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Farm table Q's: end-to-end and breadboard joints

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Forum topic by barnwood14 posted 01-18-2017 03:25 PM 1248 views 0 times favorited 6 replies Add to Favorites Watch
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barnwood14

3 posts in 336 days


01-18-2017 03:25 PM

Topic tags/keywords: breadboard end table joining end to end mortise and tenon farm table

Hello folks. My first post after a long time using this site as a resource. Y’all have been an incredibly valuable tool for newbies like me on a few projects in the last year, so thanks for all the input!!

Before anyone yells at me, I know there are dozens of posts on this topic and I feel like I’ve read them all, but I still wanted to run a few ideas on an upcoming project before I dig in.

Here’s the deal: mom had a dead oak tree taken down from my great-grandfather’s place, and milled into 6’ 2×4s and 4×4 lumber. Kiln dried. Nothing wider than 4”. This is special ‘family heirloom’ sentimental value wood, so she asked me to make a farm table out of it, 7’x3’ (approx). (See attached pic of the lumber… not stacked properly and in the cellar… ugh… but once I get it up here next week I’ll make sure it didn’t get moist while it was sitting there for a month. Ignore top moldy pieces, those are scrap).

Design: Since she wants it 7’ minimum and wood isn’t longer than 6’, I’m going to lay out (2) 2×4s per length to make 6’6” (off set so end-to-end joins don’t line up with the boards next to it). It’ll take (9) 2×4s edge-to-edge to make 3’ width. Then 2×4 breadboard ends.

I want it STRONG. She has grandkids, and I don’t want to make anything delicate… I want it USED. I’ll finish it properly so it can take a beating, but kids leaning on ends (or sitting on it, you know how kids are) and plenty of strength through the length.

Joint plan!
Breadboard end: This is the big question. Damn these things…. First time I’ve done em. (well, I did on my first table 15yrs ago and after 5yrs in my house gave to my sister in NC, and 6mo later cracks all over… I had glued it up solid b/c I had no idea wtf I was doing ha!). I’d prefer to go mortise on breadboard, b/c it’s only 4”, & tenon on table top, but wondering if I need 2” wide tenon on each and every 2×4? I’m worried about wood movement/cracking, and planning to allow for that but wondering if the more tenons the more possibility of error and cracking?
Also, I prefer to dowel the tenons from underneath so can’t see the plug/hole at top. That’ll work, right?
SUGGESTIONS WELCOME!!

Edge-to-edge: Simply glueing. Dowels, biscuits etc. don’t seem necessary to me. SEEM RIGHT? With (9) 2×4s edge-to-edge wondering if that changes things.

End-to-end: For the 2 pieces connecting length-wise, I’m thinking 1/2 lap. That necessary? Dowels don’t seem necessary b/c I’m also getting support from surrounding edge-to-edge, so why go to trouble, but just glue doesn’t seem like enough. Plus, the pieces won’t be less than 2 or 3’. Don’t want picket-fence top. Just 2 pieces per length. Also, I’m not a fan of finger-joint look on top.

Apron: Apron/legs will go pretty close to edges for support, attached with Rockler table top fasteners for wood humidity movement (http://www.rockler.com/table-top-fasteners?SSAID=389818). I’d rather not use these metal fasteners, but again… I have visions of that cracked table and I do NOT want that happening again.
Do I need a center piece in middle (going side to side) to support middle of 7’ table? Which is also glued/joined to apron, and fastened to top with same fasteners for wood movement.

I have a table saw, router (no router table), power planer for face of boards, and hand jointer plane for edges.

That’s about it folks. Long post, but I want to get all the details so you don’t need to ask a ton of questions!

Thanks and keep up the great work!

Brian.

-- "Making is thinking."


6 replies so far

View JBrow's profile

JBrow

1274 posts in 757 days


#1 posted 01-21-2017 04:24 AM

barnwood14,

Breadboard end. I am not convinced that the breadboard ends will add much strength to the top; at 1-1/2” or 2” thick, the top should be plenty strong. If the wood is dry and acclimated and all six surfaces are finished, and the top is free to expand and contract, wood movement and associated problems are likely to be minimal.

If the breadboards are a design element, 9 mortise and tenons (1 per 4” wide board) sounds excessive. Three or four deep mortises and corresponding long tenons seem enough to me. A groove along the entire length of the end board and a corresponding tongue milled on the ends of the top would provide continuous support of the breadboard end. The tenons would extend out further from the tongue. Ensuring the tenons are cut narrow enough would leave room in the mortises for expansion and contraction of the top.

I see no reason why the dowel could not be installed on the underside of the top. After the holes for the dowels are drilled, the breadboard can be removed and the holes in the tenons elongated to allow the top to expand and contract. The dowels should only be glued to the breadboard. The dowel setting in the slot in the tenon should be glue-free; otherwise the top could not expand or contract. One of the tenons near the center of the top could be glued in place. Since no other tenons are glued and the tongue and groove is glue-free and the tenons in the top are slotted, the top should be free to expand and contract outward toward the edges from the center.

