by Jon Elvrum
What are the proper clearances to observe when boring dowel holes?
1. The distance from a dowel edge to the edge of a panel should not be less than the dowel's radius.
2. When drilling into the end of a board, plan for 2/3 of the dowel's length to be inserted. When inserting into the face of a board, target 1/3 of the dowel's length. If wet glue is used add 1 mm to the bottom of each drilling. Because of a cantilever effect, the dowel strength is increased. If you use pre-glued dowels (water activated) this additional depth is not required.
3. Use straight flute dowels, not spiral dowels in sub-strater panels such as MDF or particle board. Use spiral grooved dowels in hardwood. There are illustrations available in a past WOODWEB article (you can find it by searching the archives on the phrase "dowel"), and in a Custom Woodworking Business article titled "System Drilling" (published last year).
Jon Elvrum, Director of Distribution and Sales at Ritter Manufacturing in Antioch California, is also a well known author and consultant to the cabinetmaking industry. He has written numerous articles on the 32mm cabinetmaking system and production woodworking in general.