Dowels and Tenons

mike marvel

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So. Florida
Tenons and created dowels that are of a close fit make for good mating when glued. If you notice that the prefabricated dowels that are sold have a very slight chamfer on the ends, and could have flutes, or spiral grooves.

If you cut a dowel from dowel rod, and leave the ends just cut with a sharp edge, and drill a matching hole, when inserted, will scrape the sidewalls of glue and push it to the bottom of the hole. In addition to that, if the fit is that tight, that action can be compressive, in that it not only pushes the glue (which is like a hydraulic compression), it compresses the air. In this instance, you may experience the dowel not wanting to move into the hole, and if it does, will be forced upward out of the hole. This can make clamping ineffective to impossible.

The slight chamfer on the ends provides for a 'feeder' lead, allowing a smooth insertion, and minimizing getting caught on any grain, and reduces the 'scraping' of the walls. The flutes and spirals allow for glue and air to escape allowing the dowel to go into the hole without having a glue amount to collect towards the end of the dowel.

When applying glue the first third to half of the hole will be scraped, pushing the glue to the balance of the hole and what is excess will collect at the bottom. So, not much glue is needed on the bottom third of the hole, except for a light coating. Having the depth of the hole slightly deeper than the reach of the dowel will allow for what gets collected at the bottom.

Likewise for tenons, I got into the habit of a very slight chamfer on the lead edge, and some 'escape' grooves on the face of the tenons for glue and air. Looking at this tenon, you can see how sharp the leading edge is. If the mortise for that tenon is a very close fit, the tenon can have the ability to be restrictive and react as a smooth dowel would do with respect to compressing glue and air when mating up.


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i have learned about the fluted dowels and to make some room for the tenons like you mention and show, the hard way, when you try to close a joint and the glue is on and then it wont close and you have glue all over, say bad words but that doesnt fix it. doing as mike has shown does.
 
Good points Mike.

For dowels, I made a block of wood with several different size holes in it, in which the holes were ~1/64" larger in diameter than the dowel they were made for, i.e. 17/64" for a 1/4" dowel, etc. Then I hammered a nail through the side of the block into the hole so its point protruded into the hole ~1/32"-1/16" depending on the size of the dowel. Then I would drive a length of dowel shaft through the hole to score up its side, doing this a couple of times ~ 180° apart. After this I would cut them up, chamfer the ends & drill the dowel hole a touch deep as you noted above. Works well when you don't have any ready made dowels on hand.
 
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I flute my dowels by crimping them gently with the serrated jaws of a pair of pliers. Fast and effective.

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Good points Mike :thumb:

I learned awhile ago about chamfering the tenons. Makes life easy.

I was lucky enough to be given about 500 1/4, 5/16, 3/8. and 1/2" fluted dowel pins many years ago. I know it's overkill but I use them on almost every panel I glue up instead of biscuits.
 
Thanks Mike for taking the time to explain all that info.
I had observed the flutes on dowels but never thought of it being applied to tenons. Thanks will try store that in my head for next time. Where were u when i went to school. My shop teacher did not know about doing this for tenons. :)

sent from s4
 
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