Dowelmax -- dowel size guidlines

[Ray Schafer]

Can anyone give me some general guidelines on what sizes of dowels to use with various sizes of wood?

For example -- I want to use dowels to assemble a wall cabinet (like an upper kitchen cabinet). I will use 3/4" plywood. Which size dowel should I use?

Thanks.
Ray

[Lee Schierer]

Dowels should normally not be larger than 1/2 the thickness IMO. They are also a lot of work to use and don't provide much added strength, though they will help with alignment if done properly. If you are looking for added strength use screws or splines.

[Ray Schafer]

Jime Lindsay sent me this information:

Any 3/4 material whether wood, plywood or MDF, I always use the 3/8 inch dowels and a small artist's paint brush to coat the inside of the holes with the glue, and for a really robust joint, a bit on the exterior of the dowels too.

If it is long panels, I do 2 dowels every 8 inches (approx.) using the distance gauge. If however you are drilling into the face of the wood, don't forget to alter the drill stop to drill 5/8 into the face of the wood and 7/8 into the end or edge of the other plywood work piece. Give an extra 1/32nd inch for clearance.

I use the 1/4 inch dowels for smaller jobs (it is still quite strong) I use the 1/4 inch set up mainly for raised panel doors and also drawers using 1/2 inch faced plywood.

[Ray Schafer]

Lee,

If you look at the threads about the Dowlemax, you will see that there is a lot of informaiton around that indicates that dowels can provide a lot of strength. I also have found them easy and quick with the Dowelmax. I can actually put together a carcass quicker than with the pocket jig, and I don't have to worry about alignment.

Not trying to start another "Dowelmax vs. other techinques" thread since that has been done already.

Thanks for your comments!
Ray

[Lee Schierer]

Lee,

If you look at the threads about the Dowlemax, you will see that there is a lot of informaiton around that indicates that dowels can provide a lot of strength. I also have found them easy and quick with the Dowelmax. I can actually put together a carcass quicker than with the pocket jig, and I don't have to worry about alignment.

Not trying to start another "Dowelmax vs. other techinques" thread since that has been done already.

Thanks for your comments!
Ray

I've followed those posts with interest. I'm not buying the advertising done by the manufacturer based on comparative test data on joints from reliable wood magazines. See the link. Wood joint strength (http://www.sawmillcreek.org/showthread.php?referrerid=5960&t=79559)

[Ray Schafer]

I definitely respect your opinion. I think that the dowel joints -- using as many dowels as I choose on a given joint -- are strong enough for my purposes. I am not going to try to convince anyone what to believe on the point of what is actually stronger.

Thank you for adding to this thread.
Ray

[Will Blick]

Using hidden joinery in sheet goods is always a quandary...

I too am NOT trying to start dowel vs. domino thread, but in this case I think there is some differences. At least when the joint will subjected to heavy loads (of course "heavy" is relative term here)

IMO, in most cases the dowel or the domino will be more than strong enough, but sometimes the loads on the joint may be extreme and you want the strongest joint possible. In such cases, it seems common sense that the domino is better suited for this job.


The reason is..... a round dowel with a diameter half the thickness of board, reduces the integrity of the wood as only 1/4 of the wood thickness remains above / below the dowel. So while the dowel may be stronger than the break point caused by the load, it seems the dowel has created a new weak link in the wood.....specially MDF.


Hence why I think the Dominos are the right tool for the job, as they provide more lateral joining area while keeping more of the boards original strength above / below the domino. Here, the dominos longer width vs. height makes it ideal for sheet good joining. Of course, Biscuits fit this scenario as well, but have much less strength than a domino....

Anyone agree?

Of course, in the case of a bookshelf, where the force will only come from one side, I would think lowering the dowel is a good option to combat this inherient shortcoming fo a round tenon with thin sheet goods, i.e. when the dowels diam. is near half the sheet goods thickness.

[Will Blick]

shameful bump

[Chris Padilla]

In my experience, it isn't as simple as "A is better than B". Every situation is different, the materials are different. Plywood to plywood or hardwood to hardwood or hardwood to ply...MDF anyone? :) Are we talking butt joints or edge joints? End-grain to long-grain? I think you get the point.

