I've converted from the CNC Router Parts standard linear motion to linear rails and bearing blocks.
I had a friend mill up two 1" aluminum interface plates that I used to attach the linear bearing blocks to the gantry uprights.
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Once the bearing blocks were mounted to the interface plates and the linear rails were installed, I worked on one side at a time. I removed the bolts holding the gantry upright to the CNC Router Parts linear bearing carriages and then removing the cold rolled steel.
Installed the new linear rail, slide the interface plate on and bolted it to the gantry upright.
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I was also able to move the gear rack up to the top slot on the 80/20 1530 extrusion.
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Two things I neglected to consider...
•The rail stops were too short and had to be redesigned.
•The tensioning bracket wasn't supported. I ended up fabbing a new mount from angle iron.
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One benefit of doing this conversion is that I gained an additional 1 1/4" under the gantry.
I used BLH25F bearing blocks and BLH25Rxxxx linear rail from Automation Overstock.
Happy to answer any questions!