Edge-to-edge. Gluing the top edge to edge as you described sounds ok to me. If the edges are properly jointed and the butting surfaces are kept as flush as possible along the entire length of the top during glue-up, the top could be flushed up with minimal effort. It is probably a good idea to glue the top a few boards at a time. There will be a lot of glue to spread and if PVA wood glue is used, it can skim over before glue is applied to the third or fourth boards and yield weak joints.

End-to-end. Making long boards from shorter boards could be a challenge. Applying clamping pressure to the ends of the board could introduce a bow along the length. A simple butt joint would be weak. Lengthening the shorter boards while gluing the top together would complicate the glue-up, since clamps running across the width of the glue-up would get in the way of clamps pulling the ends of the boards together. Keeping the entire glue-up flat could be difficult.

Since end-grain butt joints are weak, using a half-lap joint or a spline to splice ends together are a good ways to go to produce long boards from shorter ones. The half lap will be visible on the edges of the top, whereas the spline could be hidden, although the butt joint line would be visible.

Another, simpler option would be to glue-up three or more shorter table tops. The shorter tops could be joined to get the length you would like. The top would have the appearance of a table with an expansion leaf, but in this project the center leaf could be permanently jointed with a half lap, splines, or dowels.

Not only is the three or more shorter top option a simpler approach, but it also offers the opportunity for some artist expression. For example (there are other patterns that could be used), the outer sections could be cut to a rectangle so that the glued planks run at a 45 degree angle to the center leaf and the long edges of the table. The center leaf could be cut so that the glued-up planks run parallel to the long edges of the table. A top that features these types of design can offer some construction challenges for dealing with movement.

Apron. The metal Rockler clips would be fine; as would figure 8 fasteners, shop made clips, or cleats running from long rail to long rail and with several slots cut along the length of the cleats to accept screws that secure the top. All of these methods allow the top expand and contract with the fastener attached to the top. No glue anywhere when attaching the top to the base will go a long way in preventing the top from cracking.

Adding a center support between the long aprons would strengthen the table base. But with a 7’ long table, I would probably add two (rather than one) center supports. Adding table top fasteners to center support rail(s) is probably unnecessary but if I were building this table, I would add them anyway.

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barnwood14

3 posts in 336 days


#2 posted 01-26-2017 07:00 PM

JBrow thanks so much for the reply! I was beginning to think after nearly a hundred views but no replies I either had a dumb question or something. Super-helpful answers, thanks so much. Quick follow-up questions:

Re: bb ends: the 4 tenons you suggest… they should be made from separate boards, correct? Like, don’t make a 4” tenon across the edge-joints (taking 2” of board #1 and 2” of board #2 next to it). Is that more stable somehow? Or would defeat the purpose of allowing that wood to expand?

I’ve been reading books on the tongue, elongating holes for movement etc. so feeling good about how to do that part.

Might not mill the top, to keep it rustic. So, only milling bottom & sides, with a light sand on top. That an issue? Will make sure all pieces are milled flat so won’t be wavy on top.

Re: end-to-end, I think lap joints are the way to go. I could do dowels but I would like to try something at least a little different. Then they’ll all be supported by width-glue-up. Agree I should make the longer boards first then clamp up the width.
My mom was pretty specific on style—I do a lot of angled/design barnwood table tops and she said that’s not her thing (ouch! ;) so going with classic look.

Great advice on double-support apron.

Thanks again!


barnwood14,

Breadboard end. I am not convinced that the breadboard ends will add much strength to the top; at 1-1/2” or 2” thick, the top should be plenty strong. If the wood is dry and acclimated and all six surfaces are finished, and the top is free to expand and contract, wood movement and associated problems are likely to be minimal.

If the breadboards are a design element, 9 mortise and tenons (1 per 4” wide board) sounds excessive. Three or four deep mortises and corresponding long tenons seem enough to me. A groove along the entire length of the end board and a corresponding tongue milled on the ends of the top would provide continuous support of the breadboard end. The tenons would extend out further from the tongue. Ensuring the tenons are cut narrow enough would leave room in the mortises for expansion and contraction of the top.

I see no reason why the dowel could not be installed on the underside of the top. After the holes for the dowels are drilled, the breadboard can be removed and the holes in the tenons elongated to allow the top to expand and contract. The dowels should only be glued to the breadboard. The dowel setting in the slot in the tenon should be glue-free; otherwise the top could not expand or contract. One of the tenons near the center of the top could be glued in place. Since no other tenons are glued and the tongue and groove is glue-free and the tenons in the top are slotted, the top should be free to expand and contract outward toward the edges from the center.

Edge-to-edge. Gluing the top edge to edge as you described sounds ok to me. If the edges are properly jointed and the butting surfaces are kept as flush as possible along the entire length of the top during glue-up, the top could be flushed up with minimal effort. It is probably a good idea to glue the top a few boards at a time. There will be a lot of glue to spread and if PVA wood glue is used, it can skim over before glue is applied to the third or fourth boards and yield weak joints.

