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Squaring the Fence on a Board Shear

Submitted by admin on Fri, 05/31/2013 - 00:00
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by Bill Minter

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Over the years, I have heard that binders will use a carpenter’s square to test the squareness of the fence on a board shear. While this may work, there is another way that should be more accurate, at least when one considers mathematics, and specifically geometry.

Take a large, approximately 18″ square, sheet of thin cardstock, such as 10 pt. or 20 pt. map folder stock. Align one edge to the fence, make a cut and identify that as #1. Align that #1 edge on the fence and make adjacent cut #2 —you are obviously cutting in a clockwise rotation with the most recent cut along the fence:

Continue cutting each edge making certain that the newly cut edge has been aligned perfectly to the fence. After the 4th cut, align that edge to the fence and re-cut #1. Rotate the cardstock to compare the squareness of the new cut #1 to cut #2. IF every corner is in fact an exact 90-degree angle, the #2 edge will align PERFECTLY with the bed blade. IF there is a slight difference, the amount out-of-square will be 1/4 of that total amount. If you want perfectly square cuts, the fence should be adjusted accordingly.

Iron-Top: If your shear is an Iron Top, such as the Jacques Bookbinder’s Shear as shown in the GBW Blog, the fence is easily adjusted; loosen the large knob a small amount and simply tap on the fence with a hammer to make the adjustment. When adjusted, the fence can be secured again. To hold the fence better, you could add a small C-Clamp at each end. The fence should be checked from time to time for accuracy.

Wood Top: If your shear has a wooden top, there are two things to consider:

First: Make certain that the fence, the metal bar, is perfectly straight. Some bars could be slightly bowed, which will create a major problem when trying to cut material square.

Second: In most cases, the fence is likely secured with wood screws that could loosen over time. Also, the bar could move through normal use, as well as from the expansion and contraction of the wood due to changes in humidity. Adjustments might be difficult if the holes in the fence are too small. And the use of wood screws may not be sufficient if the hole in the wood has enlarged.

An alternative to the wood screws is to replace them with bolts that are threaded into a “T-Nut” that is recessed in the underside of the wood. This modification requires a little up-front carpentry, but the result will allow the fence to be secured tightly. Note that the bolt hole in the fence should be large enough to allow adjustments.

Obviously, a square fence is a vital part of any board shear. The maintenance of your shear will show in the end results—Keep that Fence Square!

Protecting the surface:

The work surfaces of shears have been treated in a variety of ways. Some might be the original, plain, cast iron that can easily rust; while other shears with a metal surface may have been painted and that paint might be wearing away, thus exposing the bare metal. If the surface is wood, it may have been sealed.

With the metal tops, some binders will regularly clean and treat the surface with butcher-block wax. In other cases, the surface may have been covered with a sheet of polyester film—”Mylar”—with the edges taped down. An alternative is to use “Frisket Film” which is a plastic film with a low tack adhesive on one side. This film can be easily removed from most surfaces without leaving a residue. One brand is available from Graphix Plastics in Cleveland, Ohio ( While one type is a soft, polypropylene, the other is a 1-mil polyester film. Polyester is a much tougher film and should stand up to hard use.

Safety Device for Clamp:

A safety issue with the board shears is the clearance under the clamp for the paper or board. There have been a few reports where people have severely pinched a finger and that has caused a close examination at a couple of university binderies. There is a simple solution and this will be addressed in an upcoming supplement in this blog.

May we all have a safe and well-maintained board shear that cuts paper and board perfectly square