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Forum topic by tommyc325 posted 09-13-2016 07:14 PM 521 views 0 times favorited 16 replies Add to Favorites Watch
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tommyc325

54 posts in 819 days


09-13-2016 07:14 PM

Hi Everyone

I’m working on a vanity project where I have two aprons joining into a leg. Both aprons and the leg are 1.5-inch square walnut.

I designed how I would join this in sketchup and attached a screen shot below.
Should this hold together well? I guess I’m worried about the 3/8” excess.

This will be my first time doing mortise and tenon so I am absolutely a newbie.

https://cl.ly/hS5A


16 replies so far

View Aj2's profile

Aj2

689 posts in 1261 days


#1 posted 09-13-2016 07:46 PM

I think it will be ok.The fit of your jointery will play its part in the strength.
The other options are a double tenon more glue surface.
If it’s the top of a leg you can also cut your mortise and tenon all the way to the top of the leg.
And get more glue surface.

Aj

View JBrow's profile

JBrow

818 posts in 383 days


#2 posted 09-14-2016 12:58 AM

tommyc325,

I am not sure what you mean by 3/8”excess. If it is the 3/8” x 3/8” section of the leg at the inside corner of the leg left after chopping the mortises, I agree that it may weaken the joint by weakening the leg at the joint. Reducing the width of the tenon by to ½” would leave the joint plenty strong while adding some material to the inside corner of the two mortises, leaving the leg a little stronger at the joint. Even though glue in the snug fitting ¾” wide mortises and tenons would strengthen the joint and as well as the 3/8” x 3/8” inside corner of the mortises, I would reduce the mortise and tenon width to ½”.

View pintodeluxe's profile

pintodeluxe

4854 posts in 2276 days


#3 posted 09-14-2016 01:38 AM

Need more information about what the project is, and what the intended use is. A coffee table for instance would benefit from taller aprons.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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tommyc325

54 posts in 819 days


#4 posted 09-14-2016 01:50 AM


tommyc325,

I am not sure what you mean by 3/8”excess. If it is the 3/8” x 3/8” section of the leg at the inside corner of the leg left after chopping the mortises, I agree that it may weaken the joint by weakening the leg at the joint. Reducing the width of the tenon by to ½” would leave the joint plenty strong while adding some material to the inside corner of the two mortises, leaving the leg a little stronger at the joint. Even though glue in the snug fitting ¾” wide mortises and tenons would strengthen the joint and as well as the 3/8” x 3/8” inside corner of the mortises, I would reduce the mortise and tenon width to ½”.

- JBrow

Thank you – YES this is exactly what i was talking about. Here’s a screenshot with the new dimensions. Please let me know if this is what you were talking about.

This edit makes the “excess” 1/2”

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JBrow

818 posts in 383 days


#5 posted 09-14-2016 02:20 AM

tommyc325,

The dimensions were a little difficult to read, but if my old eyes worked well enough, it looks like the revised design calls for a centered tenon (and mortise) with ½” shoulders. That should strengthen the joint and I see no reason why this joint would not work for the vanity. Whenever possible I like to ensure there is no mortise wall whose thickness is less than the thickness of the tenon. Your revised design meets my personal criteria.

With a little care and several trial and error mitre cuts on the ends of the tenons would preserve the maximum area of the cheeks while allowing the joints to fully seat. The mechanical strength of the mortise and tenon joint is enhanced mostly as a result of the glue bond of the tenon cheeks to the mortise walls.

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tommyc325

54 posts in 819 days


#6 posted 09-14-2016 02:33 AM



tommyc325,

The dimensions were a little difficult to read, but if my old eyes worked well enough, it looks like the revised design calls for a centered tenon (and mortise) with ½” shoulders. That should strengthen the joint and I see no reason why this joint would not work for the vanity. Whenever possible I like to ensure there is no mortise wall whose thickness is less than the thickness of the tenon. Your revised design meets my personal criteria.

With a little care and several trial and error mitre cuts on the ends of the tenons would preserve the maximum area of the cheeks while allowing the joints to fully seat. The mechanical strength of the mortise and tenon joint is enhanced mostly as a result of the glue bond of the tenon cheeks to the mortise walls.

- JBrow

The left and right shoulders are 1/2” the top & bottom shoulders are 3/8”

The tenon is 3/4” Tall by 1/2” Wide and 1” Long

are you suggesting that i make the tenon 1/2” square and 1” Long?

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Aj2

689 posts in 1261 days


#7 posted 09-14-2016 02:52 AM

Usually you can just split up everything into 1/3s.Make them as long as possible leave some space between the miters ends for glue.
You don’t need a shoulder above the tenon if its the top of the leg.So make he tenon taller to the top of the leg.It will also be easy to pare in the mortise if you need to.
There not a lot to wrk with so there is really much of a choice.
Right?

