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“Stitch” welding helps minimize heat distortion

This repair to light-gauge steel on a swather frame required careful welding and some fabrication effort

In this Shop Class instalment, we tackle a repair to a swather frame. The draper belt rollers on this model install on a short pin that sits inside the front of the frame. But over time, corrosion had weakened the relatively thin steel that held in one of the pins.

When the bearing inside the draper roller seized, the pin, which was now rusted in place, twisted out of the frame. The damage made it impossible to just install a new pin. The frame had to be repaired in order to accept the new part.

You can see the problem in Photo 1. This new roller pin, which supports the bearing on the front of the draper belt roller, should just fit into a key-shaped slot in the frame. But because the original pin was rusted to the frame, it began to twist when the bearing seized. It then ruined the portion of the frame where it mounts. We now need to cut out the damaged section of frame and weld in a replacement with a new key-shaped slot to hold the new pin.

Note the rust holes in the lower right of the image. We’ll cut that section out, too.

In Photo 2, you can see that the damaged section is now cut out; we used an air-powered cut off tool to do the job. If you look carefully, you can see a vertical and horizontal line drawn on the frame, which will help us correctly position the slot for the roll pin when we install the patch. This will ensure the draper roller will still run in its proper position after the repair.

We used the piece we cut out of the frame as a template to create a repair patch, as shown in Photo 3. To create the key hole, we used two hole-saw bits and drilled into the steel. A rotary Dremel tool was used to finish the slot opening, which merged the two holes together into a keyhole shape.

The next step, Photo 4, was test fitting the repair patch. It will be welded into place using a butt joint, which meant it had to fit tightly into the opening. The gap in the lower right corner was a little wider than we hoped for. But with a little extra care, it can be filled with weld.

Note how the roll pin now lines up with those positioning lines we drew on the frame with a Sharpie pen.

Because the steel used in the swather’s frame is slightly less than 1/8-inch thick, we don’t want to cause any heat distortion when welding in the repair patch, so we’re “stitch” welding it in. Stitch welding simply means we’re using a series of short tacks. Running a long, continuous bead would warp the metal. We’ll work around the entire joint and slowly lengthen each tack until the joint is fully welded.

After grinding the weld bead smooth with the surface and spraying a little paint on the bare metal to prevent rusting, the repair is complete. †

About the author


Scott Garvey

Scott Garvey is a freelance writer and video producer. He is also the former machinery editor at Grainews.

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