G1nko

I bought a Univega Sportour with Shimano 600 arabesque. It has a Shimano 6-speed cassette where the 14t cog is threaded and serves as the lock ring. This part needs to be replaced as the new chain skips under load. It actually slipped on the smallest 3 cogs, but I was able to flip the other two around. I don't think I can flip the locking cog because it has a built-in flange that serves as the spacer.

I'm not having any luck finding a replacement on the 'tubes but I think that's because I have the search term wrong. What is this part called? Can I flip it and use a shim? I'm guessing I can't use a threaded track cog because of the shim/flange issue... Any ideas?

*Edit: it's a 14t threaded cog, not a 13t

Bill Kapaun

Uniglide threaded cog.

BTW, some fee hub bodies were Hyperglide compatible.

ThermionicScott 

I'd go ahead and try flipping it with a spacer (should be able to use a "bottom bracket spacer", too) -- what do you have to lose?

Otherwise, these are available: https://www.ebay.com/itm/Vintage-Shim...item4172bf02bb

look171

it might be a long shot, but have you check your hanger for alignment? Those little cogs usually do not wear unless the previous rider is a monster.

Bill Kapaun

Try this link-
https://www.loosescrews.com/index.cgi...id=25476274687

RobbieTunes

I'll bet someone here might have one of those cogs....

pastorbobnlnh 

I do. OP shoot me a PM.

wrk101

The smallest cogs tend to wear out first. Check out the prices of NOS uniglide cassettes on ebay, they go high. I usually change out the freehub to hyperglide instead. Then you are free to use current hyperglide compatible cassettes. I understand some of the eary uniglide hubs are not compatible with hyperglide. So far, I have been lucky. I tend to get hyperglide hubs off old mtb wheels.

I just took off a Uniglide cassette on an arabesque bike yesterday. Need to figure out what to do with this one, as it is yet another XL frame size.

The problem with a spacer, is the smallest cog threads on to the hub, and is what holds the entire cog set on.

G1nko

Thanks for the assist. I shot pastorbobinnh a PM. I'm going to dig up a spacer and see if that works also. This bike's not a flipper but for my younger son to take with him to NYU.

dddd

The fastest repair would be to repair the small cog's teeth so as to be compatible with the newer (new?) chain.

The narrow driven side ("edge" if you will) of the teeth develop a bit of "pocket" wear near the base circle, allowing the chain's rollers to run in a slightly more-advanced position relative to the tips of the teeth.
This foreward/advanced positioning of the chain and rollers also increases slightly/proportionally in response to increasing chain tension, due to the elasticity of the chain's elements.
This at some point allows the rollers to contact the driven-side corner of each tooth as the roller would normally fall freely into the space between teeth unimpeded.
The on-the-road diagnosis is thus "failure to engage" (and resultant skipping) under increasing pedaling force.

The repair involves trimming the driven-side corner of each tooth (the corner on the side of the tooth that the chain roller pushes/pulls against).
A </=1mm straight bevel does the trick, angled about 30 degrees to the driven side ("edge") of each tooth.

The whole sprocket can be trimmed in perhaps two minutes, by hand against a grinding wheel.

I've also done the whole sprocket's teeth in just minutes using a 3/8" diameter Dremel stone, with the sprocket still installed on the bike!
I've had to do this a few times, in order to make a far-away ride start after discovering a skipping-under-load problem the morning after assembling a new or revised drivetrain. I immediately circle back to the house, plug in the Dremel and am back in the saddle, riding-to-the-ride, skip-free, in about 5 minutes.

And, in cases of the most minor inclination toward skipping under power, a new chain will break in and adapt itself to a not-so-worn sprocket within just a few hundred miles in most cases.

I just hate to discard possibly still-serviceable parts that are even semi-rare or expensive, especially when the fix is so easy.

old's'cool

dddd's fix worked for me, on some misbehaving cogs. Try to keep/get the grinding dust out of the works!

G1nko

I'm trying to visualize this and I think this is one of those instances where a picture would be worth a thousand words.

old's'cool

I can't argue with you there; however, I don't have any pics and the cogs in question are thousands of miles away from me.
The main point is, if the cog's teeth have a hooked shape, you need to judiciously get rid of the hooked part, i.e. at the outer edge. Not much at stake, it's not really usable as is, so you can only make it better.

G1nko

For the record, I pulled the hub apart again and measured the spacers. They're 3.5mm. I put in a 2.5mm bottom bracket spacer, because there's already a thin shim in there covering the end of the cassette screws, and turned the cog around. Everything runs perfectly now and the bike is off to college in a couple weeks.

RobbieTunes

Glad that worked out.

pastorbobnlnh 

Plus I'm sending a replacement threaded UG cog.