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Which would be stronger?

by AwlThat
posted 12-04-2018 05:27 PM


6 replies so far

View HokieKen's profile (online now)

HokieKen

11599 posts in 1702 days


#1 posted 12-04-2018 05:38 PM

Yes. The way they did it, the weight of the table + whatever is on it is all carried in shear. Using a half lap puts the load in compression on the legs. The compressive strength of wood (and any other material I can think of) is much higher than it’s shear strength.

On the other hand, It also depends on how they attached the 2×6 ledges. If they were through bolted for instance, the load is carried by the bolts in shear which is stronger than the wood. If they glued them, the load is carried in shear at the glue joint. Screws? The load is carried partially by the screws in shear and partially by the wood in compression.

So, basically, it just depends. IMO, the best bet would be half-laps.

-- Kenny, SW VA, Go Hokies!!!

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AwlThat

49 posts in 650 days


#2 posted 12-04-2018 05:49 PM

I looked at the video again and the blocks were actually used as a stop to position the frames within the four legs. The 2×6 legs are actually screwed into the outside corners of the frames with 5 screws. I was thinking the blocks were left on for more support.

Here’s a link to the video. It’s a Jay Bates build. The point of interest is about 1:30 into the video.

I’m certainly not questioning his work, I’m just curious about the difference in strength of the joinery and even whether half-laps are overkill for this particular application.

https://www.youtube.com/watch?v=rPvkdU5kkqA

View HokieKen's profile (online now)

HokieKen

11599 posts in 1702 days


#3 posted 12-04-2018 05:56 PM

Yeah it’s plenty strong enough with 5 screws in each corner. 1/2 lap would still be the stronger joint but sometimes the time to make the joint doesn’t justify the overkill ;-)

-- Kenny, SW VA, Go Hokies!!!

View EarlS's profile

EarlS

3316 posts in 2912 days


#4 posted 12-04-2018 05:56 PM

The bigger question is “what do you intend to put on the table? While half laps may carry a lot more weight, do you really need something that strong? Of course, if you like the look of half laps, or Mortise and tenon, or whatever joint you like, then build that.

Personally, I like the joinery to be functional and appealing to look at. Otherwise, you could just get a Kreg Pocket hole jig.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

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AwlThat

49 posts in 650 days


#5 posted 12-04-2018 06:06 PM

Thanks, Ken and Earl. Really appreciate the good words.

To your point, Earl, about the appearance, I think I would like the flat surface all the way around rather than the legs sticking out at the corners. Of course, this particular table was going to have a torsion box on top so there would be no functional disadvantage of Jay’s choice of leg joinery, whereas if the table top was just going to be plywood on top of the frame, having a flush surface all the way around might be more desirable.

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EarlS

3316 posts in 2912 days


#6 posted 12-04-2018 09:34 PM

I can’t say that I’ve seen anyone on LJ admit to under building an outfeed/assembly table. Or maybe the better way to state it: No one will ever admit to building an under strength outfeed table and having it collapse.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

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