The first one i successfully made was from a stainless steel cap screw i purchased at our local Ace hardware for $.40 plus tax. The last one i made was purchased in a package of 100 on line for $.20 including shipping. The first successful one took about 8 # 69 high speed drills @ $.85 each to finally make a hole, plus i threw away at least 6 screws with pieces of broken drills in them.

So far i have learned to use cobalt drills not high speed steel drills. Cobalt drills cost me about $3 each instead of $.85 each. The cobalt drills can drill more than one hole, but they don't last forever. Stainless seems to be fussy about what one uses for lubricant, and has led me to invest in 2 different brands supposedly good for drilling stainless. Both of these lubricants work better than the mineral oil i tried initially.

It turns out, if i hold my mouth right, and have enough of the correct lubricant, and use expensive drills, i can make a vent liner for a few cents. It also turns out that one could ruin several cap screws, and break several drills, and not have made one good vent liner. Making vent liners seems quite silly to me.

In my possession are several Lehigh vent liners, a few PR vent liners, and some home made stainless steel vent liners with 0.028", 0.029", and 0.032" flash holes.