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Preventing warping and cupping when gluing up table tops, etc....?

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Forum topic by Anthony Finelli posted 12-16-2010 06:05 PM 20817 views 2 times favorited 7 replies Add to Favorites Watch
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Anthony Finelli

52 posts in 2242 days


12-16-2010 06:05 PM

Im looking to build a farm table for myself and a couple bar tables for friends and I was wondering if anything can be done to prevent cupping and warping when gluing up the table tops. The farm table is going to be made from barn board around 3/4 to 1 inch thick (have not bought the lumber yet, not quite sure on the thickness) and the bar tables from 2-3 inch thick stock. The last glue up I did was for my bookcase and when I glued up the top and bottems they cupped a bit (used dowels and 4 bar clamps). I was looking into buying a biscut jointer and using pipe clamps this time but is there something else I sould be doing…..use more clamps, build a jig like a veneer press? Im new to using dimentional lumber and am learning by doing and that can be expensive when buying barn board and 2-3” stock….If anyone can give me some pointers i would be very greatful!

-- Salem, New York "Find something you love to do and you will never have to work another day of your life"


7 replies so far

View IkeandBerry's profile

IkeandBerry

45 posts in 2726 days


#1 posted 12-16-2010 06:44 PM

I have made several large panels recently and have had really good success in preventing cupping/warping. I do not use biscuits or dowels for my panels. I join the boards on my joiner and then clamp the two boards together in my bench vise with the mating faces up and use my joiner plane to get them absolutely smooth. I then use pipe clamps set about one foot apart across the span. I do try to alternate the rings if it is flat sawn lumber. If is quarter sawn I do not worry about it as much. If the end grain on the panels is going to be exposed I will also sometimes use what is called a spring joint which causes more tension on the ends of the boards than the middle keeping the ends for splitting or cracking. Tommy Mac does a good job of explaining a spring joint on his website.

For the thicker stock I would make sure the mating surfaces are as smooth as possible and again use pipe clamps. I would also recommend using calls every few feet to keep the boards even while the glue is curing. You can just use flat scap pieces with some wax to keep the glue from sticking and clamp them to the top of the panels.

-- There is nothing like the sound of a hand plane passing across a board in an otherwise quiet shop.

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Kevin

462 posts in 2667 days


#2 posted 12-16-2010 07:09 PM

I don’t use biscuits or dowels either, just glue up boards. I usually try to use boards 3-4” wide and glue up 2 boards at a time. Once all those are done I’ll glue up 2 boards again (which is now around 6-8” wide). I use pipe or bar claps and make sure that I don’t put too much pressure on the boards. I also keep the f-bar claps around also to clamp to any ends or edges that are trying to rise or dip on me slightly.

Once that’s done i’ll take a small belt sander with a few quick passes to clean up any edges that aren’t exactly level, but it’s never anything major though.

A couple of links. I couldn’t find the free version from woodmagazine.com that shows the video of the guy gluing up a panel. His wasn’t the best anyway, but you got the idea.

http://www.fine-woodworking-for-your-home.com/glueduppanels.html
http://www.josephfusco.org/Articles/panel_glueups/Panel_Glue_Up.html
http://www.woodworking.org/WC/GArchive98/10_28smithglupan.html

-- Williamsburg, KY

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Kevin

462 posts in 2667 days


#3 posted 12-16-2010 07:15 PM

Pretty good video.
http://www.youtube.com/watch?v=o5DKRH7WMYs

I wait till the glue dries and take a paint scraper instead of taking a wet wag.

-- Williamsburg, KY

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Anthony Finelli

52 posts in 2242 days


#4 posted 12-16-2010 08:09 PM

thanks guys, I really appreciate it! Thank you kevin for the websites, they helped a great deal.

YOU CAN ALWAYS COUNT ON LJ’S!!!!

-- Salem, New York "Find something you love to do and you will never have to work another day of your life"

View Dan's profile

Dan

3630 posts in 2342 days


#5 posted 12-16-2010 10:07 PM

I don’t know if you can still buy them or not but I have some clamps that were designed for gluing up panels. The ones I have were made by ShopSmith and you place your boards in between two wooden bars and when you tighten the clamp it pulls the boards together as well as apply downward pressure to help prevent cupping. I don’t think I have seen another company market these so you would have to look into it. They work rather well.

-- Dan - "Collector of Hand Planes"

View Kevin's profile

Kevin

462 posts in 2667 days


#6 posted 12-16-2010 10:13 PM

Anytime Anthony, glad they helped you out. It’s always easier for me when I see someone do it too.

Kevin

-- Williamsburg, KY

View dbray45's profile

dbray45

3178 posts in 2238 days


#7 posted 12-17-2010 03:49 PM

A couple rules that I live by—
If the the boards are quarter sawn, they will not cup – split, yes, cup no
If the boards are not quarter sawn, the wider the board the more chance to cup – one of the reasons that the big companies use small strips because there is so much less waste and no opportunity to cup.

If you are using wide boards, choose them carefully and make sure they are dry before you mill them. Cupping happens when the boards dry unevenly, so I am told. How they are cut off the tree make can all the difference.

-- David in Damascus, MD

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