End-to-end. Making long boards from shorter boards could be a challenge. Applying clamping pressure to the ends of the board could introduce a bow along the length. A simple butt joint would be weak. Lengthening the shorter boards while gluing the top together would complicate the glue-up, since clamps running across the width of the glue-up would get in the way of clamps pulling the ends of the boards together. Keeping the entire glue-up flat could be difficult.

Since end-grain butt joints are weak, using a half-lap joint or a spline to splice ends together are a good ways to go to produce long boards from shorter ones. The half lap will be visible on the edges of the top, whereas the spline could be hidden, although the butt joint line would be visible.

Another, simpler option would be to glue-up three or more shorter table tops. The shorter tops could be joined to get the length you would like. The top would have the appearance of a table with an expansion leaf, but in this project the center leaf could be permanently jointed with a half lap, splines, or dowels.

Not only is the three or more shorter top option a simpler approach, but it also offers the opportunity for some artist expression. For example (there are other patterns that could be used), the outer sections could be cut to a rectangle so that the glued planks run at a 45 degree angle to the center leaf and the long edges of the table. The center leaf could be cut so that the glued-up planks run parallel to the long edges of the table. A top that features these types of design can offer some construction challenges for dealing with movement.

Apron. The metal Rockler clips would be fine; as would figure 8 fasteners, shop made clips, or cleats running from long rail to long rail and with several slots cut along the length of the cleats to accept screws that secure the top. All of these methods allow the top expand and contract with the fastener attached to the top. No glue anywhere when attaching the top to the base will go a long way in preventing the top from cracking.

Adding a center support between the long aprons would strengthen the table base. But with a 7’ long table, I would probably add two (rather than one) center supports. Adding table top fasteners to center support rail(s) is probably unnecessary but if I were building this table, I would add them anyway.

- JBrow


-- "Making is thinking."

View JBrow's profile

JBrow

1274 posts in 757 days


#3 posted 01-27-2017 03:18 AM

barnwood14,

It is hard to say why you received no response, but I doubt it has anything to do with the merit of your questions. I try to troll the Unanswered questions for those where I might have something helpful to say. I am glad you found my reply of some value.

bb ends: the 4 tenons you suggest… they should be made from separate boards, correct? Is that more stable somehow? Or would defeat the purpose of allowing that wood to expand?

Striving to ensure the tenons do not incorporate a glue-line could avoid the tenon weakening in the unlikely event that the joint fails. But if not possible and a good glue-up of the top is achieved, a tenon with an incorporated glue-line would probably be fine.

Whether a glue-line occurs within a tenon would have no effect of the wood movement. Wood movement is allowed so long as the tongue and groove is not glued (except for 2”-3” at the width-wise center), the tenon is not glued in the mortise, the mortise is wide enough to allow tenon to move within the mortise, and the dowel in elongated hole in the tenon are not glued to the tenon.

Might not mill the top, to keep it rustic. So, only milling bottom & sides, with a light sand on top. That an issue? Will make sure all pieces are milled flat so won’t be wavy on top.

The only potential issues I see with your milling plan for the lumber making up the top (flattening the bottom face and straightening the edges) are that newly exposed wood on the bottom surface could give up or take on moisture to a greater degree than the upper un-planed surface. Proceeding immediately to glue-up after milling and then getting a film finish on all surfaces and exposed edges of the top as soon as possible could help reduce or avoid lumber twisting after milling (but I am not sure how much of a problem this would actually be).

The second issue could be that the upper surface may not be flush and allow dinner plates to rock and drinking glasses to set unevenly on the upper surface. But if your Mom wants a more classic and refined look, you may be milling all four surface of the lumber used to make the top.

Re: end-to-end, I think lap joints are the way to go. I could do dowels but I would like to try something at least a little different.

Since you mentioned dowels, pinning the half-lap with a dowel or two installed from underneath could further strengthen the half-lap joint. It could be a through dowel or it could be buried half-lap part of the tongue that is part of the upper surface of the top.

View Rick_M's profile

Rick_M

10628 posts in 2217 days


#4 posted 01-27-2017 08:10 AM

I’m too tired to read and process all this right now but I’m guessing you didn’t get an answer right away because it’s a wall of text with a lot of extraneous information to process. Usually best to skip the story and go right to your plan and questions. I’ll try to take a 2nd look tomorrow and see if I have anything to add but Jbrow probably has you covered.

-- http://thewoodknack.blogspot.com/

View barnwood14's profile

barnwood14

3 posts in 336 days


#5 posted 01-27-2017 02:35 PM

I always see vague posts so was going for detail, bc details matter on execution decisions. But all set with Jbrow thanks Rick.


I m too tired to read and process all this right now but I m guessing you didn t get an answer right away because it s a wall of text with a lot of extraneous information to process. Usually best to skip the story and go right to your plan and questions. I ll try to take a 2nd look tomorrow and see if I have anything to add but Jbrow probably has you covered.

- Rick M


-- "Making is thinking."

View Rick_M's profile

Rick_M

10628 posts in 2217 days


#6 posted 01-27-2017 05:57 PM

I would not do lap joints for end to end, scarf or finger joints would be correct, no pinning necessary. With a lap, any imperfection is going to show and leave a gap.

-- http://thewoodknack.blogspot.com/

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