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Forum topic by Spikes posted 10-16-2018 04:22 PM 1840 views 0 times favorited 16 replies Add to Favorites Watch
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Spikes

71 posts in 217 days


10-16-2018 04:22 PM

Dear all,

I’m in my six month learning woodworking and one recurring problem I’m having is lack of trust of what I build, specifically that it will hold fine over time as it gets used. The most simple example I can give is a meditation bench I’m working on, here’s a pic for reference:

These are two of the main questions I have no good answer for and I’d love some pointers on how to acquire this kind of knowledge:

  • first off, the material. In my case I’m working with redwood, and this board seems very dry. The benches I’ve seen were made of oak. This redwood is very soft and feels brittle. In some bench designs the legs are made to detach and attach with a dovetail joint. I’ve tried to do that and the result is that I can break the joint part by hand on a 3/4 wide leg. I could not do anything like that to the oak bench a friend showed me.
  • the type of joint/design. Say I’m just doing a butt joint glueing the legs to the top. Since the legs are not connected to each other likely a sideways force of someone sliding over would likely snap them. But what if I carved a recess to slot the leg in 1/2 inch? or what if I drilled holes through the top and into the leg and added dowels? would that make it strong enough? what if I used screws instead of dowels? what size of screw or dowel? And obviously there are variables around the length… even strong enough joints would run into trouble if the top was very long with legs at the end… I’m sure somehow there are approaches to know how long you can go.

In this case I could easily test it, altho I wasted that piece of wood, but isn’t there a way to know this kind of stuff before hand (without going to get a PHD in physics or something)? And this is especially concerning over time as something may be solid at the time of construction but give over a few months or a year.

I’d love o learn how to design and make stuff that lasts and, more importantly, is safe for others, but all the courses and videos I’ve watched never seem to tackle this kind of questions and just give you plans that you’re supposed to trust.

thanks in advance,

Spike

-- Don't worry about making progress, worry about practicing. If you practice you will make progress even if you don't want to.


16 replies so far

View LittleShaver's profile

LittleShaver

411 posts in 791 days


#1 posted 10-16-2018 05:13 PM

I’ve been coached by my wife, who’s motto is “If you’re going to build it, over build it.”

For your project, I would add a board with a graceful arch stretching between the verticals at the top of the verticals.
I really don’t care for screws, so I would peg the top the the verticals and the stretcher to the top and verticals using a contrasting wood.

YRMV.

-- Sawdust Maker

View jamsomito's profile

jamsomito

254 posts in 597 days


#2 posted 10-16-2018 05:24 PM

For joinery, the sky is the limit. You have tons of options. What I usually do is make the general design, then figure the joinery to give strength where needed and aesthetics where needed. If they’re not lining up, reconsider the design like LittleShaver mentioned.

In the picture you posted, the bench will be weak in the side-to-side racking direction. So, you want to make a joint to accomodate that. Butt joint with glue will be end-grain to long grain… not very strong because the end grain will soak up the glue and it won’t adhere as well. A dado like you described would definitely help some – if it’s oak, 1/2” would probably be ok if you have tools/skill enough to do it without slop (I would question my own ability to do that), but still won’t offer the best support. A through-tenon with a shoulder to take the vertical weight would offer you the most support in your case. Dowels can mimic this to an extent and would likely be a good option if you put enough of them in (maybe 4-5 along the length of the leg). Screws wouldn’t be great because as you screw down through the top into the legs, you are putting the threads into the end grain which is a weak joint. In this particular case, dowels will work much better than screws because they will have long-grain contact in at least some sides of the piece in both the legs and the top for the glue to take hold onto.

All that said, I would definitely try to add a “stretcher” of sorts between the legs to give it the lateral support it needs. Then the top just needs to be kept in place instead of providing lateral support at the joints.

View EarlS's profile

EarlS

1756 posts in 2519 days


#3 posted 10-16-2018 05:43 PM

A good way to learn is to look at finished projects similar to what you want to build and see what everything looks like. You might not like the style, but focus on the construction. Look at the individual pieces of wood that make up the overall piece. Generally, you can’t go wrong if you make sure your piece has all of the same components. Most pieces have the same basic components, the only difference is the style used to make the components.

From there you can start to learn about the various methods of connecting the pieces together and what makes a better joint.

