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Dowel size for slab joinery

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Forum topic by bhacksaw posted 05-26-2016 07:52 PM 495 views 0 times favorited 16 replies Add to Favorites Watch
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bhacksaw

161 posts in 1290 days


05-26-2016 07:52 PM

I have two 1 3/4” think walnut slabs roughly 12” x 8’-0” that i will be butt-joining with dowels. I’ve never done this before so I’m wondering what thickness dowels to use and spaced how far apart.I’ll be using a dowel-centering jig to keep the slabs level. Thanks!


16 replies so far

View BinghamtonEd's profile

BinghamtonEd

2281 posts in 1835 days


#1 posted 05-26-2016 09:09 PM

Sorry, no answer here, but…

Butt joint, as in you’re going to end up with a 16’ board?

-- - The mightiest oak in the forest is just a little nut that held its ground.

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bhacksaw

161 posts in 1290 days


#2 posted 05-26-2016 09:11 PM

No, it’s for a bar top so it’ll be joined along the 8 for edges.

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conifur

955 posts in 617 days


#3 posted 05-26-2016 09:28 PM

Typically the dowel diameter is 1/2 the thickness of the wood being jointed and as far how far apart I dont think there is a rule or a general rule, but for your length, I would say 12- TO 18 inches.

-- Knowledge and experience equals Wisdom, Michael Frankowski

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jbay

816 posts in 364 days


#4 posted 05-26-2016 09:34 PM

If I were making it I would use 2 rows of biscuits about 1/2” from the top and 1/2” from the bottom.
Approx. 4” from each end and probably 3 more equally spaced in between.

Dowels; 1/2” with the same spacing.

Lumberjock answer:
No biscuits or dowels, Today’s specially engineered glue is stronger than wood.
Make some cauls, glue and clamp putting clamps on top and bottom to insure even pressure from both sides.
And be sure to put some salt in the glue so the pieces don’t slide around when your clamping.

If you look at my projects you may want to disregard any of my information.

-- 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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bhacksaw

161 posts in 1290 days


#5 posted 05-26-2016 09:41 PM

Yes, today’s glue is stronger than wood. I’m sure we’ve all seen the youtube strength test videos. However, the joint always breaks right next to the glue. This is because the layer of wood (not sure if that’s the right term, I mean the continuous piece of wood that is between each grain line) has been made incomplete by the cut). I think it’s better to have that perpendicular support than to not have it, especially when dealing with a bar top that will have overhang.

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chiseler

121 posts in 354 days


#6 posted 05-26-2016 09:55 PM

Rule of thumb as what has already been said, 1/2 the thickness of material,otherwise 7/8”...BUT if you put a 1/4” continuos short grain spline 3/8” down from top,and 3/8”up from bottom,not only will it serve the same purpose as the dowels,it will be much stronger.It will add another 2” of glue surface to the thickness if you use 1/4” x 1”splines.

-- Scott.Triangle,NY Becareful and don't forget...They cut meat too!

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conifur

955 posts in 617 days


#7 posted 05-26-2016 10:22 PM



Rule of thumb as what has already been said, 1/2 the thickness of material,otherwise 7/8”...BUT if you put a 1/4” continuos short grain spline 3/8” down from top,and 3/8”up from bottom,not only will it serve the same purpose as the dowels,it will be much stronger.It will add another 2” of glue surface to the thickness if you use 1/4” x 1”splines.

- chiseler


Just remember the spline grain has to run perpendicular to the grain of the wood, and for your size pieces to cut the cut the spline that would take a high fence on a router table of table saw. I dont recommend it for your project.

-- Knowledge and experience equals Wisdom, Michael Frankowski

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jbay

816 posts in 364 days


#8 posted 05-26-2016 10:32 PM


Just remember the spline grain has to run perpendicular to the grain of the wood, and for your size pieces to cut the cut the spline that would take a high fence on a router table of table saw. I dont recommend it for your project.

- conifur

Why would he need a high fence? A simple slot cutter, hand held in a router would work fine.