Aj

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tommyc325

54 posts in 819 days


#8 posted 09-14-2016 03:19 AM


Usually you can just split up everything into 1/3s.Make them as long as possible leave some space between the miters ends for glue.
You don t need a shoulder above the tenon if its the top of the leg.So make he tenon taller to the top of the leg.It will also be easy to pare in the mortise if you need to.
There not a lot to wrk with so there is really much of a choice.
Right?

Aj

- Aj2

Thanks AJ – I attached the actual project that I’m working on. 3 Sets of aprons.

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JBrow

818 posts in 383 days


#9 posted 09-14-2016 12:32 PM

tommyc325,

No, I was not suggesting a square tenon. I was speaking of the shoulders on the sides of the tenon as being ½”. The 3/8” top and bottom shoulders are fine; probably resulting in a little stronger joint than with a square tenon since there is more glue surface on the cheeks with 3/8” top and bottom shoulders.

Depending on how you cut the tenon, cutting a square tenon at the table saw with a dado blade can be a little faster since there is only one set up. I have found when mortising at the top or bottom of a leg, the smaller piece of wood that bridges the mortise at the end of the leg can sometime crack if not careful. The mortise like that suggested by Aj2 (open at the end of the leg) not only increases glue surface but also eliminates the occasional cracking problem.

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Aj2

689 posts in 1261 days


#10 posted 09-14-2016 01:46 PM

I like your taste.I one last year for for our house in hickory.
I left off the long aprons.

Fun project good luck.

Aj

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rwe2156

2192 posts in 944 days


#11 posted 09-14-2016 02:16 PM

I would go with 1/4” shoulders on the outside and 1” on the inside.

But what you’ve designed will work.

-- Everything is a prototype thats why its one of a kind!!

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tommyc325

54 posts in 819 days


#12 posted 09-14-2016 10:37 PM



tommyc325,

No, I was not suggesting a square tenon. I was speaking of the shoulders on the sides of the tenon as being ½”. The 3/8” top and bottom shoulders are fine; probably resulting in a little stronger joint than with a square tenon since there is more glue surface on the cheeks with 3/8” top and bottom shoulders.

Depending on how you cut the tenon, cutting a square tenon at the table saw with a dado blade can be a little faster since there is only one set up. I have found when mortising at the top or bottom of a leg, the smaller piece of wood that bridges the mortise at the end of the leg can sometime crack if not careful. The mortise like that suggested by Aj2 (open at the end of the leg) not only increases glue surface but also eliminates the occasional cracking problem.

- JBrow

Hey JBrow

So had a small change in the design process. I will be using 1.75 square stock for my legs and rails.
Any suggestions on how my tenon should be in this situation? I took a guess and have the design below.

::Note:: Im not married to using mortise and tenons but Im not sure what will work best for this situation.

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JBrow

818 posts in 383 days


#13 posted 09-15-2016 01:53 AM

tommyc325,

The mortise and tenon joint redrawn with 1.75” stock should work well. Your most recent diagram does not show shoulders on the tenons at the top and bottom of the tenons. For the bottom and center frames, these top and bottom shoulders will allow the mortises in the legs to be fully concealed by the frame. A bottom shoulder on the top frame tenons would allow the bottom of the upper-most mortises to be concealed. The vanity top will conceal the top of the upper-most mortises should you elect to make the upper-most mortises open at the top.

I think the ¾” long tenons are long enough to create a strong joint and make the mitred ends of the tenons unnecessary. Nothing wrong with the mitred tenons and I would probably mitre the ends of the tenons. The longer mitred tenons would add strength to the joint and the ends of the tenons would be easily mitred. It is just that by increasing the size of the workpieces generated an option on how to do the tenons. Additionally if you happen to cut the mitred end of a tenon in the wrong direction, a mistake I make all too often, the tenon can be simply cut to the ¾” length.

I can think of several alternative joints for joining the frame to the legs. But a well-executed mortise and tenon joint is a strong and classic joint and is a joint I use often. There are some tips for creating this joint and overall it is fairly straightforward joint making it doable for your project. Chief among the tips is to cut some tenons in a test piece before cutting the tenons in the work pieces. My general preference is to cut the mortises first because I find it little easier to fine tune a slightly oversized tenon for a perfect fit than it is to pair the walls of a mortise with a chisel. Also ensuring the mortises are all consistently cut so the mortises are the same width and the distance of the mortises from your reference face of the legs is consistent makes cutting all the tenons easier. Better yet is to ensure the mortises are centered on the work piece, which could be achieved with a router, maybe a jig, and a straight bit.

A simple alternative joint that comes to mind is a lap joint. If the joint is well fitted, it can be attractive. Biscuited or doweled joints are also simple and could be used, but in my opinion these are weaker than the mortise and tenon or lap joint. Joinery I do not use is pocket screw joinery but it is also an option. My disdain for pocket screw joinery is the cone shaped pockets left behind after the joint is assembled.

