue and using a 10 or 12" lag screw to join and hold all three pieces together. I hope this gives enough detail. Here are my specific questions:
How can I arrange the existing rail and extension oak dowel rod so they are cut precisely and will make a straight rail when they are joined together?
How can I maximize the chances of drilling a 10-12" hole down the center of all pieces so the resulting extended rail is straight?
Is there a better way of doing all this?
Thanks in advance for any help.
Dave
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To be done right, take the rails to a local furniture or cabinet builder and have them do all the work. It may require totally new rails. I would not leave this up to any one that cannot do the whole process start to finish.
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snipped-for-privacy@dwburger.ws wrote: ...

I'm w/ Leon here...the stress in the joint is going to be intense and the closer you place it to the end, the more difficult it is. _IF_ (that's the proverbial "big if") I were to try somesuch I'd make the joint in the middle and rather than try to insert a piece w/ two square ends I would use a very elongated scarf joint. I'd then insert a dowel as you suggest and glue it.
To drill the concentric hole precisely enough really would need a large lathe mounting -- I suspect this was originally turned that way on a special-purpose long lathe for the purpose.
I'm curious from your description -- are the threads on each end wooden or is there a metal threaded insert? I've never seen the design of LH/RH threads--that is pretty unique.
--
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dpb wrote: ...

That, of course means turning a section to insert and cutting the scarf on both ends of it...
The thing w/ this would be that it could be left somewhat oversized initially and then the lengthened rail turned as a whole to fair the new work in. (Of course, that could be done w/ the square-ended piece, too, but it would rely entirely on the internal dowel for strength whereas the scarf joint would have a large glue area and be quite strong if well done.
--
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On Fri, 14 Mar 2008 14:38:37 -0700, snipped-for-privacy@dwburger.ws wrote:

Best - Make new side rails out of one length of wood. A good (but not cheap working) finisher / restorer should be able to make the finish look authentic. Hardware can be reused. I make small replacement parts for historic buildings, and there is a large amount of unsung (yet billed by the hour) labor involved in matching an old item.
2nd Best - "Sister" a new board in from behind. This gives lots of glue area. You'll still need the finisher from the choice above to match the new section. Since wood is almost impossible to match, GOTO "Best", as the joint created by this choice will most certainly be visible.
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snipped-for-privacy@dwburger.ws wrote: : diameter with threaded ends. The threads are reversed on one side so : that when the rail is turned it screws into the headboard and : footboard simultaneously.
Note that the threads at the two heads snug up at the same time. If you rotate one end relative to the other, you may end up with a loose joint at one end when the other end is tight.
I think you'll have better results if you sister or scarf in an oversize piece and then use a scraper, spoke-shave, sand paper, etc to create the final shape and smooth the transition.
--- Chip
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Chip Buchholtz wrote:

<Great> minds and all that... :) --
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