Author Topic: How would you go about making these LAP JOINTS  (Read 3045 times)

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Offline Intex

  • Posts: 114
How would you go about making these LAP JOINTS
« on: September 04, 2019, 04:16 PM »
I would like to make this coffee table base of 3" thick oak, glued up to approx 12" wide. To make the "X" cross, I was thicking that the strongest goint would be a half-lap joint in the middle of the base pieces, wich would be approx a 6" deep by 3" wide cut in each cross member.

1) Would this be the best way to make the base
2) If so, what Festool tool could I use? The miter saw is too small to handle a 12" thick piece, and I wouldnt know how to use the track saw? Any ideas?
3) The only idea I have is to use 2 6" wide pieces for the glue up, and leave a 3" wide opening in the middle for the half-lap ??

Thanks!!

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Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #1 on: September 04, 2019, 04:17 PM »
Drawing of table included

Offline neilc

  • Posts: 2758
Re: How would you go about making these LAP JOINTS
« Reply #2 on: September 04, 2019, 05:40 PM »
Why not make the center a hollow column 3" x 3" - that would give you room inside to use lag screws or threaded inserts to attach the four sides of the legs.  Much easier to do with tools you probably have.  And it would not show to the exterior.

Getting an accurate cross cut on those pieces to make the 'x' at that size would be a challenge with a tight fit.  A large bandsaw could do it but you'd need an 18" or larger given the throat size you'd need.

Offline Birdhunter

  • Posts: 2724
  • Woodworker, Sportsman, Retired
Re: How would you go about making these LAP JOINTS
« Reply #3 on: September 04, 2019, 05:51 PM »
I built a similar table. After 4 or 5 design failures, I built a solid square core and used Dominos to attach the legs to the core. This worked and was easy to do.
Birdhunter

Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #4 on: September 04, 2019, 06:51 PM »
Birdhunter, that seems like the easiest solution. It then looks like I will be buying another one-off Festool Domino.
Did you have much trouble with glue ups , if using 3" stock?
I am also tooling around with the idea of having our lumber supplier do the glue up and cut the circle, but here in So Calif, this work is not cheap.

Offline Birdhunter

  • Posts: 2724
  • Woodworker, Sportsman, Retired
Re: How would you go about making these LAP JOINTS
« Reply #5 on: September 04, 2019, 07:52 PM »
My table had a rectangular top. No problem with the glue up.
Birdhunter

Offline Birdhunter

  • Posts: 2724
  • Woodworker, Sportsman, Retired
Re: How would you go about making these LAP JOINTS
« Reply #6 on: September 05, 2019, 05:33 AM »
I’ve done a circular table, but only 1.5” thick. I laid out the boards as they would be once joined together. I used a very sophisticated tool to draw the circumference (brad, string, and chalk). It is important to draw the circle BEFORE cutting the mortises. You do not want a mortise exposed when you cut the circumference. Made the cut with a jigsaw. Joined with Dominos. Sanded to perfect roundness.

I did run the boards through a jointer and planer as the first step. It’s also important to do the glue up in pieces and not try to glue up all the pieces at the same time.
Birdhunter

Online HarveyWildes

  • Posts: 871
Re: How would you go about making these LAP JOINTS
« Reply #7 on: September 05, 2019, 10:28 AM »

Picture a lap joint for this design if one of the pieces decides to cup slightly over time.  A simple lap joint makes it easy for the wood to move, and the glue joint between the side and end grain in the lap would be a potential point of failure.  For the length and width of your pieces, I would not use a lap joint without modification.  Here are some of suggestions for increasing the strength of the lap joint, if you decide that's still what you want.

(1) Put shoulders on the lap joints to make sure that all of the cut edges of the lap were captured tightly in the mating piece.
(2) Dovetail the shoulders to reduce the ways the wood can move even more.
(3) Cut 3" laps rather than 6" laps.  One board would be 12" wide with 3" laps on each side.  The other would be in two pieces for cutting the laps, each with a 3" lap.  Once the laps are cut, sandwich the first board between the second two boards.  (Use dominos to make sure the second two pieces are are lined up as precisely as possible when you glue them around the first piece, then scrape the joint smooth when dry.)  Again, using shoulders to define the laps would increase the strength, as would dovetailing the shoulders.


