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Kreg joints vs. traditional joinery

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Forum topic by Kade Knight posted 533 days ago 5386 views 2 times favorited 16 replies Add to Favorites Watch
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Kade Knight

54 posts in 538 days


533 days ago

Topic tags/keywords: question

I would like some objective feedback on this issue please. I am in the planning stage of my first dining table. I have no experience in mortise and tenon joinery yet and am trying to decide whether to invest in mortise and tenon tools or go kreg pocket holes. Any insight as to the strength of kreg joints in leg and apron construction? And how about attaching tops to aprons? Do the kreg joints allow for seasonal wood movement like clips do? Thank you for your thoughts.


16 replies so far

View SamuraiSaw's profile

SamuraiSaw

435 posts in 562 days


#1 posted 533 days ago

For something like a table, the only place I’d use the Kreg is for joining the top to the skirt. Elongating the holes will allow for seasonal movement of the top, assuming you’re using solid wood for the top as opposed to plywood. I wouldn’t trust the pocket hole joinery to have enough strength to join the legs to the skirt. Those joints are easily overstressed when moving the table. Depending on the design, I usually augment the mortise and tenon joinery of the legs with a cross brace.

-- Artisan Woodworks of Texas.... www.awwtx.com

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runswithscissors

894 posts in 622 days


#2 posted 533 days ago

Check out Rockler’s “Surface mount corner brackets for table aprons.” Less than $6 for a set of 4. I weld up my own out of 1” channel steel, but their design looks good. I have also made them out of wood. The leg is forced into the open-bottomed V formed by the aprons with hanger bolts. Be careful; the nut on the machine screw threads is powerful enough to pull the hanger bolt right out of the wood. Makes it completely unecessary to mortise, and I think may be stronger. I’d check out your local hardware store or woodworker’s store if you don’t want to mail order.

Although I occasionally use pocket screws, I am not really a fan of them.

View Ted78's profile

Ted78

156 posts in 597 days


#3 posted 533 days ago

I’d second some sort of corner braces. Wood, metal, store bought or home made are all viable options. The pocket screws, along with the corner braces I think would work fine.

On the other hand it might be a great excuse to buy some fun new tools.

With some patience, and a couple of pieces of scrap to practice on, all the equipment you need to mortise the aprons in is a chisel and a mallet.

Of course if I could afford a mortising machine or had a drill press beefy enough to take a mortising bit I’d have one in a heartbeat.

How’s that for a wishy-washy non-answer to your question?

-- Ted

View Loren's profile (online now)

Loren

7230 posts in 2245 days


#4 posted 533 days ago

Pocket screw joints do not substitute for
clips in solid wood table construction. They
do not allow for wood movement.

All you need for machined mortise and tenon
joints is a plunge router.

If you just want a table, make it however you
like. If you want to grow as a wood artisan,
there is skill building to consider.

-- http://lawoodworking.com

View Marcus's profile

Marcus

1041 posts in 617 days


#5 posted 533 days ago

I use both M&T and my kreg jig, and it really depends on the application. If I just need two things held together and dont want to worry much about them, I use the kreg jig. If I am making furniture I want to last forever, I’ll use a M&T joint. I’ve found that lately I’ve been leaning towards the middle ground and use a lot of dowels.

As for using pocket holes to attach a table top, I’ve had pretty good luck doing that with smaller tables such as coffee and end tables. I wouldnt use it on a full out table or desk top though…too much moving wood or the little bit of play there are w/ pocket holes.

View BRAVOGOLFTANGO's profile

BRAVOGOLFTANGO

271 posts in 600 days


#6 posted 533 days ago

I too have used the Kreg joinery methods, along with wood dowels. I’d consider myself pretty well versed with the Kreg system at this point.

I’ve built several projects, from my all Kreg built rocker posted here on LJ, three 40” tall bistro tables w/12 30” tall bistro bar stools to match, coffee tables, end tables, TV stands, Hall Hutches, etc.

I’ve used the Kreg to join the tops (2×6, 2×4, etc) from underneath and they are super strong. I’ve even built a set of 6’ Barber Benches for my Mom’s shop and all the joinery is hidden and brutally strong. Problem with this type of joinery is plank alignment staying flush. Easy enough to clamp it all together, but a flush joint that will not bow when compressed is easier accomplished with dowel joinery, biscuits, loose tenons, etc, ude to the precise exposed top alignment being spot on (if done right of course).

My recommendation would be to use whichever method you’re most comfortable with as you build your skillset. Personally I was burned out on the Kreg jig system.

Thing is, even a simple Kreg jig can be used to build a dining table that looks as good as any other joinery method and it’ll stand up next to supposedly stronger joinery methods. Also, you can use a Kreg for more than just the aprons if you’re experienced.

That said I do love exposed mortise & tenons, kerfed & wedged or even drawboarded, they just show your work, old school look and show a touch of joinery woodworking class in itself.

View David Dean's profile

David Dean

489 posts in 1496 days


#7 posted 533 days ago

Well I would have to disagree with a lot of folks the Kregjig is up there with mortise & tenons , dowels and you dont have to wait for the glue to dry to move on to the next step and I have build dresser’s and other type’s furniture as well. But as they say seeing is blevieing.

View Kade Knight's profile

Kade Knight

54 posts in 538 days


#8 posted 533 days ago

Great group of guys! Thank you for all the advice. At this point I think I will start experimenting with mortise and tenon joinery…I like the challenge.

View Rick M.'s profile

Rick M.

