Woodworking Techniques – Parnham Fitting

Parnham Fitting.

This is a jointing method that in many small workshops is replacing Dowelling as a stronger more easily achieved joint. This method is credited as being developed at Parnham Workshops; run by John Makepeace in the 1980s. Dowel joints are common in woodworking, however, they require very accurate drilling and registration of the holes. Not only must the holes be at 90° to the joining surfaces but they must be positioned, dimensionally, very accurately and drilled with a diameter drill to match the wooden dowel.

The Parnham fitting eliminates the problem of drilling so accurately, here we only need what an engineer might describe as a “wet slack fit”. The holes can be well oversize, not too wet and slack mind you, but definitely loose. Now we replace the wooden dowel with metal studding. This is threaded rod available at any builders supply in various diameters from 5mm to 25mm and usually in 500mm lengths.

Cut this studding to dowel length and then carefully degrease it in hot soap water. Alternatively use chemical solvent. Then dry fit the joint and if all goes up well see if the inside surfaces can be polished, then glue it up. Use slow cure epoxy – West System is a favourite here – or if you have a small joint Araldite (not Araldite rapid). The epoxy should fill the gap between the sides of the dowel hole and the threads of the studding. The threads give an expansion of the glue area making this a very strong joint. The slow cure allows a longer set up and open time to fiddle with clamps and get it spot on. If the job is pre-polished the squeeze out of glue can be removed with white spirit.