View tommyc325's profile

tommyc325

54 posts in 819 days


#14 posted 09-15-2016 02:57 AM


tommyc325,

The mortise and tenon joint redrawn with 1.75” stock should work well. Your most recent diagram does not show shoulders on the tenons at the top and bottom of the tenons. For the bottom and center frames, these top and bottom shoulders will allow the mortises in the legs to be fully concealed by the frame. A bottom shoulder on the top frame tenons would allow the bottom of the upper-most mortises to be concealed. The vanity top will conceal the top of the upper-most mortises should you elect to make the upper-most mortises open at the top.

I think the ¾” long tenons are long enough to create a strong joint and make the mitred ends of the tenons unnecessary. Nothing wrong with the mitred tenons and I would probably mitre the ends of the tenons. The longer mitred tenons would add strength to the joint and the ends of the tenons would be easily mitred. It is just that by increasing the size of the workpieces generated an option on how to do the tenons. Additionally if you happen to cut the mitred end of a tenon in the wrong direction, a mistake I make all too often, the tenon can be simply cut to the ¾” length.

I can think of several alternative joints for joining the frame to the legs. But a well-executed mortise and tenon joint is a strong and classic joint and is a joint I use often. There are some tips for creating this joint and overall it is fairly straightforward joint making it doable for your project. Chief among the tips is to cut some tenons in a test piece before cutting the tenons in the work pieces. My general preference is to cut the mortises first because I find it little easier to fine tune a slightly oversized tenon for a perfect fit than it is to pair the walls of a mortise with a chisel. Also ensuring the mortises are all consistently cut so the mortises are the same width and the distance of the mortises from your reference face of the legs is consistent makes cutting all the tenons easier. Better yet is to ensure the mortises are centered on the work piece, which could be achieved with a router, maybe a jig, and a straight bit.

A simple alternative joint that comes to mind is a lap joint. If the joint is well fitted, it can be attractive. Biscuited or doweled joints are also simple and could be used, but in my opinion these are weaker than the mortise and tenon or lap joint. Joinery I do not use is pocket screw joinery but it is also an option. My disdain for pocket screw joinery is the cone shaped pockets left behind after the joint is assembled.

- JBrow

JBrow

First off I would like to say thank you for all your help to this point so far. If you think there are other joints that can get this project done I think I would rather go that route since Ive never done mortise and tenon before and this project calls for ALLOT.

I would like to do lap joints but im not sure if my design here is the way to do it.

https://s3.amazonaws.com/vs-lumberjocks.com/odh58jt.jpg

How would this work?

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JBrow

818 posts in 383 days


#15 posted 09-15-2016 02:45 PM

tommyc325,

For some reason my security software blocked the link you posted as malicious so I could not take a look.

The sketch I have posted is one way to execute the lap joint. I have drawn it with the ends of the front and side rails mitred and so the rails and the leg faces set flush. The sketch shows the top rail/leg lap joint, where the top of the leg is rabbeted. Dados would be cut in the legs for the mid and bottom rails. This design is the most difficult method for executing the joint. Cutting the mitres to fit well and ensuring the faces of the rails and the leg faces are flush requires a lot of setup adjustments and test cuts.

My method for executing the joint would be to cut away material from the legs first, taking great care to ensure the opposite edges of the rails fit perfectly within the leg dados. If you want the rails and legs to set flush on the outside face, making test cuts on a piece of scrape rail and then clamping the test piece to the leg would probably be the most sure way to dial in that flush fit. Sometimes if the test piece is set into the leg dados without clamping the clamping pressure applied during glue-up can pull the rail into the joint a tiny bit spoiling what was thought to be a flush fit.

Once the rails set flush to the face of the legs, accurately marking and then making the first mitre cuts a little long would allow for subsequent skim cuts until the mitre joint line is perfected.

Since cutting tight fitting mitres on the ends of the rails could be difficult and time consuming, a design change could eliminate the mitred ends of the rails. The alternative is to cut the rabbet on the front rail long enough to overlap and cover the end grain of the rabbet on the side rails. The rabbet on the side rails would be cut shorter. This would eliminate the appearance of end grain while viewing the vanity from the front; end grain from the joint would be visible when the vanity is viewed from the sides.

I find that numerous test cuts are required to end up with flush lap joints. A design change could reduce the set up time needed to find the proper depth of the rabbets in the rails. The rails could set proud of the face of legs by 1/8” or ¼”. The rabbets in the legs would be cut no deeper than required to achieve the offset of the rails. I would make this adjustment by reducing the depth of the dados in the legs and leave ¾” on the rails. For a ¼” offset of the rail from the face of the leg, the rabbets in the rails would remain at ¾” (i.e. 1” of material removed). The depth of the dados in the legs would be reduced from ¾” to ½”, leaving some additional material on the legs.

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