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how much spring in a spring joint

5/26/15       
the google

understanding that spring joints can be a good thing (especially, when we simply cannot joint straight, straight), is there a rule of thumb as to how much gap over a given distance?

we run aren't able to get our equipment to joint truly straight at 10' and beyond but our jointer will put a spring in our joint. typically, we're a 1/16" from touching at the center of 10-12' long pieces. the pieces come together evenly and typically with regular clamping pressure (not light but not extreme).

is this an acceptable spring, or do we have too much spring in our joint?

5/26/15       #2: how much spring in a spring joint ...
Leo G  Member

Website: http://www.lrgwood.com

1/16" over 10' isn't going to harm anything. The wider the board the longer you should leave things in the clamps. Time to play with the adjustment on the jointer though. You should be able to get it nearly perfect. Over a 10' length most of the time I can get boards within 1/64th of space between them. That's about 1/128th inch curve in each board. It took me about 3 years before I got it that good. I'd get frustrated and play with the adjustment and it'd get closer. I did that about 4-5 times and got nearly perfection. The outfeed table height against TDC of the knife rotation is critical to get a perfectly straight board.

5/27/15       #3: how much spring in a spring joint ...
the google

leo - thanks for your reply. i neglected to mention that we're jointing glue ups, and not single boards.

we have make-shift extension tables on our jointer but we're typically jointing 10'+ x 25-40" glue ups so the weight bears too hard on our extension tables to get things closer to perfect. i'm in the process of getting these tables upgraded to steel and we should be able to get the settings closer to perfect. we generally don't have issues with long, single boards.

5/27/15       #4: how much spring in a spring joint ...
Larry

I've got a 16" jointer with massive' long tables. But it took a lot of fooling around to get it really accurate. Had the tables Blanchard ground. Used a 2 meter long straight edge and a lot of time. Solved the problem, got a straight line rip saw. Far faster and a better glue surface than the jointer.

5/27/15       #5: how much spring in a spring joint ...
Keith Newton

If you are getting deflection in your beds from the weight, you are probably also working your tail off feeding it.

When I'm working with lumber too large to handle on my jointer, I switch to my Makita 6" power plane. It makes a great cut, and side the front knob is also the depth adjustment, I can change it on-the-fly. It is a lot easier to take a <20# tool to the big stuff when it just gets too hard to handle.

Even with a big jointer in the shop, I probably use this thing a couple of times a week, any mine is over 30 years old.

Amazon link to Makita planer

5/28/15       #6: how much spring in a spring joint ...
nicko

could you clamp a straight edge to it and use a router with a spiral bit and take about a 32nd off ? if i understand what you are saying that you are jointing 25 to 40 inch glue ups how are you holding them vertical agains the fence? It seems that would be hard to do

nicko

5/31/15       #7: how much spring in a spring joint ...
Gene Wengert-WoodDoc

Feed tables are seldom perfect flat with the in and out feed aligned with each other. Often the slope is 0.005" per foot of length minimum, but I have seen 0.05" and I like this larger amount.

Due to stresses in wood that are natural, the small amount of deviation you are seeing will not be an issue for most joints I have seen. When gluing long pieces, it is critical that the ends touch, as this is where we will have the most stress and therefore require the most strength in the joint. Of course, if there is too much pressure at the ends, the glue can be squeezed out so much as to create a weak joint.

6/1/15       #8: how much spring in a spring joint ...
the google

dr. gene,

how much pressure is too much (and would cause a bad joint)?

we work in a variety of hardwoods but typically squeeze pieces together as tightly as humanly possible (we don't use pneumatic tighteners). we're using pva glue.

we haven't had any issues so far but i'm curious as to what constitutes too much pressure.


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