In the case of a typical kitchen cabinet, whose carcass is usually made of 3/4" plywood, one doesn't tend to find many butt or edge to edge joints. In those cases where such a joint is needed/necessary, I think biscuits or dowels or dominos do aid with alignment and strength. In the case of a typical box, I think dados and grooves to be of value and hardwood faceframes to tighten it all up (again, how you attach the faceframes).

In the end, modern glues are stronger than the wood itself so use whatever aid you need to to ensure a good glue joint (biscuits, dowels, dominos, clamps of various flavors, pocket screws, nails, hand pressure, etc.) and you're likely to have a strong joint.

[J. Z. Guest]

Replying to Will Blick's first post.

I disagree. The Domino would add the same weakness, except over a longer area.

Also, you're forgetting that we usually use several dowels in a row whenever there's room. In that case, the weakness you point out would be more in the Domino, because with dowels, there is full thickness wood between the holes.

In practice, according to the WOOD magazine test a while back, Dowelmax joints are stronger than Dominoes. This is an independent test, not a sponsored one. I believe it was a fair test, since they used as many Dominoes or dowels as would fit in the joint.

[Ray Schafer]

I think the answer to which is stronger or better is "it depends."

[Chris Padilla]

Replying to Will Blick's first post.

I disagree. The Domino would add the same weakness, except over a longer area.

Also, you're forgetting that we usually use several dowels in a row whenever there's room. In that case, the weakness you point out would be more in the Domino, because with dowels, there is full thickness wood between the holes.

In practice, according to the WOOD magazine test a while back, Dowelmax joints are stronger than Dominoes. This is an independent test, not a sponsored one. I believe it was a fair test, since they used as many Dominoes or dowels as would fit in the joint.

Jeremy,

Do you have the particular WOOD issue info handy? I subscribe so I'm sure I have it.

[glenn bradley]

Like many things in our world it does indeed depend. The dowels in plywood will at the least provide some alignment. Biscuits may be quicker for that. I think we have all seen "production" kitchen cabinets and they hold together a surprising amount of time despite their quality. I just had a pantry shelf fail after 20 years. Two little brads finally pulled their way through some particle board . . .. amazing.

[Ray Schafer]

Lee,

Thanks. That is a good guideline for me to use.

Ray

[Chris Padilla]

A brad is just a small dowel, Glenn! ;)

[J. Z. Guest]

No, but I found it by searching their website. I scanned it before I threw the magazine, so I have the article at home. I'll try to remember to post it up here later tonight.

[glenn bradley]

A brad is just a small dowel, Glenn! ;)

I just blew coffee on my monitor! :D

[Bill Huber]

To answer your question I would use 3/8 dowel.

I bought another bit and stop, I set one for the face of the wood and then the other one for the rest of the length of the dowel. I do make test holes in both to make sure the holes are at the right depth.

[Ray Schafer]

I did the same thing -- get another bit and stop ... that works really well. I also bought some extra stops (at the Borg) so that I can use them for things like my shelf hole drilling jig. They are really handy.

Thanks for the pointer on the dowel thickness.

Ray

[J. Z. Guest]

Jeremy,

Do you have the particular WOOD issue info handy? I subscribe so I'm sure I have it.

Chris, it is in the July 2007 issue, and the article is called "Loose Tenon Tools."

From some of their photos, it seems like they only tested double dowel joints. It also seems like more dowels could have fit in the same joint. (at least 3 or 4)

If that were the case, DM may have won out over the traditional M&T. Who knows.

[Chris Padilla]

Thanks for finding the info, Jeremy. I'll have to dig up that issue.

I think dominos and dowels and loose/floating tenons are all stronger than trad M&T joints. The main reason, I believe, is because glue is present in both mating pieces because each mating piece gets a mortise and glue. The trad M&T joint only has one mortise and therefore only one side gets glue.

I think beyond that, dominos, dowels, and loose/floating tenons will all be plenty strong and it doesn't matter which of the 3 beats the other.