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Proper number of dowels?

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Forum topic by Hmlee posted 05-10-2013 04:58 PM 1018 views 0 times favorited 5 replies Add to Favorites Watch
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Hmlee

16 posts in 577 days


05-10-2013 04:58 PM

Hi all. I’m beginning work on a dining table glue-up using 8/4 ash. The glue-up consists of 3 boards, two outer boards 11.75” wide and a middle board 6” wide. I was planning on using dowels for the joining, but I’m wondering how far apart the dowels should be. The total table length is 5 feet. I’ve never worked with 8/4 wood before, and I want to make sure I make a strong joint but don’t waste materials…


5 replies so far

View rockindavan's profile

rockindavan

283 posts in 1289 days


#1 posted 05-10-2013 05:19 PM

How many dowels do you need to ensure the joint is strong?...None. A edge joint is plenty strong on its own, and dowels will only help with alignment. 3 or 4 along the length should be good enough to keep everything aligned.

View Lee Barker's profile

Lee Barker

2163 posts in 1503 days


#2 posted 05-10-2013 08:25 PM

Unless your dowel drilling is dead on, the dowels only make alignment worse, not better. If you do the glueup in two stages, so you’re just dealing with one 5’ joint at a time, you’ll be able to walk and tap as you clamp and get it amazingly close.

There are those who will recommend that you rip the 11.5 pieces in two and flop half of them to minimize cupping. I suggest you give this serious consideration. More glue joints, yes, but visually a more interesting top and definitely more likely to stay flat.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View realcowtown_eric's profile

realcowtown_eric

300 posts in 589 days


#3 posted 07-04-2013 06:37 AM

Concur with both previous posts. Dowels joining 8/4 ash are a totally unneccesary complication that will only add frustration. They will not, could not add any structural integrity, nor add any possible benifet to the glue up.
Not just a total waste of time, but possibly a detracting outcome. Please park this idea.

I’d be more worried about using boards 11” wide, particularly with ash.

If you look at the ends and see the annular rings. well, they tend to want to go linear and straighten out, and that’s what they will do. Ash seems to me to react particularly promptly to moisture changes. a an 11” wide board is not just gonna move a little, but perhaps a whole lot.

And do watch you allow for wood movement when you attach the top to the base, cause ash splits real good and easy!

Conventional wisdom is to alternate grain direction….cup up, cup down,cup up, cup down, etc and with much smaller widths of wood than you propose. so that the fluctuations in ambient moisture do not coalesce in the same direction, but rather are somewhat distributed and their effects moderated. Something to think about.

just my thoughts.

Eric

-- Real_cowtown_eric

View bondogaposis's profile

bondogaposis

2528 posts in 1004 days


#4 posted 07-04-2013 12:06 PM

Zero dowels is the way to go. Glue alone is the best joint for edge to edge, especially w/ 8/4. Dowels unless they are in absolutely perfect alignment, something that is very difficult to accomplish, will actually prevent good edge to edge contact and add almost nothing to the strength of the joint. Using modern glues will give a bond that is stronger than the wood itself in an edge to edge application.

-- Bondo Gaposis

View Don W's profile

Don W

15029 posts in 1220 days


#5 posted 07-04-2013 12:25 PM

+1, no need for dowels.

8/4 ash for a table top? Nice choice. Post some pic’s back here.

-- Master hand plane hoarder. - http://timetestedtools.com

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