3776 posts in 977 days


#9 posted 533 days ago

I’ve never used corner braces on any of my tables and have never seen them recommended (except this thread) in conjunction with mortise and tenons. Just make full size tenons (not stubs) and you’ll be fine. Sometimes I pin them with a dowel from the inside.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

View pintodeluxe's profile (online now)

pintodeluxe

3265 posts in 1410 days


#10 posted 532 days ago

For a dining table, you will have too many exposed joints to use pocket holes – unless it is just a simple 4 legs with aprons design. Anything more elaborate than that, and M&T joints work better. The shoulder of a large tenon is great for resisting racking forces.
Honestly I use pocket holes, biscuits, dovetails, and M&T frequently. The more arrows in your quiver the better.

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

View runswithscissors's profile

runswithscissors

894 posts in 622 days


#11 posted 531 days ago

I don’t use corner braces in combination with m & t, in case there was confusion about that. In fact, I repaired loose legs on a (garage sale) coffee table using corner braces, but the hanger bolts pulled out too easily. Finally dug into the matter more deeply, and discovered existing m & t joints that were no longer doing the job. With those joints, there was very little wood left, and the hanger bolts had almost nothing to hang on to.

Let’s see if I can explain what I did: I made a kind of through bolt with an arrow shaped head. This arrow point was a narrow section (about 3/8”or so wide) of 3/4” angle iron, with the shaft a piece of 5/16” threaded rod welded into the V. Drilled all the way through the leg from the hole in the corner brace, mortised the outside corner of the leg so the “arrow head” would lie flush, and bolted her up. I’m waiting on the other three legs until they go wonky.

It’s not a thing of beauty, but does have a sort of “industrial chic” charm, if there is such a thing, and I expect that leg to last longer than the rest of the table.

View TCCcabinetmaker's profile

TCCcabinetmaker

925 posts in 952 days


#12 posted 531 days ago

Loren if you are using the right screws, then the holes made by a pocket hole bit are larger than the diameter of the screw, and if you have the jig setup in the correct way, the hole goes through… So yes wood movement is allowed for. However you do need to be careful to decrease the amount of moisture that can penetrate into the wood, I finish the bottoms of my tables to decrease wood movement, and well no call backs yet.

While the Kreg jig is a fairly new invention, pocket hole screws can be found in many old pieces, it’s just about the same as toe nailing something….

Rick, you don’t have to have the corner braces with mortise and tenon, but they add significant strength to the corner.OF course that also depends on the style of the table as well, there are other things that can increase the leg strength as well.

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

View TCCcabinetmaker's profile

TCCcabinetmaker

925 posts in 952 days


#13 posted 531 days ago

Oh, and I really do respect Loren’s approaches, they are vastly different from my own because of the different ways that we have learned this craft and it is always important to listen to people who do things differently in case the way you learned to do things does not work in another situation, I do respect Loren, just don’t agree with him on this one ;)

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

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GrandpRas

9 posts in 461 days


#14 posted 461 days ago

I just read another blog where the author argued for the superiority of certain wood joints. His opinions were justly supported by testing done by Wood Magazine and other sources on the comparative strength of various types of wood joints. A very brief summation finds him to be adamant on the supremacy of mortise-and-tenon and dovetail joints and highly dismissive of butt joints, pocket hole joints, and biscuit joints.

I do not dispute the facts in measuring the comparative strengths of different joints. What I do challenge is the contention that because one joint is inherently stronger, then for that sole reason, it is the best joint to use. If this were the sole criteria in selecting a joint, then woodworkers everywhere should abandon their saws, chisels, routers and all means of wood oriented tools for a mig welder and welder’s helmet – for a properly welded or mechanically fastened steel joint is exponentially stronger than a wood joint of any type.

But let’s remain with the medium of wood. The author I refer to cites a test done by Wood Magazine one a mortise-and-tenon joint: “ it took 4,733 lbs/force nearly 2½ tons to pull apart.” This is just shy of the average weight of a mid-sized car. Impressive, but it leads me to the questions of:

1. What are the average daily stresses a joint needs to withstand to remain functionally viable?
a. Wood expansion/contraction
b. Shear strength
c. Racking strength
d. Compressive strength
e. Etc.
2. What is the impact of the total project design on individual joint strength

The first question assumes the inherent strength of a joint by itself to resist the various average stresses that would cause the joint to fail. Clearly, in the joining of only two pieces of wood together, some form of physical union (mortise-and-tenon, dado, tongue-and-groove, etc.) is inherently stronger than say a butt joint alone. However, few woodworking projects contain just a single joint. Most projects require multiple joints and in casework, there are at least 4 joint surfaces (open faced, no back). In other instances there may be a number more joint surfaces: cabinet back, face-frame, corner blocks, and a host of other joints controlling racking, twisting and compression. Racking a cabinet that uses only butt joints and glue, but with strength mechanically magnified by construction points of a back, face frame, and corner blocking provides considerably greater strength than racking an individual butt joint alone.

It is not that I would recommend a butt joint for all joinery, but it does illustrate the argument of functional sufficiency. At what point does it become unnecessary overkill (strictly from the strength of project point of view) to use other joints that are demonstrably stronger, but may not be necessary in meeting average stresses of even abusive daily use? I would argue a project using wood joints capable of withstanding a drop from a 3rd story is significantly overbuilt.

By all means, promote true craftsmanship, artisan aesthetics, the reward of demonstrating special skills in various advanced joint techniques, but a premise to build contended solely on the criteria of joint strength is arguably of limited merit.

View Rick M.'s profile

Rick M.

3776 posts in 977 days


#15 posted 460 days ago

I built a cabinet with pocket screws and construction adhesive. Some time later realized we didn’t need the cabinet so I removed the screws thinking the butt joints would just snap apart. With 230 lbs at my disposal, I couldn’t budge the joints. With leverage the plywood splintered inches from the corner, the glue held. Eventually I just cut the corners off with a saw. Point being, those butt joints may have been less strong compared to other joinery but I can’t say they were weak by any measure.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

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