Green Cedar, Wood Shrinkage, and Furniture Joinery

      A discussion of whether to worry about what's green and what's dry when making roundwood furniture from Cedar. June 30, 2009

Question
I am trying to start building log furniture using cedar logs. The logs I will mostly be using will be from 2" to 5" inches in diameter. Do I need to dry them before I cut tenons and mortises to avoid shrinkage and if so how long must I air dry them? Air drying is currently the only available method for me to use.

Forum Responses
(Sawing and Drying Forum)
From contributor C:
It takes about six months to a year for cedar logs to dry. Stack them so that the air freely moves through them. If you want the character of staining and bug tracks leave them for a year or more. Also they peel very easy. If you have a German type peeler, you can peel them green. You will have a little checking, but they will dry faster.



From contributor B:
I had another thought. If youíre not needing truckload volumes of dry cedar per day, have you thought about harvesting the standing dead cedars in the stand or in the forest? Many small ones die out and will stand for years in good condition and become dry to the bone.


From the original questioner:
I have been looking for standing dead cedar but haven't had a lot of time to do so. I am wondering if I should use green wood because I am starting to build log furniture using only hand tools.


From contributor T:
Maybe this will complicate things some, but consider assembling pieces that have mortices green, and pieces that have tenons dry. This way as the green mortices dry they will shrink on the tenons and tighten up. So the logical question is: what do you do when a single piece that has both tenons and mortices?


From contributor S:
Contributor T - I think you would be going to a lot of trouble for a little benefit. While a dry tenon has shrunk radially and tangentially, as wood shrinks the most, a mortise is most of the time dealing in a length dimension that does not shrink near as much, if any. To rephrase, wood does not shrink along its length much.


From contributor C:
Grab a few green logs and make a few pieces of furniture. See how they hang together after putting them in the house for a few months of low humidity. I think your question of whether to use green logs will be answered. Then you can tell us and that will be that.


From contributor B:
I agree with contributor T. A lot of mortises in rustic furniture would be round ones. If a piece was green and you drilled round holes for the mortises the holes would tighten up on the tenon when dry if the tenon was already dry. If the tenon is as wet as the mortise I think the joint would not be as tight after all is finished drying.


From contributor T:
Youíre correct in that a mortise will not shrink much along the length of the grain but across the grain is a different story. So a round hole drilled in green wood will end up somewhat ovate after drying. Properly executed this can be a vice-like grip.


From contributor S:
Itís a round mortise, so it shrinks ovate due to the differential shrinking of the tangential, radial, and lengthwise directions of grain. So how is the hole going to shrink to tighten the joint, unless you carefully orient the grain patterns to match. Glue is cheap, compared to the thinking involved in this exercise.


From contributor C:
Remember, we're dealing with ERC. Green heartwood is rather dry to begin with and ERC shrinks the least of our native woods, at least in Indiana. The tenon will most likely be all heartwood and the outside of the mortise will most likely be sapwood which will do the shrinking.


From contributor E
On several occasions I have watched a chairmaker at the Harpers Ferry, WV craft show. This is a juried show with only the best craftsmen invited. He would use all air dried lumber (about 12% in this area). He would make the tenon just slightly larger than the mortise. Then he would place the tenon in a bucket of very hot sand to dry just the tenon. Then after it was dry he would quickly place it in the mortise with the grain running opposite the mortise. His explanation was the tenon will return to its original size of just larger than the mortise and make a solid joint. Also, making the tenon grain opposite the mortise, would make it tighter as the tenon would shrink less than the mortise, further tightening the joint if the chair was used inside. He was at the show for years, so it worked for him.


From contributor S:
If you are making rustic furniture, you might consider using slightly tapered mortise and tenons and they could be tightened as needed indefinitely.


From the original questioner:
Contributor E - did you see how that guy heated up the sand bucket?


From contributor E:
He used a small propane burner under a cast iron bucket/pan. The sand only has to be a couple of inches deep, just enough to place the tenon in it while leaning it on side of pan for a while to dry it out. He would have a few in it drying while doing other stuff.



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