For getting cables and wire through the firewall, I like the idea of the doubletree ball pass throughs, but they?re a bit spendy. Seeing as how I own a lathe, and a milling machine, I was thinking of making something similar, since I have the stock around, and just have to take the time to cut it. I was thinking of making a tapered collet, a tapered hole for said collet to nest into, and a cap to squeeze the collet into the hole and tighten it to whatever wire/cable/plumbing needs to pass through the firewall. Slather it in the 3M fireproof adhesive before it all goes together to fill in the cracks. So my idea may be well intentioned, but not work in the real world, so I was looking for opinions here.