Hopefully, all of this makes some sense. Read some of the build blogs on LJ and you will get a sense of how folks go about building high quality projects that are durable, long lasting, and beautiful. Most of all, it takes practice.

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

View bondogaposis's profile

bondogaposis

5048 posts in 2522 days


#4 posted 10-16-2018 07:25 PM

For that bench to be long lasting, I would make dadoes in the underside of the top for the legs, 1/4” deep is plenty. Then use screws, plugs and glue to attach the legs. Then make a stretcher to go between the legs and attach it using mortise an tenon joint.

-- Bondo Gaposis

View Spikes's profile

Spikes

71 posts in 217 days


#5 posted 10-16-2018 10:09 PM

thank you for all the comments, agree on the dado and the arch, however being a meditation bench the arch would impede leg movement so it’s not an option.

@jamsomito , a couple things in your comment that I’d like to explore.

First off, I’m reading up on end-grain to face grain glue up and why that’s a problem, it seems that thinning he glue and having it soak in in a firs pass may fix that. However I don’t understand why end grain is an issue with the screw, could you elaborate? I’ve ordered “Understanding Wood”, I’m hoping it will address some of his basic knowledge I seem to lack.

Second you mentioned dowels being a stronger option than screws. I don’t understand this, one is metal, one is wood… how is a 5/8 piece of maple going to take more side-to-side racking force than a piece of metal? I understand that the glue on both ends of the dowel would form a stronger bond than the screw in the end grain, but I still fear that the side racking would just snap the dowels compared to 2 long screws. And I can’t put 4-5 in, at most 2. Also according to the interwebs, a dowel joint isn’t necessarily stronger than a screw joint, altho the screw ones seem to deflect sooner.

thanks for your insight and pardon the ignorance, trying my best to fill the gap.

Spike

-- Don't worry about making progress, worry about practicing. If you practice you will make progress even if you don't want to.

View lumbering_on's profile

lumbering_on

559 posts in 661 days


#6 posted 10-16-2018 10:36 PM


thank you for all the comments, agree on the dado and the arch, however being a meditation bench the arch would impede leg movement so it s not an option.

@jamsomito , a couple things in your comment that I d like to explore.

First off, I m reading up on end-grain to face grain glue up and why that s a problem, it seems that thinning he glue and having it soak in in a firs pass may fix that. However I don t understand why end grain is an issue with the screw, could you elaborate? I ve ordered “Understanding Wood”, I m hoping it will address some of his basic knowledge I seem to lack.

Second you mentioned dowels being a stronger option than screws. I don t understand this, one is metal, one is wood… how is a 5/8 piece of maple going to take more side-to-side racking force than a piece of metal? I understand that the glue on both ends of the dowel would form a stronger bond than the screw in the end grain, but I still fear that the side racking would just snap the dowels compared to 2 long screws. And I can t put 4-5 in, at most 2. Also according to the interwebs, a dowel joint isn t necessarily stronger than a screw joint, altho the screw ones seem to deflect sooner.

thanks for your insight and pardon the ignorance, trying my best to fill the gap.

Spike

- Spikes

I’m not sure where you heard that you could get a good butt joint from applying thinned glue; however,there’s a reason that we have joints such as mortise and tenons, dovetail, and finger. The reality is that it’s not the strength of the glue because you can actually get wood failure with a butt joint. The fact is that the fibers at the end joints are just too weak to produce a strong joint.

Dowels are also much stronger than screws, at least if done correctly. Screws may be harder and stiffer, but that has little do do with how well the joint will hold. Screws will bend and tear the joint, but hardwood dowels will flex and provide more support.

View Tony_S's profile

Tony_S

939 posts in 3254 days


#7 posted 10-16-2018 11:04 PM

Two wedged through tenons on each leg. No skirt or stretcher needed….strong like bull….forever.

https://www.google.com/search?client=firefox-b&biw=1088&bih=501&tbm=isch&sa=1&ei=TWvGW6q_MsOQ0wLUnaP4CA&q=wedged+through+tenon&oq=wedged+through&gs_l=img.1.1.0l3.581078.587624..593443...0.0..3.149.3146.3j23......2....1..gws-wiz-img.....0..0i24j35i39j0i67j0i10j0i8i30j0i10i24.oOcQABkBKNs

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

View jamsomito's profile

jamsomito

254 posts in 597 days


#8 posted 10-17-2018 01:27 AM


First off, I m reading up on end-grain to face grain glue up and why that s a problem, it seems that thinning he glue and having it soak in in a firs pass may fix that. However I don t understand why end grain is an issue with the screw, could you elaborate? I ve ordered “Understanding Wood”, I m hoping it will address some of his basic knowledge I seem to lack.

