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round table apron

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Forum topic by robc posted 03-24-2013 07:43 PM 2018 views 0 times favorited 8 replies Add to Favorites Watch
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robc

22 posts in 1732 days


03-24-2013 07:43 PM

Topic tags/keywords: table bending apron jig question trick maple shaping

I need to build a round table apron. The size of the table is 48 inch so I figure the apron would be 46 inch. I plan to use glued lamination but have a question. I read a post about making the form to account for the defection of the apron after it is removed from the form. Is this something that I really need to worry about.

I plan to make each half longer than I needed. This is the first time I have tried a wood bending project.


8 replies so far

View Fred Hargis's profile

Fred Hargis

1887 posts in 1181 days


#1 posted 03-24-2013 08:13 PM

It can be enough to make adjustments needed. I’d do the lamination first, and go from there. Using an urea formaldehyde glue seems to em to reduce the spring back slightly (compared to PVA), but there will still be some. The thing is, the spring back will be at the ends so your piece won’t be a perfect circle. Depending on how you fasten it to the table, you might be able to force it back to what you want…but I’d still do them first and see what you get. At least that’s the way I’ve done it.

-- Our village hasn't lost it's idiot, he was elected to congress.

View 404 - Not Found's profile

404 - Not Found

2544 posts in 1657 days


#2 posted 03-24-2013 09:45 PM

At the size you are proposing the piece will be flexible enough to put back into shape even if there is a bit of deflection. Just make sure it is well glued, tightly clamped and left to dry properly before taking it out of the form.

View Lee Barker's profile

Lee Barker

2169 posts in 1538 days


#3 posted 03-24-2013 11:01 PM

Is the top solid stock? Does it open for leaves?

I would say definitely make your form to include some springback. The less stress on the piece, the better. If the top does not open for leaves, you’ll be making a circle of your two glueups and it will be easier to force it out and attach it than the reverse.

I would make the pieces 8” longer than the goal so you have 4” each end to work with to get everything snug in the form.

In the days of making oak tables, I’d glue up alder laminates with just oak on the outside. It was easier to bend and worked just fine.

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"

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shipwright

5085 posts in 1486 days


#4 posted 03-25-2013 12:10 AM

Hide glue will just about eliminate spring back and doesn’t require the clamping pressure that UF does. It would be to long an open time for hot hide glue but a perfect job for Old Brown Glue or another liquid hide glue.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View RogerInColorado's profile

RogerInColorado

294 posts in 642 days


#5 posted 03-25-2013 01:07 AM

I completed one in Alder in December. Mine had a 53 inch radius and I concluded that making the lamination in two pieces would limit my ability to adjust or manipulate for spring back to only two joints and therefore my correction options. I decided to make the apron in three pieces and, as Lee said above, made each longer by about 8 inches. This made the form easier to build and manipulate because the arc was less than a half circle. Before I made the first of the three arcs, I drew my lines on the form to show the location of the cut (and therefore the angle) so could mark the pieces before they were taken from the form and did their spring back trick.

Before I did the glue up I soaked the Alder overnight (shorter might have worked ok, too, but I wasn’t in a hurry) in a 7 foot length of 4” PVC pipe. Then I put the pieces in the form in the order I wanted them to be in the glue up and let them “dry” there over night (still not in a hurry) and started the soak for the next batch. Letting them “dry” without glue made the final assembly with glue much less stressful because they were already “trained”.

I did the glue up using urethane for two reasons: long working time and all the moisture still in the wood even after overnight in the form. I let the glue up sit overnight and when I released the form and pried the parts loose (after marking the cut) my spring back amounted to between 1/8 and less than 1/4 inch total, way easy to manipulate with clamps while mounting to the table. As a note, I drew my positioning circle on the bottom of the table as a guide for positioning the arcs during assembly.

View NGK's profile

NGK

93 posts in 599 days


#6 posted 03-26-2013 03:52 AM

The boys above have pretty well covered the waterfront and stolen all my ideas. With radii that large, you can avoid the “wet soak” and steaming by making thin laminate pieces. Many folks don’t know that Elmer’s white glue is often as good or better than the so-called yellow Woodworker’s Glue and a heckuva lot cheaper AND had longer open time. Marc Adams was hired to do some research on various glues and states that the yellow stuff including TiteBond I is designed for carpenters and construction crews for lumber in outdoor conditions—mostly about 15 percent moisture. Furniture construction, by contrast, is usually wood of 6- to 9-percent moisture. And white glue has a longer “open” time and dries clear.

Regarding the table top problem above, I, too, considered constructing the apron in three parts. Join them with splines or use butt joints with a short extra section of the “curve” as an inner splice. Actually, if you’re making the table from scratch and you make the round top a little extra thick you can get by with NO apron, as I did for a pedestal-type table for a law firm. Keeps everything 3-4 inches lower. They liked the first one well enough to place an order for the second one.

View robc's profile

robc

22 posts in 1732 days


#7 posted 03-26-2013 12:46 PM

The table has no leaves. This may sound like a stupid question but does the apron give support the outside edge of the table. Again I have been woodworking for about 3 years now and have no formula training…just what I read and watch on instructional videos.

I ask because I was planning on support “arms” coming out from the middle to support the end. The out side edge is flimsy. Does the apron support that area or do you still need the “arms”. I am not working from plans other than the shop drawings.

The problem with the apron is the jig and construction.

View DustyMark's profile

DustyMark

271 posts in 758 days


#8 posted 03-29-2013 01:12 AM

I built a 48” diameter table that opened for a leaf. So, I built the apron in two pieces. Spring back was negligible using reisncorcal glue (no longer available as far as I can tell.) One thing to consider is the amount of expansion and contraction across the grain with humidity changes if you fasten the two ends to each other. A solid top round table is on my to-do list and I’ll probably tackle that in 2014.

-- Mark, Minnesota

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