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how tight do i clamp?

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Forum topic by bygrace posted 08-06-2016 12:08 AM 475 views 1 time favorited 16 replies Add to Favorites Watch
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bygrace

164 posts in 1434 days


08-06-2016 12:08 AM

Topic tags/keywords: question joining

If you look at any of my projects you will see that furniture is new to me. I decided to try and make a little money with my woodworking by building some farmhouse tables. The first came out great, but the second table top “cupped” during glue up. I used 2×6’s for the table top. to try and keep them even during glue up I used 2×4’s on edge, clamped above and below the 2×6’s in three different locations to sandwich the top and keep them even, then used pipe clamps to bring the 2×6’s together for glue up. I screwed down very tight on the pipe clamps. would this have caused the top to “cup” despite my attempt to hold them flat with the 2×4’s? The middle rose about 3/16ths above the edges. Its 40 inches across. Thanks in advance for your advice!

-- Andy, Waxahachie, Tx.


16 replies so far

View nightguy's profile

nightguy

213 posts in 127 days


#1 posted 08-06-2016 12:29 AM

Could have been to tight, snug is good, could have been the edge to face was not a perfect 90*. Hard to say, since not being there.. For sure snug or just past it is sufficient for clamp pressure..

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AlaskaGuy

2406 posts in 1774 days


#2 posted 08-06-2016 12:30 AM

I used 2×6 isn’t a lot of information.

-- Alaskan's for Global warming!

View ki7hy's profile

ki7hy

497 posts in 204 days


#3 posted 08-06-2016 12:38 AM

Construction lumber? If so how long before the cupping appeared after gluing?

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TheFridge

5765 posts in 951 days


#4 posted 08-06-2016 01:01 AM

Happens to me all the time even with cauls.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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bygrace

164 posts in 1434 days


#5 posted 08-06-2016 01:20 AM

nightguy, I milled all the lumber before glue up, so they should’ve been 90*. But I did screw down on the pipe clamps pretty much as tight as I could so I’m thinking that’s what did it, just wasn’t sure.

Alaska guy, sorry about that. I did use construction lumber (Fir). Most of the farmhouse tables are built with it, with hardwood offered by some as an up grade.

ki7hy, I noticed it the next day after I left it to dry overnight.

TheFridge, Cauls. Thanks. I knew there was a name for those! would have been much easier to understand if I had remembered.

-- Andy, Waxahachie, Tx.

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nightguy

213 posts in 127 days


#6 posted 08-06-2016 01:22 AM

I guess trying to make fine furniture from construction lumber is an oxymoron!! If that is the look you want though that is what to use, and old pine back then was different then good pine now a days.

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nightguy

213 posts in 127 days


#7 posted 08-06-2016 01:25 AM

Was that 2×6 pine or Douglas Fir, big difference, 2 different species?

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bygrace

164 posts in 1434 days


#8 posted 08-06-2016 01:36 AM

True nightguy! this is what people are buying right now. Not my first choice either, but I need to support my habit and the tools I need to move forward.

-- Andy, Waxahachie, Tx.

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nightguy

213 posts in 127 days


#9 posted 08-06-2016 01:48 AM



True nightguy! this is what people are buying right now. Not my first choice either, but I need to support my habit and the tools I need to move forward.

- bygrace

Gotta do what you gotta do!!!!!!!!!!!

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jbay

816 posts in 364 days


#10 posted 08-06-2016 02:02 AM

”how tight do i clamp?”

Apparently, as tight as you can… LOL

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

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jumbojack

1667 posts in 2089 days


#11 posted 08-06-2016 02:39 AM

Generally, only tighten enough to close the gap and produce beads of squeeze out. Sometimes it also helps to alternate the end grain structure. That is ring smiles up and down. Further if you brought the lumber home cleaned them up and glued them you glued up wet lumber. It is difficult to get dry lumber at the box store. If I need to use the lumber right away look for kiln dried lumber. For best results look for grain the fund up and down rather than smiles. You can usually get really good lumber cutting 2×10s or even 2×12s. You will usually find some pretty fine lumber this way. The cost and waste is higher but you get a quality product.

-- Made in America, with American made tools....Shopsmith

View rwe2156's profile

rwe2156

2198 posts in 946 days


#12 posted 08-06-2016 11:33 AM

Ease up, NG. He’s a beginner asking questions. Obviously its not fine furniture if you read the post he said it was a farmhouse table.

bygrace,

Pipe clamps tightend that tight can cause a panel to bow. Counteract this tendency by alternating clamps over and under.

Another thing to look at is milling. What I do is lay out the top, draw a big triangle to keep the boards oriented, and alternate faces against the jointer fence. Any tendency for angles to be off will cancel out giving a perfect 90.

You don’t need to crank extremely tight. How tight? When the boards close up and the glue line appears, I turn it just a little more, that’s all. More than that, you’re going to cause a panel to bow the wider the worse.

With tables of this type with this type of lumber I suggest using an alignment method such as biscuits, dowels, or a spline. You could even tongue and groove.

Good luck hope you got your answer.

-- Everything is a prototype thats why its one of a kind!!

View GR8HUNTER's profile

GR8HUNTER

1145 posts in 178 days


#13 posted 08-06-2016 03:26 PM



Ease up, NG. He s a beginner asking questions. Obviously its not fine furniture if you read the post he said it was a farmhouse table.

bygrace,

Pipe clamps tightend that tight can cause a panel to bow. Counteract this tendency by alternating clamps over and under.

Another thing to look at is milling. What I do is lay out the top, draw a big triangle to keep the boards oriented, and alternate faces against the jointer fence. Any tendency for angles to be off will cancel out giving a perfect 90.

You don t need to crank extremely tight. How tight? When the boards close up and the glue line appears, I turn it just a little more, that s all. More than that, you re going to cause a panel to bow the wider the worse.

With tables of this type with this type of lumber I suggest using an alignment method such as biscuits, dowels, or a spline. You could even tongue and groove.

Good luck hope you got your answer.

- rwe2156

True that …... he knows what he says

-- Tony Reinholds,Pa. REMEMBER TO ALWAYS HAVE FUN

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bygrace

164 posts in 1434 days


#14 posted 08-06-2016 09:28 PM

jbay, ok, your right, How tight SHOULD I clamp.

jumbojack and rwe2156, thanks for your input. Some is good advice I’ve heard before but have forgotten, other is new to me so thank you very much!

-- Andy, Waxahachie, Tx.

View jbay's profile (online now)

jbay

816 posts in 364 days


#15 posted 08-06-2016 10:00 PM


jbay, ok, your right, How tight SHOULD I clamp.

jumbojack and rwe2156, thanks for your input. Some is good advice I ve heard before but have forgotten, other is new to me so thank you very much!

- bygrace

bygrace, I give the clamps a good snugging. Then, depending what it is, (a glue up) after about 15 minutes
I go around and give them another smidge.
I don’t try to tighten them with all my mite, just good and tight.
As also said clamp on top and on bottom. Even though your using cauls, with clamps only on one side your compressing the wood fiber more on that side. Best to use 2 clamps and compress the edge evenly

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

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