grain direction

[engineer one]

ok so after all the help, i have completed the end panel flattening, and am working my way through getting the legs square and equal.

next thought process. i want to m/t the legs into the top with the ends of the mortices being visible, and wedge. i understand i need to put the wedges across the grain of the top. and in principal across the grain of the legs. but here is the rub.

how do you determine the grain direction at the top?? :roll:

obviously i have to chose the best grain direction for the legs themselves, and they are pretty straight grained bits of oak. but then what????? :?

paul :wink:

 

[engineer one]

ok so you all think i am being a little dumb, but stick with it.

since my "legs" are made of "offies", i e not specifically chosen, they have different grain patterns on the top. :?

two are easy since i can see the grain going across one side to another.
however, two have a more curved grain pattern across it. hence my question with a pattern like that, how do you decide the best way to place the wedges?

obviously also part of this is since it is oak, i want to arrange the legs so that there is a decent grain direction when you look at it. i am either going to have wildish grain showing, or straight, and to an extent the top layout will affect this too.

so any help would be appreciated :roll:

paul :wink:

 

[Lord Nibbo]

I'm not to sure exactly what your getting at, if I understand correctly it's not the grain of the leg that matters, it the direction of the grain of the top thats the deciding factor, the wedge wants to cross the grain as in this pic

Thats how I would place the wedge.

 

[engineer one]

thanks mate, you are suggesting what i have in mind, i was just i guess wondering whether in fact the end grain of the leg wood makes any difference to the wedge placement??? :roll:

or the way round in which you place the leg??

paul :wink:

 

[woodbloke]

I'm not to sure exactly what your getting at, if I understand correctly it's not the grain of the leg that matters, it the direction of the grain of the top thats the deciding factor, the wedge wants to cross the grain as in this pic

Thats how I would place the wedge.

Sorry LN, in a table top as indicated in your pic, the wedge needs to go the other way ie. turned thru' 90deg. As you have it in your pic there will be little strength as the leg is being wedged against the end grain of the top. For the strongest joint in this type of situation you need to glue long grain to long grain which is what happens if you turn the wedge thru' 90deg. In addition there is a danger of splitting out the little bit of the table top as it's short grain if you wallop in the wedge as shown - Rob

 

[Lord Nibbo]

Sorry LN, in a table top as indicated in your pic, the wedge needs to go the other way ie. turned thru' 90deg. As you have it in your pic there will be little strength as the leg is being wedged against the end grain of the top. For the strongest joint in this type of situation you need to glue long grain to long grain which is what happens if you turn the wedge thru' 90deg. In addition there is a danger of splitting out the little bit of the table top as it's short grain if you wallop in the wedge as shown - Rob

I understand what your saying but thats only how I've drawn it, with more overhang it's not as big a problem as splitting the top if you did it how you say to do. :wink:

 

[woodbloke]

Agreed, with more overhang the problem doesn't exist but the main feature of wedging a top like this is to glue long grain to long grain which will only happen if the wedge if turned thru' 90deg - Rob

 

[engineer one]

well woodbloke, that's different from what i had thought i had heard.
:?
paul :wink:

 

[woodbloke]

well woodbloke, that's different from what i had thought i had heard.
:?
paul :wink:

Paul - in a top as His Lordship has drawn it, which I assume is how you are doing yours, the wedge needs to be parallel to the grain in the table top so that the joint is between long grain and long grain rather than long grain (leg) to end grain (table top)....clear as mud, I 'spect - Rob

 

[engineer one]

could have sworn that i saw something in gww that contradicted it,
which is why i asked the question :roll: :?

paul :wink:

 

[Philly]

Hang on - isn't the wedge correct in the picture? The wedge has to press against end grain - turn it 90 degrees and it will split the top when you hammer the wedge in.
Clouding the waters.....
Philly

 

[engineer one]

there you go philly that is what i was sure i had heard :? :roll:

confused you will be :twisted:

paul :wink:

 

[dchenard]

Hang on - isn't the wedge correct in the picture? The wedge has to press against end grain - turn it 90 degrees and it will split the top when you hammer the wedge in.
Clouding the waters.....
Philly

Second Philly here.

