Wood magazine joint testing

[drumpriest]

Jim, I mostly agree with you. As I posted in the poll thread, I use pocket screws routinely for face frames when you cannot see the back. I don't think face frames typically receive all that much stress. It's not as if you are building a ladder.

I mentioned there that all they really do is hold doors or are spacers between drawers. Even the doors though, much of that stress is being helped by the cabinet body to which the FF is glued. I think that the real lesson here is that all of these options have merit for that type of application.

It's not a totally useless joint test, of course, as we learned more properties about mortise and tenon. Already suspected that they were the best, but now we know that pegged tenons arn't necessarily any better.

I have been using double biscuits on some frames, and I feel the strength is more than adequate. I've stood on the joint and it didn't budge.

[JimD]

Keith,

I also wrote a note to Wood that was a bit more blunt. I wish they had tested in the other direction, tried #20s in the 3 inch wide stock, and provided more information on the dowel joints. Their shear test tells us something about racking resistance but I cannot think of a situation where that is very important. On a cabinet, the back, not the face frame is what I depend on for racking resistance. On a door, racking is typically only the weight of the door that creates stress. The opening and closing action would be more a shear on the flat side of the door which was untested.

I also noted to Wood that they had done a good job on mortise and tenon joints. I also asked for more information on the dowel joints like the type of dowel, whether it was grooved, how they drilled the holes, etc.. They obviously got some pretty good dowel joints so I'd like to know more what they did. I have made some pretty bad dowel joints before despite using dowel centers and a doweling jig so it would be nice to know a bit more. Maybe a reason I like biscuits better than dowels include the facts that I rarely make face frames (I build almost exclusively frameless cabinets) and I am better at making biscuit joints than dowel joints. I use pocket screws some but I think they are pretty crude (but effective). I like my dedicated mortiser and it has caused me to make more mortise and tenon joints.

Jim

[drumpriest]

I'm a big fan of mortise and tenon, especially loose tenon. For kitchen cabinets, I think pocket screws are just fine. I also agree with you about the sheer stress. Unless I have all of the drawers out of the chest, and a kid tries to climb the FF like a ladder...

Also, all of these tests show incredibly strong joints.

[lcm1947]

Well I for one was somewhat shocked at the results. I sure thought biscuits would be the second strongest. I was somewhat surprised and disappointed that pocket screws didn't do as good as I'd been lead to believe though and I guess equally surprised how well dowels did. WOW! what a surprise read. Very interesting to say the least. I still like my pocket holes though. Althought I am now for the first time ever considering buying a dowel jig.

[rickd]

I'm not that surprised that dowels came out ahead of biscuits in the Wood Magazine tests at all. I use both dowels and biscuits but always choose dowels over bisuits for joints that are going to be subjected to any stress. No surprise to me that the M & T joints were first as that has been pretty much accepted by most woodworkers as the strongest - if done properly.

"If done properly" is the thing that leads me to sometimes use my dowel jig over M & T. I have a Dowel-Max jig that makes perfectly aligned dowels easy to make. The joints come out perfect with no measuring or special procedures - it's fast and easy.

Until I get much better at making M & T joints, I am convinced that using my Dowel-Max jig will give me a stronger joint than my inexperience with M & T will produce. To me anyway, that's as much the solution as anything else. It isn't always what is the strongest joint but what does your expertise and equipment allow you to make that will be the strongest for you?

That's why I agree with what JimD said earlier about wishing that Wood had mentioned how they made their dowels and if they used a jig and, if so, which one. I know we've had this discussion here before about the relative strength of each joint and different tests have seemed to result in different answers.

I use all three methods depending on the situation. I still need a lot more practice and experience with M & T before I could say they are the strongest joints I could make. But, I agree with the findings of Wood's test that M & T are the best.

[lcm1947]

I have been thinking about this articule and think I may have stumbled across something. In the pocket-hole test it doesn't appear that they used glue. You can see the glue in the dowel test but it sure doesn't appear to be any glue on the pocket-hole test. If that is true that would make a lot of different I'd think and sure would screw the results up.

