Is this gap acceptable for a glue up?

[Michael Weber]

Using a feeler gauge there is a a consistent gap of .003 inches in the middle of 15 inch long cherry boards I need to glue up edge to edge. That is, each board is bowed by half that amount. It's the best I can do with current circumstances. Boards are 7/8 inch thick and 3 to 5 inches wide. If I crank down on the clamps to squeeze them together during glue up will they stay or do I need to reduce the gap further? Don't want them coming apart in the future. There will be 2 to 3 boards in each glued up panel to get the needed width. Thanks

[David Duke]

I think this thread pretty much covers .003 gaps.............. http://www.sawmillcreek.org/showthread.php?t=67721

[Pete Brown]

Put the feeler gauge away when working wood :)

I recently read an article (I forget where) that actually advocated a very slight dish in the center edge to ensure that the ends were extra tight.

Pete

[Michael Weber]

My concern is that the boards are so short. If they were 3 feet long I wouldn't worry about it.

[Greg Muller]

Another woodworker with a feeler gauge.

Mke, put the gauge down on the ground and back away slowly and no one will get hurt. :rolleyes:

[Greg Funk]

I suspect if you put a clamp in the middle you could close up that gap with less than 20lbs of force. The glue is much stronger than that and it won't have any problem keeping that closed. As others have recommended: throw away your feeler gauge!

Greg

[Denny Rice]

Mike,
Your kidding right??? Put the feeler gauges and the micrometers in the machinist toolbox.:D Just kidding, you should be proud, I know I would!

[sascha gast]

:confused:

[Greg Cole]

What they said about ww'ing and a feeler gauge, just put it down.....
Unless you are setting up a tool in the shop.
Holding boards edge to edge up to a light works for me :rolleyes: .
I believe it's referred to as a "spring joint" when you intentionally gap the boards as described by the OP?

$0.02 donation.

Greg

[Michael Weber]

Mike,
Your kidding right??? Put the feeler gauges and the micrometers in the machinist toolbox.:D Just kidding, you should be proud, I know I would!

OK, OK! :D I only used the gauge so I could say what the gap was. I normally hold up to a light. But, saying I see light between boards was only going to get "How much light" responses. BTW, the outfeed table of my Delta 37-190 jointer sags down which is why I always get this little bow. Maybe its a good thing;)

[SCOTT ANDREWS]

If there is a known problem with the jointer,I would spend some time tuning it up and try to eliminate the problems you are having.That is the purpose of the jointer is to make things square and flat so you have something to start with that isn't bowed.

[Gary Keedwell]

Welllllll Just back from vacation and getting the urge to get back into the fray. IMNSHO... I would forget what everybody above said and listen only to me.:eek: :) Only kidding.....You sound like you got yourself a jointer tune-up due in the near future. If you can see light between boards a little over a foot long....well, what's it going to look like when it is 4 feet long?:rolleyes:

I would start with a good straight edge and go from there. With only 15" there is absolutely no reason to see light between boards. Heck, I could put sticky sandpaper on a table saw top and rub the board back and forth and NOT see light. I'm in the school of thought that you should be able to put all your boards together, side by side, and lightly put them together using your hands and not see light.
I may get some flak here, but I don't believe in putting wood under any unnecessary stress.:)

Gary

[Cliff Rohrabacher]

If I can hold the boards up and see light - any light shining through I re-joint it.

Call me picky but I don't trust any glue other than resorcinol (formaldehyde glues) to resist cold creep. All other glues that I know about are polymer glues. All of 'em. This means that by definition they are all subject to cold creep. Epoxies, PVA, white glue, yellow glue - - you name it they are all polymers and all polymers are subject to cold creep.

Cold creep is exacerbated and usually caused by constant or even extended periods tension on the joint. The lignin in a 15" cherry board isn't going to give up the ghost. and let the wood cells relax into the position you force it into when you apply clamps.

That of course means that the boards will always tending to return to their original shape and eventually the glue should creep and then a little later on it should fail.

It is my hope and effort to always have my boards and joints under zero stress when they are in their assembled and resting state.



Because of the tendency of all polymers to creep engineers have experimented with many way to reduce the phenomena. They add mineral fibers to polymers as well as talc trying to increase rigidity and eliminate creep. It sort of kind of works.
However Talc weakens polymers substantially and fibers would also were it not for the redistribution of stress. They are however, abrasive and wear out injection molds rather quickly.

But they still experience cold creep just less of it.

Rulon is a polymer that engineered without additives to resist cold creep. Rulon is a re-manufactured Teflon that is re-manufactured with some kind of fibers that generate during the re-polymerization. They and other elements about the re-polymerization are intended to prevent it from creeping under load and make it stiffer. Rulon is used in highly stressed dynamic and especially static load applications. It makes a good shaft bushing material. I believe that Rulon has been experimented with as an earthquake isolation bearing for buildings.

[Michael Weber]

If there is a known problem with the jointer,I would spend some time tuning it up and try to eliminate the problems you are having.That is the purpose of the jointer is to make things square and flat so you have something to start with that isn't bowed.

Well the jointer is tuned to a fare-thee-well. Knives set correctly, etc. But reading online threads about the sag in the outfeed indicates that there is no solution to that. I tried by using the gibs but that didn't do anything. As I understand it, thats not a function of the gibs anyway. Even applied upward force to the end of the table as I messed with the gibs. If I was a SERIOUS woodworker or trying to make high quality furniture I'd replace it. But........

[Gary Keedwell]

Well the jointer is tuned to a fare-thee-well. Knives set correctly, etc. But reading online threads about the sag in the outfeed indicates that there is no solution to that. I tried by using the gibs but that didn't do anything. As I understand it, thats not a function of the gibs anyway. Even applied upward force to the end of the table as I messed with the gibs. If I was a SERIOUS woodworker or trying to make high quality furniture I'd replace it. But........
It seems to me that there has to be some kind of FIX for your jointer. It wasn't designed from the factory to sag like that. Maybe someone who has more experience in bringing life to old machines will chime in here. What jointer do you have and how old is it? Must be someway to co-plane that sucker up.;)
Gary

[glenn bradley]

Some people advocate the gap as closing under pressure during glue up yeields a tight glue line visually. Other folks prefer it be a nice fit to begin with. Both methods are used, both work. Sorry you took so much heat for the feeler gauge thing. I realize you were just trying to report your variance accuratly. Your material will move more than that over the course of the day.

[Warren Clemans]

But reading online threads about the sag in the outfeed indicates that there is no solution to that.

Assuming the outfeed table is flat, you should be able to shim it so the tables are coplanar. Lee Valley sells a handy assortment of shim stock. Lay a good straightedge across the tables and shim the bottom of the ways until the tables are aligned. Good luck!