Reffc
Established Member
Interesting video which dispels the myth of end grain joints being the weakest way to join timber.
There are a few things of note though and often end grain joints are made along the long axis where bending moments or shear may be greater than on the short axis, allied with end grain joints always failing on the glue bond. This is explained by the grain fibres themselves being stronger than the glue joint when running lengthways (hence failure at the glue plane). However, the thing of note is that glue is usually stronger than lignin resin in the timber which bonds the cellular wood fibres together, so side grain joints usually fail on the timber, not the glue line, which perhaps explains why the myth of side grain joints being stronger has existed for so long. (ie timber fails before glue joint). The consideration here though is that it's comparing failure forces that should be considered, not whether a joint fails on the glue bond and it's proved from these fairly scientific tests that failure forces of comparable gluing areas results in end grain joints being stronger than side grain joints.
The other take-away (if you watch the 2nd video in the series) is that end grain mitre joints are also inherently strong requiring usually little or no reinforcement. Note in this case that end grain mitres involve bonding of end and side grain so side to side mitres will fail before end grain mitre joints due to greater relative area of lignin bonds. Also, the perception of un-reinforced mitre joints being weak has much to do with relative gluing area and applied moment of long lever arms such as in picture frames where the relative bond area usually comprises a very small cross section of joint.
The final consideration when comparing failure forces is the timber itself. Oak, for example, would be expected to have higher failure forces on end grain joints due to the large grain pore (fibre pore) area compared with closer grained, smaller fibre pore area grained timbers.
I thought it worth posting after considering discussion from another thread where there was mention of end grain mitres.
The decision to reinforce joints by taking advantage of additional strength gained from exploiting inherent strengths of long fibre axis combined with increased gluing area will depend on applied forces in use and for general cabinetry of smaller boxes, plinths or similar constructions not subject to large failure tensile forces mean that no further reinforcement should be needed. The other thing of note is that care to ensure clean and well aligned joints is important.
Video link below:
There are a few things of note though and often end grain joints are made along the long axis where bending moments or shear may be greater than on the short axis, allied with end grain joints always failing on the glue bond. This is explained by the grain fibres themselves being stronger than the glue joint when running lengthways (hence failure at the glue plane). However, the thing of note is that glue is usually stronger than lignin resin in the timber which bonds the cellular wood fibres together, so side grain joints usually fail on the timber, not the glue line, which perhaps explains why the myth of side grain joints being stronger has existed for so long. (ie timber fails before glue joint). The consideration here though is that it's comparing failure forces that should be considered, not whether a joint fails on the glue bond and it's proved from these fairly scientific tests that failure forces of comparable gluing areas results in end grain joints being stronger than side grain joints.
The other take-away (if you watch the 2nd video in the series) is that end grain mitre joints are also inherently strong requiring usually little or no reinforcement. Note in this case that end grain mitres involve bonding of end and side grain so side to side mitres will fail before end grain mitre joints due to greater relative area of lignin bonds. Also, the perception of un-reinforced mitre joints being weak has much to do with relative gluing area and applied moment of long lever arms such as in picture frames where the relative bond area usually comprises a very small cross section of joint.
The final consideration when comparing failure forces is the timber itself. Oak, for example, would be expected to have higher failure forces on end grain joints due to the large grain pore (fibre pore) area compared with closer grained, smaller fibre pore area grained timbers.
I thought it worth posting after considering discussion from another thread where there was mention of end grain mitres.
The decision to reinforce joints by taking advantage of additional strength gained from exploiting inherent strengths of long fibre axis combined with increased gluing area will depend on applied forces in use and for general cabinetry of smaller boxes, plinths or similar constructions not subject to large failure tensile forces mean that no further reinforcement should be needed. The other thing of note is that care to ensure clean and well aligned joints is important.
Video link below:
