Raimund

I got a lot of help here to remove, clean and re-grease the freewheel and hub on my c.1995 All-Terrain. All done now. But I had to fix something and I don’t know what it is. I’m calling it a “set screw”. There is a small machine bolt that goes through a hole next to the end of the mounting slot that brings the derailleur onto it’s mounting position atop the freewheel. It goes through the hole and through the end of the mounting slot on the frame for the wheel axel. It is secured with a nut in back real close to the outer gear cog on the freewheel. For me it was quite a job of work but it looks fine. What is the purpose of this little beauty? The only thing I can figure is that it is simply there to prevent the derailleur mounting plate from spinning while riding.

Raimund

Little machine bolt

FBinNY 

I think you're referring to the screw holding the claw to the dropout.

It keeps the claw and RD in place when you remove the wheel.

It also establishes a 2nd point of contact to orient the claw at the intended angle.

I've cases where people had no idea the part had loosened of fallen out until they went to fix a flat and the RD came off with the wheel.

Raimund

Thanks FBinNY. That makes sense. When I took it off I made the mistake of assuming the nut on the back of it was fixed in place. When putting it back together it was nowhere to be found. So I found a replacement that fits. Interesting to know that it is indeed a retaining screw. I put some thread lock on it.

FBinNY 

Just to be sure, it's a special flange nut that engages the slot.

If you're not sure search for a picture of a "derailleur claw nut".

Raimund

This is great. A derailleur claw and nut is exactly what I am dealing with. I just rummaged around to find a new nut, bolt and washer combo that worked. I made the final bolt length “adjustment” by putting a couple of washers under the head of the bolt. There is no slot or anything to house a nut. Thanks much.

Hondo6

You might want to replace that setup with the proper nut. It will hold the derailleur hanger in place more securely and will also likely be less prone to loosening.

They're available on eBay for around $5 plus tax, shipped.

https://www.ebay.com/itm/362000002846

Raimund

Thanks for the suggestion. It’s C$41 including delivery from USA here in Canada on Ebay. I will look around a bit more but it looks a better than this photo now. Took it apart and put on a lock washer that’s a tighter fit.
Universal health care if I fall off though!j

Hondo6

Ouch. Didn't realize you were in Canada. I found what I think is a Canadian postal code near you and double checked - and yeah, that's pretty exorbitant S&H for a $5 part.

Ebay lists some China-made claw-type derailleur hangers that appear to have free shipping to Canada at around $5US. You could get one of those and cannibalize the nut and bolt. It would also give you a spare hanger in case something happens to bend your original hanger.

https://www.ebay.com/itm/404046742273

Raimund

Thanks for digging this out. Good news. I stopped in to my local bike shop to get a new set of cantilever brakes for the rear wheel. He gave me one of these nuts for free out of his box on the bench. Also the Tektro Oryx brakes were C$20. I’m discovering that bike shops, this one anyway, have collections of parts taken off old bikes or older model new parts sitting in the back in case they need them for repairs. Looking online here, the new Tektro Oryx brake model is C$57. Looks pretty much the same. Sexier graphics. It’s not really worth paying a guy to fix up an old bike but I’m finding there are ways to get the job done myself at reasonable cost.

dedhed

that's why I strip nuts, bolts, adjusters, springs, screws etc before I scrap any POS bike. Those parts that are bike specific and overpriced to buy. Probably have 3 or 4 of those claw screws/nuts in stock.