So, when using a frame with a rear dropout incorporating a derailleur hanger, but not using a derailleur (SS, fixed gear or IGH), I see bikes often with just to hole sitting there -- or, worse, hacked off. So, I was thinking, is there an alternative? What comes to mind is a place to mount a taillight, even if in many countries it is on the wrong side (I'd think from 50' away or more, still readily visible). A bracket should be straightforward enough to fabricate -- but attaching it? My old Sutherland's guide says a Campagnolo hanger is 10mm x 26TPI, close to 10mm x 1.0; so is that a M10-1 bolt? Like for instance BOLT ? Anyone try this? Or, I guess, try to locate an unwanted Velox RD and cannibalize the mounting bolt.

Chain-tensioner for a freewheel machine with double front rings.

Streamers?

Good spot to mount a chain cleaner.

or a 1st aid kit for reattaching fingers chopped off attempting to re-mount a dropped chain on the fixie.

The empty hole bugs me too, I always thought there should be like a chainring bolt, maybe with a tiny reflector attached.

But not really a concern for me as I will never have a 1 speed/fixie anything so....

Derailleur hangers never bothered me on SS builds. They're out of the way and relatively inconspicuous.

Brazed-on shifter bosses, on the other hand, are completely unacceptable and a non-starter for any SS project.

Which has nothing to do with this discussion. I'll move along now.

I have drewed off shifter bosses - on a beater fixie... it was an appropriate look.
Nicer conversion got some jewelry.
The derailleur hanger stayed though, on all of them.
You could probably figure out a way to mount a light or action camera to it though. Not sure what else it would be good for.

Alternate response, in an attempt to offer something useful:
Instead of repurposing the hanger, just get yourself one of these oh-so-sexy White Industries freewheels to divert your attention...



Ooooooohhhh... shiny!

Still not comfy with what bolt would be a best option. And on eBay, a used Velox RD with the nice bolt (red "C" center) starts at $40, a lot for just a bolt.

That sounds so 1930's in terms of aesthetics! I like it; presumably a tensioner comes with a mounting bolt.

So that got me looking at chainring and other crank bolts online -- alas, none seem to be M10. But it was worth checking!

I could imagine a clever engineer could devise a backward-swinging kickstand to mount in that hole. On urban bikes -- curb feeler?

Shiny is always a winner. My current project is IGH so I don't need a freewheel, the sprocket is shiny silver but not exceptionally so. I am just not sure I want to drag it off to the chrome $hop.

Great idea for countries where they drive on the left hand side of the road. The market would not be insignificant

https://www.google.com/search?q=m10+...hrome&ie=UTF-8

Coffee grinder mounting point.

On the derailleur hanger when not using a derailleur, I agree that an empty hole does not look finished. Just filling the hole with a decent looking plug would be better than an open hole and repurposing the hole for something like a light might be a good solution.

If you were a machinist with a lathe, making an aluminum screw that is 10mm diameter with a 26 tpi thread should be doable. You could just cut a screwdriver slot in the head or get fancy and broach a hex into it. Then polish the aluminum to make it look like it belongs. But that is a fair amount of work for this endeavor, unless someone sets up to make a batch of them, and then how many could they sell? I'd love to have some just in case I ever need it, but with the cost of making an almost bespoke part and shipping, I don't know if I'd spring for it.

Then there is this hole cap from McMaster Carr. Metal Snap-in Panel Plugs

They are made for a 3/8" hole but should be able to fit a little larger hole at .394" , or at least that is what I'm thinking. I'd get the 9563K261 with nickel plating and for a thicker panel (like a derailleur hanger). Bending the tabs would enable it to fit the 10mm hole. This would look more finished than just an empty hole. Of course, you'd have to buy 50 of them for $16 plus shipping.

Hmm... First thing to come to mind is a Suntour S1 chainrest.


Second thing that comes to mind:
truck nuts

But seriously, most rear axles will be m10x1. You could take one from your pile of broken rear axles and use that along with whatever hardware you need. Doesn't everyone have a pile of broken rear axles from all their friends who refuse to give up freewheels?

Too weak; it'd bend.

Put in a classy earring. Maybe a pearl or even a nice stone with some facets.
Aside from that, it's a bad location anything other than a derailleur or a chain tensioner.

It looks like "M10x1.0 plug" gives better search results than "M10x1.0 bolt". Plenty of choices. But who wants a box of 50, or just one but $15 to ship?

Aah, aluminum would be lighter than steel, and you could polish it. Presuming you just wanted to fill the hole and not try to attach anything there. But I just bookmarked at Amazon a steel one, shipping weight "0.01oz" so I guess that would not make a bike to much heavier.

I suspect that's true. Probably also true for "flag mount".

Many of those links like Grainger have nationwide locations who sell over the counter. A lot of the AL ones appear to be Rice burner tuner shops. Any metro area should have some of these motorsport tuner shops.

I'd be inclined to find a smooth head, slotless "locker" bolt for it. There also are friction-fit automotive type plugs if you prefer plastic over metal.