I have heard of this approach before, but I’m still skeptical. If you think of a tree, it has to get water and nutrients from the roots to the leaves, and it gets “sucked” up through the trunk to the top. The grain structure is running vertically. Imagine grabbing a handful of plastic soda straws – drip some water on the sides of the bundle and it doesn’t do much, maybe goes in a layer or so. Drip it on the ends and it goes all the way through. Wood grain is the same way – porous on the ends, and nice “grippy” long crevasses to grab onto on the edges. Glue likes the edge grain. The end grain will just suck it all through and not leave any in the joint. By thinning it and saturating the end grain you essentially plug up those pores, then allow the 2nd layer of glue to bond to whatever rough surface is left. The problem is, wood glue isn’t designed to work this way. Other adhesives would work better in this case. In a pinch, wood glue can work alright like this, but there are many, stronger alternatives.


Second you mentioned dowels being a stronger option than screws. I don t understand this, one is metal, one is wood… how is a 5/8 piece of maple going to take more side-to-side racking force than a piece of metal? I understand that the glue on both ends of the dowel would form a stronger bond than the screw in the end grain, but I still fear that the side racking would just snap the dowels compared to 2 long screws. And I can t put 4-5 in, at most 2. Also according to the interwebs, a dowel joint isn t necessarily stronger than a screw joint, altho the screw ones seem to deflect sooner.

This doesn’t have to do with metal vs wood. Actually, in the case of a cheap drywall screw, the wood would be stronger. But I digress. The issue here is the directional strength of wood. Go back to the straw analogy. Cut your bundle of straws across the length, and it would take some effort (cross cut):

Cut it down the length and the knife will find its way in between the straws (fibers of wood) and cut a bit more easily (rip cut). Cut it down the ends and the bundle will split down the grain lines (split):

It’s the same thing with the wood. Screw in sideways and you’re pulling those straws against the strength of all the other fibers above it. Screw into the end grain and you’re just stacking end-grains between your threads and they will break off on the grain lines and shear right out with minimal effort. I found this picture online:

With a dowel hole down into the end grain, you are exposing long grain all around the circumference of that hole, which in turn will mate with long grain all down the length of the dowel, and essentially make an extension of the piece of wood (glue dries stronger than the wood itself). This is the strongest way to fix a dowel in place. Now, the hole in the cross-grain top will have both long grain and end grain exposed, but the half of the hole wall area with edge grain exposed will be plenty strong enough to keep the dowel in place. Any shear forces will be absorbed by the dowel itself, which if you get hardwood dowels (common), will be just as strong as a mortise and tenon joint (assuming you have multiple, dowel-sized mortise and tenons). The advantage of a mortise and tenon is they are bigger than dowels and are true extensions of the wood instead of a “floating” tenon (aka dowel) that’s glued on each side.


thanks for your insight and pardon the ignorance, trying my best to fill the gap.

Spike

- Spikes

No worries! I was there and I’m still learning every day. Hope this helps somewhat.

View Lazyman's profile

Lazyman

2559 posts in 1559 days


#9 posted 10-17-2018 01:49 AM

A butt joint will not work. If I was making this, I would use a box joint with 2 stretchers between them against underside of the top to strengthen the legs. I made step stools for my both of my daughters almost 30 years ago with this approach that are still going strong. It was one my first real woodworking projects and a great way to learn woodworking.

