Friday, January 16, 2015

Pinch dogs

In the pic above (1933), an odd double nail is described and intended for joining wood elements for which a classic clamp would be inapropriate. Its name is pinch dog. They have a squared section and a shape with two parallel tips; each tip has a chisel shape, the bevel being toward the internal side. When the pinch dog is driven in the wood, across two parts to be joined, the opposite bevels push them one against the other.    
The dark side are the holes they leave on the wood, so can be better used on surfaces not shown or those to be painted.The pinch dogs are available on online sites and their price is around 3-4 $ each (depending on dimensions)
 So, I tried to build some home made pinch dog, using iron fence staples I took (for free) at my hardware store.
Differently from pinch dogs these nails had not parallel sides, but they work.
The first job was to cut the tips and grind two new inner bevels by a file for obtaining the shape you can  see in the pic above on the right. 
A dozen of home made pinch dogs required half an hour ca.

I had my first try for gluing up a panel.
It will be painted, so no matter for holes.
Being its thickness only 10 mm, this is a case where metal clamps do not work well: the grip surface on the edges is restricted and it is easy to cause distorsions when the clamps are tight; sometimes the panel needs a new flattening job when the glue dries.

One main advantage of pinch dogs is that the elements to be glued, stay simply on the bench; it offers a solid and flat surface for a good gluing up (only you have to protect the bench with papers).

A necessary condition to permit to the nails of working properly is to have perfectly jointed edges, so the planing job must be done carefully. In this case I used my type 7 Stanley #8 (1893-1899), a fast and accurate workhorse.

 Glue up.

When the "pinch dogs" are nailed across two panel elements, the glue squeeze out is evident.

The result is definitely great, the job really easy.

When the glue dries, remove our home made "pinch dogs".

The panel is ready for the next steps.

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