Here is some sketches/photos of my Adjustable Curve Jig and Tool Grinder.The curve jig is made of a base of 1/2" plywood 12 feet long 18" wide. It is strengthened by 2 1/2" high by 3/4" stringers every 18" and length ways to add a little stiffness to it as it was constructed from 4' x 8' sheets.. A 1/2" plywood backboard is fastened to it 4 1/4" high. (could be thicker). The height should be a little more than the tie thickness.Two hardwood strips (I used Elder), 6 foot long, 3/4" wide by 1 1/4" high are fastened by one end to center of the backboard by two 1/4" flathead screws and tee nuts. The screws are spaced 1" and 2" from the end. Next a chalk line was snapped the length of the jig for reference. The offset for the curves was marked out every 6" starting from the center. I used two curve radii - 40 ft and 80 ft. The actual curve offset marked is the curve radius + 1/2 tie length since the hardwood is the outside guide for the ties. Holes are drilled in the backboard and the hardwood strip every 6" for
screws. Aluminum Links 1/8" thick by 1/2" wide are drilled to accommodate
the screws. There are three holes per link - 40ft R, 80ft R and Straight.
These links hold the curved hardwood strip in the exact position for the
selected curved which is marked out on the base. Links are not required
at 0 or 6" points. The first 4 or 5 links are slotted since the holes
are close together. The backboard screws are 1/4" - 20 hanger bolts
and hold the links with 1/4" wing nuts. The screws in the hardwood
are 8-32 and screw into a hollow aluminum post press fit in the hardwood.
[they are actually post screws used for holding paper pages together -
I had them on hand, any suitable screw would work.]
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