LumberJocks

Murphy table, will the wood develop cracks?

  • Advertise with us

« back to Designing Woodworking Projects forum

Forum topic by Newbie17 posted 07-06-2019 04:59 PM 1301 views 0 times favorited 13 replies Add to Favorites Watch
View Newbie17's profile

Newbie17

169 posts in 1618 days


07-06-2019 04:59 PM

Topic tags/keywords: table project murphy pine splitting

I’m using this picture I found online to build a murphy table. From what I’ve read, I should be concerned about the boards under the table top that run perpendicular to the boards on the top. See illustration. I like the look of this murphy table, but will the table top split if I build it as shown? The wood is all pine. This is a free project for a business (long story short) and I don’t want it to make me look bad by self destructing. The table top is glued together already, but the boards for the underside support have not been attached yet. Also the table top is 48” long along the grain x 40” across the grain


13 replies so far

View Rich's profile

Rich

7091 posts in 1747 days


#1 posted 07-06-2019 05:13 PM

Use a fastener that allows the top to move. You can cut your own blocks with elongated screw holes or a tab that fits into a groove in the rail (the perpendicular piece). Also, there are commercial solutions like Figure-8s and Z-Clips.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View bondogaposis's profile

bondogaposis

6000 posts in 3509 days


#2 posted 07-06-2019 06:27 PM

It all depends on how you attach the top. If you allow for wood movement across the width of the top it will be fine. The easiest way to do it is to attach the top at the center with screws as you normally would. Then as you work your out wards from the center use a larger drill bit than the screw size for a pilot hole through the base, this works better you use pan head or washer head screws rather than flat head. That way the top will be able to move side ways in both directions while the center is secure.

-- Bondo Gaposis

View Newbie17's profile

Newbie17

169 posts in 1618 days


#3 posted 07-06-2019 07:39 PM

Your ideas gave me one.

What if I make the rectangular part (under the table top) as one piece using mortise and tenons and glue it only along the wood that is parallel to the table top? Then add a single screw in the center of the rails.

See the picture. The green rectangle would be one piece joined with mortise and tenon. The glue is only on the boards indicated and then the screw in only those two places.

Thoughts?

View Rich's profile

Rich

7091 posts in 1747 days


#4 posted 07-06-2019 08:58 PM


What if I make the rectangular part (under the table top) as one piece using mortise and tenons and glue it only along the wood that is parallel to the table top? Then add a single screw in the center of the rails.

- Newbie17

That will cause the top to split since those parallel pieces are fixed. If they floated it would be fine, but they don’t. However you attach it, you have to allow for the top to move relative to the frame it’s sitting on.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View bilyo's profile

bilyo

1376 posts in 2260 days


#5 posted 07-06-2019 10:28 PM

I’m assuming that the picture on the right represents how the table will look fully folded and that it will remain exposed as shown. If so, you may not want exposed screw heads, but you will need to allow for wood movement. You could achieve this by gluing the side pieces as you suggest. The cross pieces,, top and bottom would be “joined” to the side pieces with mortise and tenon or dowels, but without glue. Also, you should leave a small gap to allow for contraction of the top. Then glue the cross pieces to the top in only the center 3”. This will allow for cross grain movement of the top without having exposed screws. The trade-off, of course, is the small gap at the joint.
Another way to do the same thing is to have the top and bottom cross pieces run full width. Again, glued only in the center. The fully glued side pieces would again be joined with an unglued M&T to the cross pieces at the 4 corners. The difference is that the M&T joint could appear tight as the shoulder could fit tightly against the cross grain piece and any movement would be parallel to it.

View Newbie17's profile

Newbie17

169 posts in 1618 days


#6 posted 07-07-2019 02:15 AM

Bilyo, I’m going to do what you mentioned in the second paragraph. With the Festool Domino I have, this will be easy. The cross pieces will then have short dowels gluing them in the center to the table top, so no screw is exposed. Thank you all.

View bilyo's profile

bilyo

1376 posts in 2260 days


#7 posted 07-07-2019 03:14 AM

OK. Please let us know how it works out.
One more thing, if you do your assembly with the ends of the cross pieces aligned with the outside edges, over time and with changes in temp/humidity, you are likely to see some variation in that alignment. As the top expands or contracts, it will carry the glued-on long pieces with it. Because the cross pieces will not move, the ends will not stay in alignment. The change should be barely noticeable.
BTY, when you install your dominos, be sure to make the mortise slightly wider to allow for lateral movement.

View Lazyman's profile

Lazyman

7416 posts in 2545 days


#8 posted 07-07-2019 03:22 AM

Note that you have leave enough gap between the table top and the sides of wall cabinet as well. The top and bottom grain are similarly running across the table grain they will not move as much as the top does.

I assume that what you are planning is to make the loose tenon loose enough so that the the side pieces can move laterally as the table expands and contracts and only attach the end pieces with a single dowel in the middle? With no glue in the loose tenons, I am trying to think through what is holding the weight of the table when it is in the vertical position. For example, the top piece is not going to be attached to the sides so that a slight gap might be visible at that loose tenon joint which means that the leg may only be supported by the dowel when stored vertically. A slight torque could break the dowel or weaken the glue holding the dowel over time. I can imagine someone holding the leg when trying push the table up and slightly twisting the legs. I cannot quite wrap my mind around what will be going on at the bottom. What will prevent the bottom from pivoting on the dowel?

Just thinking out loud. It seems like too many things could go wrong.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View jdh122's profile

jdh122

1252 posts in 3975 days


#9 posted 07-07-2019 11:25 AM

I see no reason to build the frame on the bottom with mortise and tenon. I’d glue the two vertical pieces (the ones you have marked “glue” in your picture), then add the top and bottom pieces without joining them to the vertical piece, by screwing them to the tabletop in three spots, making sure that the two outside screws are in slotted holes. It would mean that there would be a small gap in the humid part of the year, but that’s the case even if you use dominoes or dowels.

-- Jeremy, in the Acadian forests

View Newbie17's profile

Newbie17

169 posts in 1618 days


#10 posted 10-16-2019 06:33 PM

Update:
If I were to do it over, I’d use thicker wood for the table top and add more horizontal boards against the wall for the pallet look. I was in a rush to finish TBH and since it was a pro bono project for an office, I was eager to move on to my own projects. Overall I’m OK with how it turned out.

View bilyo's profile

bilyo

1376 posts in 2260 days


#11 posted 10-17-2019 12:08 AM

That’s nice. Good job. I don’t think I have ever looked back on something I’ve done without wishing I had done something a little bit differently. That’s common. Thanks for sharing.

View Newbie17's profile

Newbie17

169 posts in 1618 days


#12 posted 09-10-2020 05:26 PM

Update: there has been zero wood splitting anywhere and it has held up well to lots of abuse from staff in the break room, so all is well. .

View bilyo's profile

bilyo

1376 posts in 2260 days


#13 posted 09-11-2020 05:09 PM

A testament to a job well done.

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com