1/2" oak dowel in 1/2" hole - pretty tight - might it split?

[Greg Guarino]

Oak 1x2 to wrap around a desk surface. I've got some oak 1/2" dowels that I'm going to use both for decoration and to keep the 1x2 in line with the desk surface while the glues dries. Maybe not strictly necessary, but I like the look and the 1x2s weren't 100% true even though I picked the best ones I could find. (I bought those before I asked for the lumber store advice BTW)

Anyway, I've already drilled the holes, I'll probably glue it up tomorrow (Sunday). I made a test piece out of an oak 1x2 scrap. (It's quite a test piece, by the way, with a couple of lap joints, a narrow groove down one edge, a rabbet on the other, 2 or 3 different finishes and now two dowels).I used a 1/2" Forstner bit which made nice clean holes. But I found I needed to pound the peg in with a rubber mallet. It went in OK, but it's ^tight*.

I cut off the excess and even sanded it down for practice, but I didn't use any glue. Is the addition of glue likely to swell the wood and crack the oak 1x2?

[Father Haskell]

Turn the dowels so their grain is at 90 degrees to the grain of the 1x2's.

[Greg Guarino]

Would that be because the dowels will expand perpendicular to their grain (i.e., the growth rings will widen) and the 1x2s will have more strength lengthwise? Or perhaps because the 1x2 and the dowel will then swell in orthogonal directions?

In any case, is what I described OK to do? Or should I have either made the holes a hair larger, or sanded the dowels a little? Is a tight fit, requiring a mallet, normal?

Funny thing: On my test piece I drove in the dowels with no thought to their orientation. One was nearly parallel, one nearly perpendicular. I was trying to decide which one I preferred, strictly from a visual perspective. Now I have a better reason, I guess.

[John Grossbohlin]

The grain orientation as suggested by others is the right way to handle this.

I wonder if the tightness is due to dimensional changes in the dowels and/or holes due to the gain or loss of moisture, i.e., one or both are no longer truly round. Pushing the end of the dowel through a dowel plate to insure roundness, and drilling the holes just before plugging, might help this situation too.

John

[RicodJour]

Unlikely unless you're using a lot more glue than you need. A little dab will do ya. You could use a CA glue if you're worried.

A bigger worry is that you had to pound the dowels in. Tapping them in with a mallet is one thing, pounding is another.

If they're both from the same species, why is there a need to turn the dowel so the grain doesn't align? Same species, same coefficients of expansion for both radial and tangent.

R

[Greg Guarino]

For better or worse, I glued it all up this morning. I did put the dowels in with the grain perpendicular to that of the 1x2s.

I'm not sure what word to use. To my ear, there's some room between "pounding" and "tapping". If I were being precise, I suppose neither word would be quite appropriate. It was tight enough to make me wonder about it though.

How long, I wonder, before I don't have to worry about it anymore? It's been glued up for about 2.5 hours. No cracks so far. Am I out of the woods yet?

[Greg Guarino]

Hadn't thought of that, and I don't have such a tool. But that sounds like a good explanation. The doweling may very well have expanded in the bin at HD. I thought about chucking the dowel material into a drill and sanding it down a tad, but it the end I didn't bother.

and drilling the holes just before plugging,

The test piece that made me wonder about this was indeed drilled moments before I put in the dowel. It was already tight.

[Pete S]

I'd ask:

- How sharp was the drill bit?

-Was it a brad point, or a regular twist drill?

-Or a forstner bit? A dull bit might have to push its way through. A regular twist drill might, too.

-How fast did you drill?

-A forstner bit would be my choice for an accurately sized hole in this case. Pushing the drill bit real fast through the wood might make for a poorly sized hole.

-What was the real diameter of the dowels? Could they have been a little oversize or out of round?

There are times when I go looking for a metric bit that is slightly over the nominal size if I want a looser fit. Case in point for oversize holes: Making a wooden drill bit index. I'd go

1/64 oversize for each hole.

Pete Stanaitis

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[dadiOH]

You were out of the woods as soon as you put it/them in.

[RicodJour]

If you are planning to seal the wood and it's in a relatively stable environment, you don't really have anything to worry about. Well, unless you plan on living a really long time. And even then, just call the cracks patina and everyone will be awed. ;)

For a test, throw a micrometer on the dowel and see how out of round it is. Notice I didn't say "if".

R

[Greg Guarino]

Brand new,out of the package. The test hole, which was tight, was the first use for this bit.

Forstner.

Not fast. Slow, even.

That is the likely explanation, I'm discovering.

Since it doesn't seem to have cracked anything, I'm happy with the look of the tight fit. But next time...

[DD_BobK]

I'm not sure I agree with the desirability or need to "turn the dowels

90 degrees", not thinking it through completely, it seems like it doesn't matter.

The hole in the 1 x 2, depending on the moisture content when the hole was drilled, will either grow or shrink in the transverse direction (perpendicular to the long axis of the 1x2) but will remain relatively unchanged in the long axis of the 1x2.

The problem with using dowels is that their radial, tangential & longitudinal axes cannot all be matched up with the same axes of the piece of wood receiving the dowel.

The way to get all the axes of the "dowel" to match up with the receiver is to cut a plug from a piece of would with the same grain orientation as the 1 x 2.

Unfortunately, plugs have very reduced "shear" strength when compared to traditional dowel. :(

So one has to choose.....

match the axes & eliminate differential movement and accept the poor "dowel" strenght maximize dowel strength and accept differential movement.

cheers Bob

[RicodJour]

A 1/2" dowel will move a miniscule amount regardless of orientation. Unless, of course, someone is soaking the wood in water. I see no benefit to changing the grain direction.

In the OP's situation I would have used screws to obviate the need for clamps, and used contrasting wood plugs. Maybe a nice endangered wood species. ;)

R

[chaniarts]

1/2" dowels frequently aren't.

[whit3rd]

Often a good choice, but for glue in the hole, a brad point might suit better (the hole sidewalls can get burnished by the Forstner, and that inhibits glue adhesion). I always scuff up dowels on coarse sandpaper (50 grit) when I want 'em to hold glue, too.

If your hole is tight, and glue is applied, it can seal and your driving of the dowel will make a hydraulic piston. It can blow the wood out right then and there. If that didn't happen, the water in the glue will help the oak 'relax' any stresses, and it's all OK when it dries.