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Adding stability to a trestle table

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Forum topic by LiveEdge posted 02-06-2014 10:59 PM 2229 views 0 times favorited 9 replies Add to Favorites Watch
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LiveEdge

486 posts in 1082 days


02-06-2014 10:59 PM

I’ve been working on a trestle table and been getting wonderful help from people on the site when I have questions. Currently I have noticed the table wiggles along the long axis a bit, especially when it has the leaves in (which aren’t actually done yet). I have a few ideas about how to add stability, but I wanted to run them by others to see what they think. I’ll try to include some pictures.

1) The top is not attached to the trestles yet. The top, extension slides, and 1×4 cross piece that sits on top of the trestle are not attached yet. Perhaps this, in itself, will add stability to the table lengthwise?

2) The cross pieces between trestles are not glued but rather wedged. I did this with the hopes that I could disassemble the table for moving. But perhaps I’m asking too much of a wedged tenon and mortise joint?

3) Of the four T&M joints, one is probably not too snug. I’m somewhat ashamed to show the joint here on the site with experts, but I’m really a novice. I could work on making the joint more snug (which would probably mean adjusting the joint above as well). Would that give me a lot of bang for my buck?

4) I could add another component that doesn’t exist in the table design I am copying. Would that be best?

Some pictures:




9 replies so far

View mahdee's profile

mahdee

3551 posts in 1230 days


#1 posted 02-07-2014 03:19 PM

You might consider gluing the “rails” and dovetail the cross sections. That way you still can disassemble for moving purposes.

-- earthartandfoods.com

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LiveEdge

486 posts in 1082 days


#2 posted 02-08-2014 03:46 AM

I’m starting to wonder if I’m expecting too much. Is it possible to make a trestle table rock solid in the long dimension? I think I will give up the idea of unglued cross-pieces. I put some clamps on the table to tighten those joints and that helped, but I can still get it to wiggle.

View Alster's profile

Alster

99 posts in 2676 days


#3 posted 02-08-2014 04:02 AM

It’s absolutely possible to get a trestle table to be rock-solid in the lengthwise dimension, even without glue. But it might take beefier wedges than you’re using. I’d be scared to hammer yours truly tight—there’s not a lot of long grain on the tenons, and your wedges, if tightened properly, will exert tremendous force.

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LiveEdge

486 posts in 1082 days


#4 posted 02-08-2014 06:07 AM

I hear that. One of the tenons was showing some cracking so I didn’t push it on the wedge. If I were to redo those cross pieces, how should I redo the through tenons?

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Alster

99 posts in 2676 days


#5 posted 02-09-2014 02:15 AM

To give you a frame of reference, do a google image search for “underhill spring pole lathe.” His lathe design has a structure very similar to your table’s, and, of course, it has to be rock steady. If you take a close look at the photos, you’ll find that sometimes he orients the wedges vertically, and sometimes horizontally. No matter which way the wedges are oriented, you’ll notice a good two to four inches of tenon past the wedge.

You might also look at the small trestle table in my projects: http://lumberjocks.com/projects/35970 . This table is very sturdy when the wedges are tapped tight.

I have a Stickley bookshelf with small through tenons like yours, and I can never drive them fully tight for the same reason you can’t drive yours tight—the tenons have cracks already and I don’t want to ruin them. I can get away with that on a small bookshelf. But a table gets much more abuse, and it needs to be strong. From what I can see of your table, it has beefy proportions, and I think you could get away with some longer tenons on the stretchers, appearance-wise.

One final note that you probably already know: The mortise for the wedge in your stretcher needs to be deep enough that when your wedges are driven up tight, the wedge bears on the surrounding wood and on the front of the mortise in your stretcher, but not on the rear of the mortise in your stretcher. If you’re hitting both ends of the mortise with your wedge, no amount of hammering will ever drive your joint up tight.

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LiveEdge

486 posts in 1082 days


#6 posted 02-09-2014 02:29 AM

I’m going to do the piece over and see what I get. I’ll add some to the heft of the tenon and do a better job making sure it’s flush on the other side of the joint.

One would think the splitting of the grain would come from spreading force vertically. I can’t quite visualize why the pressure of a wedge would do that. It seems like it would exert force horizontally.

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Alster

99 posts in 2676 days


#7 posted 02-09-2014 02:35 AM

It does exert force horizontally, but that can cause splitting, too. That’s why, if you mortise face frames by hand, it’s recommended to leave “horns” on your stiles that you will later cut off. The pressure of the wedge-shaped mortise chisel can blow out the end of the stile.

http://www.woodworking.com/ww/Article/Mortise-and-Tenon-Joints-7613.aspx

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LiveEdge

486 posts in 1082 days


#8 posted 02-11-2014 02:10 AM

I wound up cutting the lower piece again. I added an inch to the end of each tenon and wedged them nice and tight. The top tenons did both pop, but I glued the pieces back and wedged it while the clamp was on. I figured the glue actually adds strength to the joint. If it pops again it won’t be too hard to do that piece again as well.

The table is quite solid now. Thanks for the help. I’m almost done! Just have to add poly to the tabletop and add a few minor decorative pieces.

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Alster

99 posts in 2676 days


#9 posted 02-11-2014 02:15 AM

I’m glad it worked out, and be sure to post it when it’s done!

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