Alas, no one would appreciate the design complexity of the joint you had cut without turning the table upside-down.


All of those suggestions are going to make the project stronger, but that comes at a cost.  They all make the project more labor intensive, more complex, and more risky.  If you have to make money on the project, or you have a short time to do it, then maybe you want to stick with the quicker options.  But if you are doing it for the joy of it, and/or it's within your skill level, time budget, and risk tolerances, the extra work will result in a stronger table.


If you go the domino route (which I also like better than simple lap joints), I would still use shoulders on the joints to help with keeping the joints at 90 degrees and to make life easier for the dominos over time.


Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #8 on: September 05, 2019, 07:45 PM »
HarveyWildes,
No these are not for a paying client- my daughter, so I want to do it the best way I can, without risking ruining it, as the wood is pretty expensive here in So. Cal.
I think I will try the Domino method, but I am not sure what you mean by "Shoulders" on the pieces, if I would be dominoing on four sides of a 3" x 3" center post, I guess you would cut a shoulder into the top of one of the 3" x 15" legs and then a rabbet into the column to accept the shoulder ???

Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #9 on: September 05, 2019, 08:04 PM »
It looks like Im going to have to buy a Festool Domino cutter (My Porter Cable Biscuit cutter is useless) I hope that the model 500 will work out for pieces this large, because I dont want to get the model 700- just too big, Ill probably never use it again.

Offline Jiggy Joiner

  • Posts: 804
Re: How would you go about making these LAP JOINTS
« Reply #10 on: September 06, 2019, 04:08 AM »
There’s a few ways this could be done.
Instead of four equal pieces for the legs, have a double length piece that will be two legs, cut female dovetails to either side of centre, then cut male dovetails to the ends of the two legs. With the top secured, this will be a durable method.

Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #11 on: September 06, 2019, 07:42 PM »
Jiggy, OK, since I havent cut dovetails without a router jig, what would the best/easiest way to make a dovetail joint to attach the north & South legs to the one piece East-West leg?

Offline neilc

  • Posts: 2758
Re: How would you go about making these LAP JOINTS
« Reply #12 on: September 06, 2019, 11:26 PM »
i'd mark out the shoulders for the narrow part of the dovetail.  Use your router with a plunge bit and guide to route out the bulk of the material. (essentially a mortise).  Then use chisels to do the undercut to form the dovetail.

A little time with a couple of handplanes and a backsaw would let you cut the matching pin on the two legs.


Offline Birdhunter

  • Posts: 2724
  • Woodworker, Sportsman, Retired
Re: How would you go about making these LAP JOINTS
« Reply #13 on: September 07, 2019, 05:01 AM »
I simply do not understand the need for anything except a truly square central body and square ends on the legs that get Dominoed to the square central body.  A jointer and a planer will produce a square central body. There are many ways to square up the leg ends.
Birdhunter

Offline Jiggy Joiner

  • Posts: 804
Re: How would you go about making these LAP JOINTS
« Reply #14 on: September 07, 2019, 07:31 AM »
@Intex Sorry, I should have been more specific. I mean join them with sliding dovetails, like for joining drawer shelves etc.
Just full dovetail channels/tails almost full height of the main piece, then full length pins cut to to smaller pieces.

I'll try and find some pics

Edit: Like this, just imagine these are your table legs.



« Last Edit: September 07, 2019, 07:39 AM by Jiggy Joiner »

Offline tomp

  • Posts: 97
Re: How would you go about making these LAP JOINTS
« Reply #15 on: September 07, 2019, 07:57 AM »
I don't know how long the legs are going to be - maybe estimate around 30" from the sketch - but they're going to be pretty heavy in solid wood. How about making two hollow boxes, 12" high by the length needed, with mitered corners so that no end grain shows. Make a jig to cut parallel notches in both sides of both boxes for the half laps using a router, square up the bottom of the notches with a chisel and  slide the two sections together. The hollow legs will allow you to hide the attachment to the underside of the top.

