strength of dowels

[HowardH]

I am planning to build a new permanent workbench out of 2x4 or 6's and noticed a lot of the builds on youtube are based on M/T joinery.  That would be fun to do but I also have a Mafell DDF40 which will allow me to use up to 1/2" dowels each drilled 40mm into the mating work pieces.  It's extremely precise as well.  Would that size dowel provide enough strength to be used instead of the M/T to keep it from racking under a load?  I figure I can get up to 4 dowels per joint. 

 

[ChuckM]

Hard to tell since the size and the structural components (aprons, stretchers, shelves, etc.) are unknown. For an average bench build with proper design, I'd say 1/2" dia. dowels as described are strong enough.

 

[HowardH]

It's not going to be that big.  thinking 24" x 50".  I also have two MFT's as well for glue up's and cutting. 

 

[Cheese]

As a fall back position, you could substitute 1/2" diameter aluminum rod for the wood dowels. Then the issue is no longer the strength of the dowels but rather the strength of the dowel pockets.

 

[Rob Z]

Hey there Howard

I don't have much experience with dowels other than taking apart old doors that were built with dowels. One place I would look is the website for Dowelmax.  The owner has a lot of videos and you might see one that recreates what you need to do and that might help you.

I just looked at the Mafell site for that machine you  have.  [smile] Nice !

 

[HowardH]

Hey Rob!  Good to hear from you.  I have a Dowel Max and it works great. The DDF40 is lot more versatile.  With dowel sizes from 3mm up to 12mm, it's like having a domino and domino XL in one machine. 

 

[Rob Z]

Howard, that's an impressive range. 3 mm ~ 1/8" ! Have you ever used it for a dowel of that size?

 

[ChuckM]

It's not going to be that big.  thinking 24" x 50".  I also have two MFT's as well for glue up's and cutting.

In that case, good to go.

Here's one strength comparison between dowels and Dominoes:=323

If I recall correctly, the test performed by Fine Woodworking, however, had the opposite conclusion.

 

[Michael Kellough]

Dowels would be fine for positioning parts but with all the racking a bench experiences (if you use it for planeing) I’d want more glue surface than you get with dowels.

But, dowels would be fine if you combined them with the large Kreg pocket screws intended for 2x stock. The screws are 2-1/2” #14 truss head and make an extremely strong joint.

 

[ChuckM]

To handle racking, even M&T joints alone would not be enough if there're no other structural components to support them, a point I made in my first post. I do not think that pocket screws are at all necessary to supplement dowels or Dominoes, if the bench is properly designed. Here is one of the many examples people can find:
https://www.dowelmax.com/dowel-jig-system-projects/how-to-build-a-diy-workbench/

The devil is in the details which the OP has not provided.

 

[CeeJay]

I’ve used big (30mm x 60mm x 50mm) through M&T and bridle joints, and then put two 1/2” dowels through each joint for my workbench.

It’s not going anywhere. It weighs 130kg.

Sent from my iPhone using Tapatalk

 

[Bob D.]

YT has a number of comparison tests between dowels, dominos, m&t, pocket screws, etc.

Here's one

 

[Birdhunter]

I also own the Mafell DD40F machine and admire its quality and precision. To me, I think the 1/2” dowel construction is OK if the mating surfaces are large enough to defeat racking pressures. The main drawback of the DD40F is that it is slow compared to. Domino machine.

If I were building this structure, I’d pull out my Domino 700 and put some honking large tenons in the joints.

 

[HowardH]

I plan on making the legs out of tripled up 2x4's planed to 1.250" each so that should give me plenty of stock around the dowel holes. I have a Kreg pocket hole jig as well so I can add a few screws for some extra strength.