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Thread: Finger jointing in wet weather
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17th October 2018, 08:57 AM #1GOLD MEMBER
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Finger jointing in wet weather
With all that is know about the swelling of wood with moisture in the air, how many of you ignore this and use a finger jointer anyway?
i made a dovetail puzzle cube recently and every time we have weather like this, it's a bigger to open.
i was curious as I don't want the wood to swell, then I cut, then it shrinks when dry weather comes around.
its sort of a self answering question really isn't it?
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17th October 2018, 09:07 AM #2
Wouldn't the fingers and slots all expand and contract at the same rate? What has a dovetail puzzle cube got to do with a finger joint box?
Franklin
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17th October 2018, 09:44 AM #3GOLD MEMBER
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17th October 2018, 11:01 AM #4GOLD MEMBER
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a join is really just a set of fingers that are spaced to inter-mesh. So they are going to swell equally, and be hard to mesh together, or they will shrink, and be sloppy. Somewhere you'll get equilibrium. The force transfer will equalise too once the pieces are joined together, but I can see the potential challenges before that!
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17th October 2018, 11:34 AM #5
Presuming we are talking about finger joints across the grain in solid timber. If the joints are cut at the same time on both pieces of timber of the same dryness, the pins and slots will be equal size. Assuming the cross grain movement is equally spread across the board with humidity change, the grain at the ends of the slots expands or contracts the same amount as the grain across the pins because it is the same dimension of cross grain timber. Therefore the slot becomes just as wide as the swollen finger, or just as narrow as a shrinking finger.
Franklin
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17th October 2018, 04:08 PM #6
When you finger joint, isn't the timber grain all going the same direction and therefore both pieces should expand and contract the same amount rather than fighting against each other. With your puzzle, is the grain going the same direction on both halves? It's hard to tell from the photos, but if the grains are at an angle to each other one half will move more than the other therefore changing the clearances.
Dallas
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18th October 2018, 02:48 AM #7GOLD MEMBER
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18th October 2018, 02:58 AM #8GOLD MEMBER
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I know that timber density plays a part also, but I want everyone to try this, cut a finger joint when super dry and no rain for a week or two, then when it rains, try and put the 2 pieces together, I'm tipping that they will be too tight to put together, if done correctly.
It has opened some discussion though. I do however think that to prevent any misfortune, I think I should do on a dry day, as I'm happy for it to swell once cut (before gluing together that is) rather than shrink after cutting, I'm pretty sure the reverse will happen, ie, cut on dry day - tough to connect on a wet day, so using that theory, cut on a wet day, sloppy/open join on a dry day.
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18th October 2018, 05:14 PM #9GOLD MEMBER
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Just to test your theory out Fumbler. I had planned to make some finger joints today in an experimental box. A couple of weeks ago a mate at bowls who works for the roads, got me two very old fence posts, 100 plus years old, made from Rosewood. As you can imagine the outer timber was very weather beaten and it took me a lot of mucking about getting rid of all that, but the inner Rosewood was blood red. I had a simple box in mind where I have ordered some bits and pieces to make very small swivel hinges so thought I would try it out on this Rosewood. The bits and pieces haven't arrived yet.
Here at present after two weeks and 210mm of rain so far, the humidity today is 92%. The joints are a nice fit, lets see if they get loose (Fumbler's theory).
I wont do any gluing until I insert my hinges (if they end up working). I'm also keen to see how this rosewood comes up after some Danish Oil, I think it will just lap it up.
I've only got till the end of next week, then we are to New Zealand for 7 weeks. I've been flat out the last few weeks, had 5 custom order boxes to make, all watch boxes also, plus I made two toy timber trucks for a little 3yo boy over in Uganda, posted them away this week.
Paul
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18th October 2018, 05:48 PM #10
We are in NZ at the moment and about to head home tomorrow. I wish we had 7 weeks as it feels like we have been just driving, driving, driving to try to cover as much as we could in the 2 weeks we had. It's our first time and the country is bigger than what we thought.
Hope you enjoy.Dallas
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18th October 2018, 08:43 PM #11GOLD MEMBER
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hey Dallas, wow, how about that. I hope you had a super time over there. We're only doing the south island and yes looking forward to it. Least it will get me outa my shed for 7 weeks or so,...
Paul
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19th October 2018, 03:55 AM #12GOLD MEMBER
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19th October 2018, 10:25 PM #13GOLD MEMBER
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So whats the go with applying glue to a finger joint joints? I would assume it would be tedious and messy..... yes / no?
Experienced in removing the tree from the furniture
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20th October 2018, 01:53 AM #14GOLD MEMBER
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yes, but t can be done delicately enough to get a relatively clean finish. If you cut the finger depth 1mm deeper than the thickness then the glue squeeze out will be removed when sanding off the fingers. either that or you put tape over the ends, then with a hobby scalpel cut out the slots and wipe off the excess.
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25th October 2018, 02:42 PM #15GOLD MEMBER
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Hi there Fumbler, and others. I just wanted to finish off that little finger joint experiment for Fumbler. Here on the Coffs Coast it is always pretty humid, the other day I put this box together and it was about 87% humidity. Today I note it is 82%, nice clear day. So basically there was no change as to the tightness or looseness of my finger joints. I wanted to make this experimental box to test out a cheap swivel hinge idea. I am always on the lookout for low cost hinge ideas. Previously I have just drilled a hole in the timber and used a 5mm brass rod to swivel inside the timber/lid. This time I come across these little sleeves, they are made from stainless steel and 10mm long with an OD of 2.7mm and a ID of a tad over 2mm. I think they are actually used for making fishing lures. I then sourced some 2mm stainless steel rods.
All the timber in this box is 10mm thick. In the ends of the box I drilled in about 8mm, with a 2.5mm drill bit, then tapped the sleeve in. Didn't take much work on my belt sander to smooth off the 2mm excess of the sleeve. I drilled into the end of the lid but a bit further than 10mm also with a 2.5mm bit. Then I tapped the sleeve into that, and then drilled in further through the sleeve to about 20mm with a 2mm drill bit.
Then I cut out two rods from the 2mm stainless steel rods about 27mm long, and glued it all together.
The resulting hinge is very strong, I am impressed with the result. I'll be able to make a few more smallish type boxes with this concept, getting rid of some of my odd pieces of timber laying about using nice contrasting timbers.
I wont be making any more boxes this year, heading off to NZ on Sunday for 7 weeks.
Paul
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