Wepster

good to know, when you do it, you should do a tutorial, post it on Youtube. I never had a pair, my cousin did, he was quite proud of them. OP, would love to see your step by step on your flip flops!

how long does inner tube material (I would truck tire inner tubes to be thicker) last as an outsole? No doubt, great straps. When I was young, the hot thing (for about a year, which I suppose is long for a hot thing) was a sandal, made in India, sorta flip flop ish, except there was a loop for the big toe in addition to the thong. Supposedly made of water buffalo, you were supposed to get them soaking wet and wear them so they would conform to your feet (Late 1960s).

I've read in a book I bought, "The Sandalmaking Workshop" by Rachel Corry, that other brands of soling material are Soletech, Ultra, and Birkenstock. Typical flip flop soles are often ethylene vinyl acetate (EVA), sold in sheets or sometimes large foot shape pairs. I have seen replacement shoe/boot soles on Amazon. If you google shoe repair, cobblers supplies and the like you will find suppliers who sell outsoles. And, of course, old tire treads. Long used in Mexico (and I am sure a lot of other places). I saved some old utility trailer tires (replaced just due to age, so lots of tread) expressly for this purpose. Though honestly, I probably never will, not enough years left in me for the all the back burner projects.

Might not be quite want you want, and perhaps you have already explored this.... similar to waxed. here is a link to a search.. https://search.brave.com/search?q=diy+tin+pants&source=web

Again, this may or may be helpful........cleaning vinegar has about 9% acid, and you can buy concentrate - I got some on Amazon https://www.amazon.com/gp/product/B091FZRT1X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 plain old white vinegar is mostly water, as you noted only 4 or 5% acid.

this may or may not be helpful... in another craft, it is called ebonizing wood. Here is the first reference I found, search it, it is very popular (since ebony is very expensive!) https://www.popularwoodworking.com/finishing/ebonizing_wood/

You might consider a CBN wheel, depending on what you are sharpening. I think (not 100% sure) they are best on HSS, carbon steel may clog them, thought they sell SlickStick that helps prevent that.

I am so tempted. Crusty bread? We have several outstanding bakeries in Syracuse for wonderful crusty bread! Their black pepper and cheese is to die for, as is their rosemary and garlic, yum. Just wish we had a good deli.... But I so do not need the machine, I am out of space for the hobbies i have collected. Table saw, small band saw, little drill press, bigger drill press, 2 little lathes (don't ask) one medium lathe, several sanders, a 2x72 belt grinder, a sand flea, Singer featherweight, a Pfaff zigzag (Mom's circa 1968ish) a newer Brother, tons of books, boots ( I really like boots) etc etc.... I am nearly 70, I have lots of stuff!

HI, I am new, this may be inappropriate here, maybe a mod will move it to where it belongs (in the Gateway to Airguns forum, there is a spot for bargins you spotted (they call it Bargin Gate), so you can share with others who maybe interested). I have no personal or financial interest in this, just thought someone might be interested NYC area used Singer 29-4, $300, I just got a chinese leather patcher, have no room for this, otherwise I would drive the 4+ hours to Brooklyn to get it! Added bonus, swing by 2nd Ave Deli in Manhattan for Pastrami! https://newyork.craigslist.org/brk/atq/d/brooklyn-singer-29-leather-sewing/7574473510.html