Sunday, March 3, 2013

A Simple Vector Clamping Repair

NOT a simple Vector Clamping example

When a client presents a job, I always take the time to fully explain every detail of the work that needs to be done and then, if they want to do it themselves, they can make that decision.  Part of the reason I do that is to educate the consumer, and the other part is that I would be happy if they decide that they want to actually do it.  For whatever reason, over the many years I have repaired furniture, very few clients make that decision.  In the end, they are always happy to pay me to do it.

When it comes to gluing curved surfaces, I need to explain that it is necessary to make clamping parts which they will never see, just to hold the clamps in the right position.  Often they note the hundreds of different clamps hanging on the wall near the bench, and they conclude that it will take that many to do the job.  However, as I explain the reason I need to make these special shaped wood clamping parts, I point out that, properly done, the joint can be pulled together using only one clamp.

The "secret" is that that single clamp needs to put pressure directly perpendicular to the center axis of the joint face.  On a straight break that is simple.  On more complicated breaks there may be several different faces and all the vectors need to be considered, so several clamps will be required.

In the past I have posted photos of this type of clamping.  Recently I posted a picture of a chair for the "Why Cuban Mahogany?" post.  In these photos there are many clamps and it may be difficult to easily understand which clamps are doing what.

In this post I selected a very simple repair.  This project is a lyre shaped mirror support for a late Victorian bureau.  It is made of walnut with a face veneer.  It broke at the weak part of the grain.  The break is fairly straight and clean, and it has not previously been repaired with synthetic glue.  I think it is a clear example to illustrate the Vector Clamping procedure concept.

First I determine a line (vector) which is perpendicular to the center of the break.

Second I cut some wood clamping parts of a wood that is softer than the walnut, like pine or poplar.  These parts have "legs" which allow them to be attached to the walnut in the right position, and a "purchase" for the clamp to sit, directly in line with the vector.

Third, I use plexiglass on each side of the repair to keep the faces flush.  The plexiglass doesn't stick to the glue and allows me to see the joint as I work.  I apply warm Old Brown Glue and the long clamp which pulls the joint together perfectly.  I grin as the glue squeezes out evenly on all sides, indicating my calculations were correct.  After the joint closes, I apply a final tightening of the plexiglass clamp.

It is so easy, when you know what you are doing, that even the client could do it.

1 comment:

Anonymous said...

It took me some time to really grasp the concept of vector clamping, but after studying the examples, here on the blog posts, then taking the concept to my workbench, and doing some real world mock-ups, I finally got it.

Will the face veneer be patched after the break in the mirror support is fully cured, Or left as is?

The old adage holds true, you can really not have to many clamps!