While building a couple rockers the other day I got to pondering a thought,(ya it hurt a bit)…
Would pocket screws be strong enough for the front and back rails? I would still use m&t on the sides but I’ve been using dowels on the front and back rails.
I’m considering through mortises on the back of the chair at the rails for strength and looks.
I know dowels add vertical load bearing strength but might not 3 pocket screws do the same? It sure would speed the process up a bit.
Edited 4/4/2008 7:50 am by jagwah
Replies
Pocket screws would be strong enough to hold. Will you be able to hide them, though? Personally, I wouldn't use them, but not due to strength.
Chris @ flairwoodworks
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
Pocket screws can make very strong joints, but hiding them can be a problem. I've used the store-bought plugs that are available in different wood species, but they definitely don't disappear. At best, they just fill that elongated screw hole.
Edited 4/5/2008 10:31 am by Dave45
Pocket screws have their place, but rocking chair construction is not one of them. Wood magazine a while back did a test on all the different joinery and pocket screws did not fare very well. For non-load bearing face frames and other nlb applications they are great and fast. Your idea for through M&T joints is by far the strongest for that application. Floating tenons were rated higher then dowels.
>> Floating tenons were rated higher then dowels.
I didn't see that article, but I don't understand why a dowel would be intrinsically weaker than a floating tenon. They seem like the same beast to me, except for the shape of the tenon. Certainly there are applications that call for a rectangular shape (resistance to twist), but I don't see that making a difference for the rail of a chair. What am I missing?
MikeTo the man with a hammer, all the world is a nail.
The problem with dowels is that when a dowel is inserted perpendicular to the grain (into a frame stile or chair/table leg, for example), there is virtually no face-grain/face-grain surface contact, which is where most of the strength of a glue joint comes from. Dowels excel in "grainless" materials like MDF and particleboard.
-Steve
The jest of the article was all about gluing surface, long grain not endgrain. All the joints that performed well had the greatest amount of face grain surface area. The strongest door frame joint was a open M&T then an end lap. The strongest drawer box joint was a finger or box joint, through dovetails were much stronger then blind dovetails which were one of the weakest box joints, go figure. A nailed and glued rabbet was stronger then a blind dovetail. I am still making all my drawer boxes with dovetails. The locked rabbet was a very strong joint so was the sliding dovetail, I guess all that Chinese furniture must have it right (haha) I saw a Thomasville piece (end table) this weekend stamped under the drawer Made in China and it was awful. The gluegun is alive and well in China.
How bout drawbores? Were they covered. thinking about using them in places in a rocker i'll be making for my daughter in law.
Tom
The article did state that pinned M&T joints were no stronger then normal M&T's and some cases were weaker because they eliminated some of the tenons surface area. They did not test a drawbore, but for chair making they have been used for hundreds of years with great success. The trouble with a drawbore is getting the offset slight enough to not tear the tenon, but enough to keep it tight. I have never used drawbores in making a chair, but don't some people use them without even using glue. The conclusion was that with today's glue and accurate equipment we can make joinery pretty exact and some of our commonly held myths might not be a true as we think. I was crushed about the weakness of dovetails, oh well, I am still going to use them. Myth Busters-Love it.
I guess drawbores were use extensively in the days before strong glues, and held forever even without glue. I'd like to see a test done with a mt with the best glue, against a drawbored one with no glue, making time part of the equation. I think I know which would win.
Tom
Hi jag ,
Nice looking chairs you made the other day ,
While I am and have been a advocate and user of pocket screws for around 25 years or so and do use them on my face frames , a chairs structural integrity should have some joint work involved .
Otherwise we could just use metal corner brackets and such . A chair especially a rocker gets as much stress as you can give .Imo the M & T then dowels would be stronger and a better application in this case .
The pocket screws say 1/8" of steel has more tensile strength then a 3/8" dowel , but the dowel has no pulling power , both have there places .
Whichever joint you use , I have always backed my corners up with a substantial corner block , glued and screwed as insurance , even if the glue in the joint went a way the corner block would hold in most cases.
dusty,
Sorry for the slow response to everyone's great help. I've been on the road taking this chair to my daughter and new grandbaby in LA.
To the question and your responses. While I agree dowels have good purpose for this type of construction and MT may even be better,my choice, I wasn't sure the use of pocket screw from a vertical stress point of view. I felt the screws like some have said would hold well as screws do they might not have enough shear strength to support a person.
The esthetics of a pocket screw hole within the seat framing is not a biggy. Many fine furnishings made have a, "non pretty side". I was just pondering the comparative strengths.
With all your helpful thoughts I'm going to back off on the idea of pocket screws and just do MT and through MT's and I'm going to beef up a few areas.
While loose MT's are stronger in most circumstances there not going to work on the crest rail or mid rail . I learned I shouldn't laminate the crest rail and mid rail since it weakens the tenon. I'm going to steam bend these parts.
Thank you all. Oh and no matter the construction the best work I've ever done sat in it yesterday holding her baby and my grandchild Dario.
With everyone indulgence I present
Mom and Dario
View Image
Edited 4/7/2008 11:35 am by jagwah
That is why we build furniture when we retire. It is our legacy for our family to enjoy. I have built, and will continue to, more stuff for my kids and grandkids then for our house. Aren't grandchildren the BEST!
They offer the best of inspirations.
A local auction house sent me pictures of a coming auction and that chair was among the pieces. I immediately thought how my daughter would love that chair to rock her new baby when it comes. We won the bid at $45 and brought it home.
Unfortunately the rocker was in a lot of distress. But I liked it so much I was inspired to build the chair and several more using it as a pattern. I'm modifying some of it's connections as I've said in earlier post.
So from an inspiration for my daughter comes another to support my old age. Whenever old age comes of course!
"I wasn't sure the use of pocket screw from a vertical stress point of view. I felt the screws like some have said would hold well as screws do they might not have enough shear strength to support a person."
I think that a lot of decks are build with screws, if that's any comparison.Chris @ flairwoodworks
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
Chris , It's not a sheer strength problem as far as the screws won't break , the wood will give way and the screws can pull out especially with a fine thread ff screw .
This joint just needs a more better way .or maybe longer coarser screws ?
dusty
or maybe longer coarser screws ?
And there's the rub.
There really isn't much material where the dowels go to use a longer coarser screw. And your right it's also the small remaining amount of wood under the PC that will give way. Logic then says PC's are more for a static not active use.
I use PC's a lt on my custom cabinets but cabinets don't move under stress with stress at joints.
jag , Exactly , you caught it .
It was really a tongue in cheek remark , kind of my idea of some strange form of humor maybe .
But I do share the idea of application and function dictating design.
When I design a new kitchen for clients I ask how they will use the kitchen and get the info to contour a room to order that I know will fit the needs of the home owners .Usually when we get to the actual drawings or plans they know it will work because we already thought out each challenge.
dusty
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