Pulley Screw Thread Size? (SPOILER ALERT)

[cachagua]

I've stumped two of my three favorite hardware stores and a specialty fastener joint. Pray tell, SOMEONE here must know: what is the thread diameter and pitch for rear derailleur pulley screws?

If it helps narrow things down, I'm talking about pre-2000 equipment. I assume there is, or was at one time, a standard, because all the ones I've ever tried to swap were interchangeable -- Campy, Suntour, Shimano, Huret, et cetera. The specific unit I'm working with is a Suntour GPX -- the screw for its guide pulley threads into the lower pivot spindle, and I want to attach a different cage with a flat head countersink screw. I've got a couple of options for drilling, tapping new threads, and using a bigger screw of whatever thread I care for, but that gets me into removing so much material that the attachment may not be robust. I'd really like to match the original threads.

Also if anyone knows a source for stainless screws in this pattern. Thanks in advance--

[choke]

Toronto Cycles says M5....no stainless but they do have Ti ones.

http://www.torontocycles.com/Selling/Derailleur.html

[Tony T]

Also check out Loose Screws (https://www.loosescrews.com)
https://www.loosescrews.com/product-category/drive-train/derailleur/?orderby=price
(5 pages of derailleur parts incl bolts)

This might work for you.
Shimano Dura Ace RD-7400 Rear Derailleur Pulley Bolt
$3.00

https://i2.wp.com/www.loosescrews.com/loosescrews/wp-content/uploads/2015/12/SH-54A1820.jpg?w=640&ssl=1

[oliver1850]

The GPX uses a 6 mm screw with a shank length of 16.75 mm and 6.5 mm thread length. I don't know the thread pitch but it's considerably finer than a common M6 fastener. I will check around and see if I have an RD that's rough enough to demote to parts use.

[cachagua]

They don't seem to be the 5 millimeters diameter/1 thread per mm that we're used to -- what we call M5. The threads are finer. The word one of my hardware stores gave me was they're 5mm x .8 threads/mm. That is, they identified it as such, but didn't have anything that size in stock. So I took that info to another place and got what they said were M5x.8 screws, but they're way too small.

Only now I'm wondering -- is that the correct dimension, but they sold me some other size by mistake?

If it were as simple as using a pulley screw, I'd totally do that -- I've got a dozen. Conveniently, the spindle's already threaded to take one. But what this screw has to do is to fasten the outer cage plate to the lower pivot spindle, so I need this thread pattern, but in a flat head countersink screw, with no unthreaded portion. The head has to be that shape to a) squeeze the plate against the end of the spindle, and b) stay out of the way of the chain as it passes by on the pulley. Probably need about 12mm total length.

I know, I know, why don't I just buy a derailleur. But where's the fun in that?

Edit: Oliver slipped in ahead of me. Okay, so 6mm diameter by some finer-than-usual thread? Alright, I'll pursue that...

[oliver1850]

I only pulled the upper screw initially. It is longer than the lower. Do you need both?

I checked a bunch of other SunTour RDs and none of them used the same screw as the GPX although they are all 6 mm. I suspect the SL RD uses the same one, but I didn't want to take the one I have on my Ciocc apart. Shimano, Campagnolo and Sachs seem to be all 5 mm.

The closest one I found to the GPX was on a Cyclone Mk II. It is the same except for the wrench size and the fact that it's shorter than the top GPX screw. It works fine for the lower. You might get away with using it for the upper but there's not much thread engagement so you'd have to be careful to tighten it enough to stay put, but without stripping the threads.

I found an external hex screw on an Edge RD that's long enough to work, but the head sits above the surface of the cage plate. It might contact the spokes in low gear, so you'd have to be careful setting it up if using it.

[cachagua]

Your Suntour stash is as big as mine! Very impressive.

But don't take your Ciocc apart -- I can't use a pulley bolt unless I can extend the threads up its full length and somehow modify the head. I have a pair of GPX derailleurs to pull spares from, but the countersink head is the magic ingredient for this mad quest I'm on.

I guess I haven't quite illustrated this: instead of going through the inside cage plate, the pulley, and the outer plate, I want to go through *only* the outer plate -- I'm trying to use a different cage that mounts to the pivot through a hole separate from the pulley-bolt holes. A wide-range GPX, you might say, is what I'm trying to create. If Suntour made it they'd call it the GPX-GT.

[oliver1850]

I can't quite envision what you're doing but I like the idea of a wide range GPX. Hope you will post a pic to further illustrate.

I'm running an XC Expert RD on a touring bike with GPX shifters. It will handle at least a 30 cog and looks good with the GPX parts.

http://www.ebay.com/itm/Vintage-Suntour-Maeda-XCE-Rear-Derailleur-Made-in-Japan-/272266477134?hash=item3f6458be4e:g:omkAAOSwt7pXLsF L