Take a board and drive in a chisel 1" from the end. What will happen if the chisel is driven perpendicular to the grain? Nothing. Drive the same chisel in line with the long grain, and the board will split, as if hit by an axe.

Unless located very very close to the end of the tabletop, LN's drawing is correct IMHO. Whether such a joint is desirable in a solid top table, that's another issue...

DC

 

[engineer one]

dc like your words, but thenthe question.

why does one do certain joints? because it is aesthetically pleasing.

the table is quite low, say 600 high, and about 800 long by 600 wide, and will have a storage facility underneath which will i think keep the legs stable.

otherwise i would put the legs on underneath with what????

i just figured it would look nice, and be an effective way of keeping the legs square and stable in their shape. :twisted:

paul :wink:

 

[Lord Nibbo]

Thank you Philly and dchenard for confirming my way is the way you would both do it. It may not look as aesthetic but it's got to be the strongest way. Just imagine doing a square through mortice half way up a leg to fit a rail, the way I explained across the grain to fit a wedge would do no harm, do it with the grain and you will split the leg. Anyway I'm not going to argue about it everyone to their own :lol: :wink:

 

[dchenard]

dc like your words, but thenthe question.

why does one do certain joints? because it is aesthetically pleasing.

the table is quite low, say 600 high, and about 800 long by 600 wide, and will have a storage facility underneath which will i think keep the legs stable.

otherwise i would put the legs on underneath with what????

i just figured it would look nice, and be an effective way of keeping the legs square and stable in their shape. :twisted:

paul :wink:

I wasn't thinking about aesthetics but rather about joint stability. You can "lock in" one dimension of the joint (i.e. if the boards that make the top are quarter sawn, then orient the grain in the leg similarly, and they will move together, keeping the joint tight). However the other dimension, the one that goes along the length of the table boards, will have something akin to a cross-grain situation. Even if wedged, the tenon will want to shrink and expand with the seasons, while the top will not in that direction. Over time the joint could work itself loose.

I might be over-cautious, and it's true that the humidity swings in the UK aren't as severe as in Canada, but still...

I know that Modernica uses that kind of joint for some of its tables, but as far as I can recall the whole table is made using man-made materials, where wood movement isn't an issue.

I guess that the solution is to try it and report back to us :wink:

DC

 

[woodbloke]

Hang on - isn't the wedge correct in the picture? The wedge has to press against end grain - turn it 90 degrees and it will split the top when you hammer the wedge in.
Clouding the waters.....
Philly

Phill - true... the wood will split ifyou use a thick enough wedge driven in parallel. All that's needed in this situation tho' is something to just splay the top of the leg so that a decent joint is obtained. A thicker wedge can be used for decorative effect if the saw cut it's going into is also wedge shaped, the wedge only needs to be tapped in maybe a few mm to grip - Rob

 

[David C]

The diagrams are correct though possibly a bit too close to the table top end for comfort.

It is most unwise to wedge in a direction that will split the table top if excessive force is applied to the wedge.

It is bad practice, i.e.wrong.

The only possible variation is a diagonal wedge.

Pairs of decorative wedges, as used frequently by Alan Peters are much more decorative. In fact he usually had two narrow tennons side by side, which is possibly the most elegant of all, as well as doubling the effective gluing area.

The wedge / wedges have nothing to do with compressing the best glue face, which should be a good fit just like any other tennon.

Decorative through wedged tennons call for precise work as they are viewed from the exit side.

Sorry to be dogmatic, but the reasons should be clear.

David C

 

[engineer one]

thanks david c. that was the answer i was hoping for.

my personal understanding was that the wedge was designed to stop the tenon from pulling down and out, but as you say demands great accuracy to ensure attractiveness.

since the leg is about 35 x35 mm i wonder how big(small) the tenon should be. i was thinking that 20-25x20-25 would be right, since in part all you are trying to ensure is that the leg will not be pulled or pushed through the top. then the wedges would be about 5mm thick max.

paul :wink:

 

[woodbloke]

I knew that somewhere in one of my texts I had seen pics of wedges with the grain as shown in this pic but cleary on closer inspection the grain will be in final outcome as LN originally indicated, so apologies for poor info, not something I normally try and give:

Note to self - fully engage grey matter before posting - Rob