next »

[Scott Peterson]

I wouldn't say the microwave is a bad idea - just if there is metal inside anywhere.  If the water/moisture of whatever is making the threads stick can be excited a little, that might get the puzzle unstuck with less heat involved than the oven...

[Robert Yarger]

Wax would probably melt well into the threads in an oven a 120 degrees, but it would compound the problem and act like cement once it reached room temp again.  It is fine to wax it once you get it free, but I would hesitate trying that approach to begin with.  

In fact, I would try the opposite and put in in the freezer first to hopefully "shrink" the wood.  Also, I am not familiar with the puzzle, but are you sure that you have discovered all the restricting devices that might still be in place.  Ther might still be a pin or something that is part of the puzzle that you have not noticed yet.  It would be a bum deal to finally force it open and realize that it was not supposed to open yet.

[Phil Tomlinson]

my two cents (sense? scents?):

If, as Robert said, there really isn't a pin or some other needed action to get it apart, then it is probably a mix of humidity and dirt that are creating the problem.  Cross grain swelling/shrinking at different rates between two pieces.  Using a freezer or low-temp oven might give you enough change to get them apart.  You might also dry a dry-lube product that is rated safe for wood. (see links below)

If you do manage to get them apart, try gently cleaning the threads and most important, try to get the pieces into a stable humidity environment (generally, 50% RH is about right), and let them stabilize before you put them together. 

https://www.expeditionexchange.com/cart/product.php?productid=19504&cat=0&page=1
http://www.sheetmusic1.com/lubricants.html
http://www.rvupgradestore.com/index.asp?PageAction=VIEWPROD&ProdID=819

etc.