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... with the intention of using the 1" bench-top belt-sander to roll the edges ... but was quickly poo-poo'd due to the plastic melting from the friction , and I really needed to construct a jig to accurately pull it off , ... :
more work 
so I just went back to the file and 400 grit sanding stick
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it's getting there ..
then the plan is to cut these ' bolts ' to the depth of one and a half the depth of the hole and solvent weld 2 together while rotating the joint to avoid cementing the joint solid :
:

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