-- 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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chiseler

121 posts in 354 days


#9 posted 05-26-2016 10:47 PM

correct about the perpendicular part. Use a router with a 1/4’ wing cutter to produce groove for the spline

Rule of thumb as what has already been said, 1/2 the thickness of material,otherwise 7/8”...BUT if you put a 1/4” continuos short grain spline 3/8” down from top,and 3/8”up from bottom,not only will it serve the same purpose as the dowels,it will be much stronger.It will add another 2” of glue surface to the thickness if you use 1/4” x 1”splines.

- chiseler

Just remember the spline grain has to run perpendicular to the grain of the wood, and for your size pieces to cut the cut the spline that would take a high fence on a router table of table saw. I dont recommend it for your project.

- conifur


-- Scott.Triangle,NY Becareful and don't forget...They cut meat too!

View bhacksaw's profile

bhacksaw

161 posts in 1290 days


#10 posted 05-27-2016 12:58 AM

I love the continuous spline idea! Thanks, guys.

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waho6o9

7174 posts in 2042 days


#11 posted 05-27-2016 03:37 AM

That is a good idea

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devann

2201 posts in 2158 days


#12 posted 05-27-2016 06:45 AM

+1 for the spline, that’s how I have tackled a similar situation. Only gluing one side of the spline. A table top, it worked.

But I have a dowel question. Do you glue both ends of the dowels?

I know when dealing with concrete slabs and dowels, one end has greased sleeves, allowing expansion. One end is secured into the concrete.

Does the same principle apply to wood slabs?

I’m guessing only glue one end of a dowel too?

-- Darrell, making more sawdust than I know what to do with

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Loren

8311 posts in 3113 days


#13 posted 05-27-2016 07:44 AM

For edge to edge joints, dowels every 8 inches or
so seem to do a pretty good job of every 2 of 3
dowels aligning the center one… so every 16”
you have a dowel in the middle.

It’s an assembly issue. Depending on your equipment
many woodworkers would say skip the dowels and
just use clamps and finesse to glue, then hand plane
the top. Dowels allow, for example, the alignment
of veneered surfaces, something I would be loathe
to trust biscuits to do as well.

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Tony_S

606 posts in 2548 days


#14 posted 05-27-2016 09:28 AM



However, the joint always breaks right next to the glue. This is because the layer of wood (not sure if that s the right term, I mean the continuous piece of wood that is between each grain line) has been made incomplete by the cut).
- bhacksaw

Interesting theory….never heard that one before.
If you’ve experienced cracking/splitting anywhere on your glued up panels or slabs before(glue joint or otherwise), it would be due to a poor glue joint(material prep), poor clamping technique, unstable material, or poor design. Nothing more.
Unless your trying to deal with an alignment issue in this instance, there shouldn’t be any need for dowels, biscuits or splines at all.
If it’s a comfort, or feelgood thing, then ‘have atter’, but any strength the dowels might add to a properly glued/clamped edge joint is so minimal, if any, it’s negligible.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

View BinghamtonEd's profile

BinghamtonEd

2281 posts in 1835 days


#15 posted 05-27-2016 11:44 AM


Yes, today s glue is stronger than wood. I m sure we ve all seen the youtube strength test videos. However, the joint always breaks right next to the glue. This is because the layer of wood (not sure if that s the right term, I mean the continuous piece of wood that is between each grain line) has been made incomplete by the cut). I think it s better to have that perpendicular support than to not have it, especially when dealing with a bar top that will have overhang.

- bhacksaw

This is just my opinion, but I think the design/construction of the top’s support is more important than using dowels or a spline to make the top. If the joint is part of the overhang, that’s a big enough overhang that it should be supported by something like corbels or steel brackets, and those would transfer the load off the top and down into the base structure. An overhang of that amount would mean that you have more top in the overhang than you have fastened to the bar cabinet. With 1 3/4 stock, that’s a lot of weight. If, on the other hand, the joint is over the bar’s cabinet structure, it should be well supported and fastened securely, and the joint becomes a non-issue. If a 1 3/4” thick, 8’ long bar top splits along that joint, or anywhere at all, it sounds like it was being used for much more than a bar top.

-- - The mightiest oak in the forest is just a little nut that held its ground.

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