Just looked up the http://www.grizzly.com/products/52-Sheet-Metal-Shear/G5772 Shear.
Those are expansion springs.
I would look into adding helper springs to the foot pedal after you make sure all bearings and joints are lubed and in good shape.

Another thought, Could there be something bent, Say the linkage?

Just thoughts And let us know how you fix it.
Don

Last edited by 2-Ton; 05/17/2018 9:50 PM.
1967 GMC 9500 Fire Ladder Truck
"The Flag Pole"
In the Stovebolt Gallery
1946 2-Ton grain truck
1946 3/4-ton pickup,
1953 1-ton pickup
1957 1-ton flatbed dually,
1954 Pontiac Straight Eight
Of all the things I've lost in my life, I miss my mind the most!