Here are some pictures. Note that these are angled box joints which are a little more difficult to do but aren’t necessary for your bench.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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Lazyman

2559 posts in 1559 days


#10 posted 10-17-2018 02:01 AM

One more thought…

Many meditation benches are made to be foldable so you can either store them out of the way when not in use or to make them portable. On most foldable designs, they attach the legs with piano or even door hinges. This will eliminate the need for any joinery because the hingle should be strong enough for normal use as a meditation bench. Usually, the angle at the top of the leg is set so that they splays outward slightly when it is unfolded so it won’t collapse while in use.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Spikes's profile

Spikes

71 posts in 217 days


#11 posted 10-17-2018 03:33 AM

I keep being blown away by the feedback on this forum, joining lumberjock has made getting into woodworking so much easier and pleasant, thank you all. In no particular order:

@lumberingon this (and links like this) are where I got the idea of thinning the glue for a first pass before the final glue up: https://woodworking.stackexchange.com/questions/840/gluing-end-grain . It seems very reasonable and to match the detailed description of the issue as explained by @jamsomito , which I’m going to next…

@jamsomito, really appreciate all the time and effort you put in offering such a thorough answer, I know from other forums/areas where I help that it’s not just a 5 mins thing, so thank you. I’m convinced by the argument, however going back to my original question – how do I size the dowels and their number? how can I know if 2 dowels are enough or really 3 or 5 are required? and how long? the one in the leg could be anything from just half inch to maybe half of the leg.

@tonys, lovely joint, I see some potential inconveniences for the user, but I guess they are questionable especially if the mortise was on the leg as to avoid anything sticking out on the top where people would sit.

@Lazyman , really nice woodwork, I guess I could try my hand at that box joint, altho I’ve been struggling to make things really precise, but the only way forward obviously is practice. Also stretchers are a problem with meditation benches as it would impede the movement of the legs underneath or if I made them too thin I’m not sure it’d help… again another question of sizing I have no good answer for… how big should the stretchers be to be useful? and yes I’m aware of hinges, but wanted to avoid them for now.

again thank you all,

Spike

-- Don't worry about making progress, worry about practicing. If you practice you will make progress even if you don't want to.

View Lazyman's profile

Lazyman

2559 posts in 1559 days


#12 posted 10-17-2018 04:51 AM

Because meditation benches don’t have to handle the weight like step stools do, the stretchers do not need to be as thick. In fact they only have to be thick enough to accept the screw or dowel used to hold them tight against the legs. Most the strength comes from the relatively large glue surface of the finger joints and the stretchers simply provide a little extra rigidity to prevent racking and splaying of the legs. An alternative would be a glue block in the corners formed by the top and the legs. If you glue and screw this to both the underside of the seat and the side of each leg I think it will provide enough extra strength that stretchers are not needed. If you are not ready to tackle box joints just yet, then I think a dado with dowels or screws through the top and a similar glue block will proved the extra strength needed for this application. That won’t be strong enough for a step stool but plenty strong for a meditation bench.

To answer the primary question you first asked, the best approach to learning is to copy proven designs and materials or use plans by experience woodworkers. The best advice may be to go look at meditation benches that appear to be solid and lasting designs and find one that you can do with only a slight stretch of your current skill set. Over time you will develop the intuition to design and build your own.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Tony_S's profile

Tony_S

939 posts in 3254 days


#13 posted 10-17-2018 09:13 AM


I see some potential inconveniences for the user

- Spikes

I should have been more specific. There’s a lot of different wedged tenons in the link.
No inconveniences for the user at all. It’s cut/sanded flush with the top surface of the stool.

Simple, clean and effective for this application.
How do I know? Because I made 4 of them for some ‘lady friends’ ;) who do Yoga.
Nothing like a hot sweaty woman in tights sitting on your bench….Oh my!

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

View Spikes's profile

Spikes

71 posts in 217 days


#14 posted 10-20-2018 04:03 PM

Tony_S, thanks, that makes a lot of sense. do you have a recommended way to cut/sand flush? I don’t have a japanese saw, which seems to be wha most ppl use, and trying to use a file + sander did not work very well, but maybe it’s just my inexperience and lack of skill is sanding (the rap hit the edges and left some marks and the ROS put a bit of a shallow around the tenon).

-- Don't worry about making progress, worry about practicing. If you practice you will make progress even if you don't want to.

View Lazyman's profile

Lazyman

2559 posts in 1559 days


#15 posted 10-20-2018 04:23 PM

A good sharp chisel to carefully pare it away and get it close and then sand it flush. You can also buy a cheap flush cut saw at harbor freight that actually works pretty well. You may be able to one at local hardware stores as well. I would protect the top with some thin cardboard or plastic if you use the saw to avoid marring the surface.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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