[Jeffrey Schronce]

That's why I agree with what JimD said earlier about wishing that Wood had mentioned how they made their dowels and if they used a jig and, if so, which one. I know we've had this discussion here before about the relative strength of each joint and different tests have seemed to result in different answers.

They should have disclosed all their test information. Brand of glue, application method (did some joint surfaces get more glue?), brand of all biscuits, dowels and machinery, etc.

[onedash]

Tom Silva busted out a dowelling machine once that looked just like a biscuit machine. Instead of a blade though it had two drill bits. Everything else appeared identical. lined the two boards up drew a line, lined the index line up drilled two holes in each board and stuck in the glue and dowell.
If I had that I might use dowells.

[Stytooner]

I learned how to build faceframes using a horzontal boring machine. They make short work of drilling for dowels and as long as you get good with the alignment, you can really pump out the work. Your layout is very critical, but is so with any jointing technique.
Using dowels by hand is only for the brave oir skilled.
For things like faceframes that really see very little stress once finished, any joint including a but joint would be sufficient as long as it was a good glue joint.
Chairs and heavy tables and work benches are usually what requires the very strongest of joints. These are typically the M&T. Bicuits and pocket screws can certainly speed a projuct along, but when all is said and dry, it is the glue thats doing the holding over the long haul. At that time you could even remove the pocket screws if you wanted and still have a strong joint.
I think the key to good joinery is in the glue work and not necesarily whats in the joint unless the joint requires high strength ie.. chars and tables.

[drumpriest]

Lee, I agree with you about it being the glue. I often use pocket screws in unseen locations as clamps. They hold the thing together where it would be difficult or inconvenient to rig up a clamping solution.

[niki]

When I was living in Japan, I made many drawer units (Tansu) and show lockers, all of them with dowels.
Part of them was transferred with me. They went on the sea for 6 weeks from Japan to Israel and when I moved to Poland, another 4 weeks on the sea (in container).

Excluding the “unit up – unit down”, they went through 3 different climate zones (Japanese summer has 95% humidity, In Poland, at the winter we have less than 20% because of the heating).

After 8~10 years since I made them, I don’t have any signs of fatigue, cracks, or splits in any of the glue lines (Titebond).

Considering my very low knowledge and skill at that time (just beginning), the dowel connection must be very strong.

During the time, I developed very precise doweling method on the router table, no wear of bushings and very accurate and clean holes. Oh yeh, and very fast.

niki

[cgallery]

During the time, I developed very precise doweling method on the router table, no wear of bushings and very accurate and clean holes. Oh yeh, and very fast.

niki

Have you outlined your router table technique somewhere so I can learn about it? I use a number of doweling jigs that I'm pretty happy with, but I'd love to hear about a router table method.

-Phil

[Stytooner]

Dowels are very strong. I think the reason that wooded joints are preferred and are stronger than actual butt joints is the amount of glue surface is increased. Dowels, biscuits and spline or M&T all benefit from the extra gluing surface. Pocket screws don't, but they have an added benefit of being semi adjustable until the glue dries. They also have fair shear strength unless you are using under 3/4" stock. Then the screws needed are too short to do much good.
Any good glue joint should actually withstand the climate changes Niki mentioned. Congrats on those joints. Titebond is the magic word there. Thats stuff can turn an ordinary rats nest into a stronger rats nest.

[niki]

Phil
I also made a few jigs but all of them involve bushings. With the router table no bushings and the accuracy is amazing.
Everything is documented and I’ll post it but first I have to post my very unconventionally crazy router table.

Lee
Nowadays, I’m using the Polyurethane glue that is known in USA as “Gorilla glue”.

Although it requires long “clamping time” (3~4 hours), It gives me an “Open time” of 30 minutes so I don’t have to rush and I can check and correct the “squaring” in a more relaxed way (very important for amateur like me).

niki

[Stytooner]

....and that stuff can turn a rats nest into a canoe.
That is some good stuff. There is a learning curve to taming a Gorilla, but once conquered, it will be your friend.

I know all too well about needing more play time when gluing. Chess boards can eat up the clock when trying to clam them up. Especially so when it's hot like where I live.