2024 Repair of a Bowl Made in 2017

The 8.6-inch diameter bowl pictured below has a Burmese Rosewood rim and Walnut pattern rings and was made in September 2017.  It has succumbed to several joint failures to the base, a failure mode which often traps the unwary when making segmented work. 

Most of the rings on a segmented bowl sit on top of one another, and so the end grain joints are supported by a very strong side grain to side grain joint from at least above or below, and in most cases both.  So, if the timber humidity changes significantly then the expansion or contraction, which is greater across the fibres, will try to alter the segment angles in the segmented rings.  If this stress cannot be resisted by the weak joint, it breaks. 

One solution to the problem I have seen suggested involves putting a loose disc into a rebate in the base and securing it with two dabs of adhesive at the long grain ends.  I have tried this, and frankly I don’t like it.  I like to have a pattern on the base.

I have stopped getting base failures with patterned base inserts since I started dousing the work in Danish oil on the first two coats and then adding 3 more.  It gives a very good finish, and it reduces the change in internal humidity of the timber in response to an external change.  

How durable that fix is I have yet to discover, but a possible better solution occurred to me.  I have implemented it as a repair on the bowl pictured beneath.  The centre disc is cut in half across its face, rotated by one eighth of a turn, and re-glued together.  This means that all the segment joints in each disc are supported by side grain in the other. The composite disc is then rebated at the edge to fit in a rebate in the body of the bowl.

The work was held by sanding the rim of the bowl flat, and gluing it to a sacrificial block, taking great care to centre it.  This meant I could turn out the base and cut the rebate for the disc.  The base was then finished and attached to a sticky chuck plate, again being careful to centre, I was then able to turn the inside of the bowl and re-finish the rim.  You might think that the sacrificial block was hard to remove.  If you did, you were right, but it was achieved without incident.  It was one of those jobs where you think that any one of the stages could fail or the whole thing fall apart, but not so.  In fact, I am delighted with the result and was disappointed that the original work was flawed, because I have always liked it.

How good this will turn out to be I don’t know yet, and I don’t know if it has been tried before, but it feels right to me.