Over the years I have gone through a lot of 2-stroke lawn trimming machines. Each time the power head failed I would go back to Home Depot and buy another. I also bought extra attachments like a sidewalk trimmer, leaf blower and hedge trimmer. Those extra attachments were simply transferred over to the new head.
This past week I saw a click link weed whacker at Walmart for $80 with a 3-year replacement guarantee and without checking first, bought it. When I got it home and went to trim the sidewalk I realized that attachment had the reverse gender from what I had already accumulated.
This was my fault, I already knew there were 2 varieties of the Ryobi style click link lawn tools. The ones sold by Sears and Home Depot had reversed gender so you couldn't use the competitors products with each other.
Rather than buy replacement attachments, I decided to make an adapter.
Step 1: The Parts Needed
The closest fit for a steel sleeve is 1" emt. I have scrap pieces laying around, so I cut off a piece about a foot long. 1" electrical conduit is a little bit slack, so I used the rounded end of a ball peen hammer to dent the tubing to make it snug inside. This way I didn't need to split the pipe and use hose clamps to tighten it.
I needed to couple two ends of 1/4" square shaft together, so I used a hexagon threaded rod coupler. The inside threads were 1/4" x 20. I drilled out the center with a 1/4" drill bit and then broached the ends with a carbide made from a #2 Phillips speed bit. Most speed bits are 1/4" hexagon and inexpensive. I have plenty to spare. I held the bit in locking pliers and squared it off on a bench grinder then hammered it in to each end of the coupler to broach a square hole for each side. I didn't go all the way through with the broach because this would allow the coupler to slip off one end. If you have coupled PVC pipe you know the coupler has a ridge in the middle inside so each piece only goes halfway. Same idea.
Because both the tool and the head had spring loaded buttons, I drilled a hole for the tool and made sure it was secure, then marked the head shaft with a permanent marker 6 inches from its end to its button.
Then I assembled the set and aligned the tool and head so I could trim the sidewalk with the throttle down and measured back to where the second button hole should be drilled. With both ends buttoned down, I can't rotate the head once the pair are assembled. The line trimmer end that came with the new head had a screw clamp that allowed the pair to rotate, but the clamp is a permanent part of the tool end.
The adapter stays on the tool. Before I assembled the set I hammered the coupling down on the tool side shaft so it won't fall out when I take the pair apart. If I want to use other attachment I'll need to make a coupler for each in order to be sure it fits snug and the alignment is correct. With both ends buttoned at least it won't take tools to swap ends.