Offline derekcohen

  • Posts: 338
    • In The Woodshop
Re: How would you go about making these LAP JOINTS
« Reply #16 on: September 07, 2019, 12:47 PM »
I would like to make this coffee table base of 3" thick oak, glued up to approx 12" wide. To make the "X" cross, I was thicking that the strongest goint would be a half-lap joint in the middle of the base pieces, wich would be approx a 6" deep by 3" wide cut in each cross member.

1) Would this be the best way to make the base
2) If so, what Festool tool could I use? The miter saw is too small to handle a 12" thick piece, and I wouldnt know how to use the track saw? Any ideas?
3) The only idea I have is to use 2 6" wide pieces for the glue up, and leave a 3" wide opening in the middle for the half-lap ??

Thanks!!

You can use a Festool dovetail saw and Festool chisels :)

This is the joint you want ...



A little more complicated as the cross is more oblique and, therefore, the saw cuts are angled and not square.



As you can see, it is a lap joint ..



More details here: http://www.inthewoodshop.com/Furniture/CoffeeTableForJamie.html

Regards from Perth

Derek
« Last Edit: September 07, 2019, 12:50 PM by derekcohen »

Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #17 on: September 07, 2019, 07:15 PM »
Jiggyjoiner
I think I will take your advice with a slight change. Since the legs are mounted 90 degrees to each other, I will do away with the center post, and make one leg the length of two reg legs, then put dovetails into each side of the center of the long leg for the two 90 degree legs

I’m hoping I can find a large dovetail bit for my router

Offline deepcreek

  • Posts: 849
    • TimberFire Studio
Re: How would you go about making these LAP JOINTS
« Reply #18 on: September 07, 2019, 10:55 PM »
@Intex

Have you considered the final weight of this table?

I'm concerned it may be far heavier than you realize.

I apologize if that is your intent.

Just trying to be helpful.

Joe
Joe Adams
TimberFire Studio
Houston, Texas

http://www.facebook.com/timberfire

Offline Svar

  • Posts: 1871
Re: How would you go about making these LAP JOINTS
« Reply #19 on: September 07, 2019, 11:02 PM »
There’s a few ways this could be done.
Instead of four equal pieces for the legs, have a double length piece that will be two legs, cut female dovetails to either side of centre, then cut male dovetails to the ends of the two legs. With the top secured, this will be a durable method.
That's what I would do. To simplify you could substitute dovetails with floating tenons.
I would not do half lap joint this size.

Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #20 on: September 08, 2019, 12:27 AM »
Deepcreek
Yes, I know its probably going to be 250-300 lbs, At least not a throw away piece of furniture

Offline Jiggy Joiner

  • Posts: 804
Re: How would you go about making these LAP JOINTS
« Reply #21 on: September 08, 2019, 04:18 AM »
@Intex That’s exactly how i meant, the post in the photos was just to shown a sliding dovetail, the second photo is a better example, showing one side of the joint. You would use a double length board for two legs, cut the tails/channels/female dovetail into both sides of that board leaving a stop.

Then cut the pins/male dovetails to the smaller leg, also leaving the same stop.

There are other ways this joint could be done, quite a few in fact but, this is a fairly straight forward way, and durable once the top is fixed.

Offline derekcohen

  • Posts: 338
    • In The Woodshop
Re: How would you go about making these LAP JOINTS
« Reply #22 on: September 08, 2019, 11:47 AM »
Jiggyjoiner
I think I will take your advice with a slight change. Since the legs are mounted 90 degrees to each other, I will do away with the center post, and make one leg the length of two reg legs, then put dovetails into each side of the center of the long leg for the two 90 degree legs

I’m hoping I can find a large dovetail bit for my router

You are making this awfully complicated for simple joinery. All that is required is a lap joint as i have shown. No dovetails or mortice and tenon joinery needed. This is especially easy if the parts are square to one another. You could do this joint on a tablesaw or use a handsaw, and complete it in under 15 minutes.

