What's the deal with dowels

[hummingbird]

I've been making molds and forms and have been using dowels to help align layered pieces. Ive bought dowels at home depot and the Canadian equivalent Rona. Why is it that the diameter of a dowel is never what is labeled on the dowel. It's usually bigger than it says. For example I'll need a 1" hole for a 7/8" dowel. Sometimes there's no perfect bit size for the dowel and I have to sand it smaller. Nobody that works in these stores seems to know anything about it. Am I missing something?

[kencierp]

Most of the time I find that the dowels are a tiny bit over-sized --
so I have drilled a few common size holes in the cast iron top of my table saw -- I just tap the dowel through the holes and they are shaved down to the perfect fit. I believe the Woodcraft and other store sell a die to do the same thing.

[hummingbird]

That's a good idea Ken. I just can't understand why they just don't make them the right size in the first place.

[johnnparchem]

Ken's method will make dowels. Make a square rod that is a little bigger than the diameter of the dowel, and start tapping the rod through the largest hole in the die or Ken's table saw top that the rod will not fit though and continue with smaller and smaller holes until you are at the right diameter.

Saves a trip to the big box store if you only need a few for a jig.

[kencierp]

I believe the quality problem is just wood being wood -- the humidity thing, natural expansion and contraction changes the size (most likely continually) so its a bit of a moving target. Matter of fact when constructing with dowels I use a water based glue anticipating that the dowel will expand in the hole changing a tight fit to a force fit.