Here's a video:



Regards from Perth

Derek

Offline ChuckM

  • Posts: 1292
Re: How would you go about making these LAP JOINTS
« Reply #23 on: September 08, 2019, 12:14 PM »
I, too, will go with the lap joint for this kind of cross-base build: http://tinyurl.com/y6l6xojp

I use dominoes a lot, but won't use them on this one just because I can. The sliding dovetail joint isn't as straight forward as it looks to cut, unless you have the right set-up, or have enough spare stock to do the necessary test cuts. Compared to the lap joint, there is extra work without any extra benefits.
« Last Edit: September 08, 2019, 12:29 PM by ChuckM »

Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #24 on: September 08, 2019, 04:01 PM »
Derek,
Thank you for the advice. My only concern is that since the base legs are 12" high, the cut would be 6" deep. Too deep for my Kapex with the stop feature, and too deep for the tracksaw or router. I am still waiting for the Festool sawstop to come out, but probably too deep for that as well.

Alternative is to take it to a shop that has a larger table saw with dados.

Offline ChuckM

  • Posts: 1292
Re: How would you go about making these LAP JOINTS
« Reply #25 on: September 08, 2019, 04:54 PM »
The Kapex can handle the job well, if you have a flush trim router bit.

First, cut out the notch as deep the Kapex can cut. Then rout out the remaining part with a straight bearing trim bit. In the last step, clean up the corner with a sharp chisel.

Alternatively, use scribed lines to define the waste, jigsaw or drill most of the waste away, and clean up the rest with a chisel.

Either way, try it out on some 2x6 scrap to refine your technique.
« Last Edit: September 08, 2019, 05:04 PM by ChuckM »

Offline derekcohen

  • Posts: 338
    • In The Woodshop
Re: How would you go about making these LAP JOINTS
« Reply #26 on: September 08, 2019, 07:51 PM »
Derek,
Thank you for the advice. My only concern is that since the base legs are 12" high, the cut would be 6" deep. Too deep for my Kapex with the stop feature, and too deep for the tracksaw or router. I am still waiting for the Festool sawstop to come out, but probably too deep for that as well.

Alternative is to take it to a shop that has a larger table saw with dados.

One alternative is to saw as deeply as your Kapex will permit, then use the kerf to guide a hand saw to complete the remainder.

Another is to mark it all out, knife in a chisel line all around, and let the hand saw track in that.

Bandsaw?

Regards from Perth

Derek

Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #27 on: October 03, 2019, 08:26 PM »
I have begun the build, starting with the base. I decided to do a CROSS LAP JOINT, but i will make the cut with wood, instead oif cutting it in:

Since the legs are 2 cross pieces, 12" high by 3" thick, I will make each one of the two cross members from 6" wide pieces glued up, since it is very hard to get 12" wide 12/4 white oak here. INSTEAD of gluing the two pieces together, I will glue two pieces on top of one longer piece, while keeping a 3" void in the middle. Since I am going to have to glue up these pieces anyway, why not leave the 3" gap while gluing the two 6" wide legs together to get a 12" wide leg. I will probably make the channel a bit narrower (ie:L 2/15/16") and chisel it to a tight fit.

I will use Dominoes to help with the glue up.

Which orientation is best for the glue up of the pieces, reverse grain direction in left drawing or same grain direction in right drawing.

Thanks everyone.

PS- I did have to go and buy a Festool domino for the base and top

Offline ChuckM

  • Posts: 1292
Re: How would you go about making these LAP JOINTS
« Reply #28 on: October 03, 2019, 08:49 PM »
From the joint strength point of view, since it is long-grain to long-grain, dominoes won't be necessary. They will help with the alignment keeping the pieces from sliding, but I'm sure you'll find plenty of uses for the DF.

Grain orientation: the mating pieces should both have their heart sides facing out.

heart side
[__________]
Glue
___________
[                  ]
heart side
« Last Edit: October 03, 2019, 09:25 PM by ChuckM »

Offline Intex

  • Posts: 114
Re: How would you go about making these LAP JOINTS
« Reply #29 on: October 04, 2019, 11:55 AM »
Chuck,
Since they are being glued SIDE FACE to SIDE FACE, Im not sure I understand. My only alternative is as in the drawing I attached, the left drawing or right drawing ?