I just tried threading a rear deraileur on my new frames hanger and either I messed up the threads by forcing it a little or they were already messed up.Assuming its the hanger threads and not the derailleur how can I fix it.Are the hangers universally threaded for both Italian and japanese parts?The frame is Pinarello and the derailleur was shimano.

Yes it should be the same standard for any derailleur made today.
You could try threading the derailleur bolt (or another derailleur bolt removed from a broken derailleur you have laying around) in from the back - this can sometimes be done to partially clean up the pedal threads on partially cross-threaded crankarms. You could also get the right tap and clean out the threads that way. Or you could buy a new derailleur hanger (assuming it is a replaceable derailleur hanger).

The easiest thing to try first is to CAREFULLY insert a lubricated bolt from the opposite side of the hole and use it to chase the deformed threads back into shape. DO NOT FORCE IT. Since it is a new frame it is possible that the threads are clogged with paint. If so you may need to run a tap through the holes to clean them out. In a pinch you might be able to file some threads off of a bolt to fashion it into a crude tap, although using the correct tool is always the best course.

It the threads are truly trashed the hole can be drilled oversized and tapped using a special tap for a Helicoil insert. This will make new threads which are stronger than the original. If it is a replaceable hanger then that is the last resort option. If you do buy another pick up a spare, it may save your bacon down the road.

EDIT: Lardasse beat me to it while I was typing!

Derailleur hangars are threaded M10x1.0 mm which is not a common hardware store size so you will have to use an old derailleur or a rear hub axle (most use the same thread) to clean out the hanger threads. Your LBS will have the proper tap and can do the job in a minute unless the threads have really been destroyed.

After that there are three options: 1) A new (replacable) hanger iif the frame uses one or 2) a "dropout saver" which is a bushing that replaces the old threads after the original hole is drilled oversize or3) a helicoil insert.

If your frame is worth more than $11.00 and the thread is just needs reforming, get one of these to make the job easier. As per above posts, if the thread is beyond repair there are workarounds.

Campagnolo derailleurs and hangers used a 10x26tpi thread until roughly 10 years ago. That can make a Shimano 10x1 derailleur bolt get a bit tight about half way in. Folks have been cheating these is forever, so it won't be a problem unless you make a habit of switching back and forth between 10x1 and 10x26 bolts.

I have a nother Pinarello Montello and the dropouts are marked "Campagnolo"This Montell the dropouts are marked"Pinarello"Could they be different size?I put a Shimano 600 on the other with no problems.

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As I said, Campagnolo changed from their classic 10x26 thread to 10x1 a bit over 10 years ago. If you have vertical dropouts they're most likely 10x1. In any case it doesn't really matter. The thread depth is only 7-8 threads and they can deform to accommodate the very slight (25.4 vs 26tpi) difference in pitch.

I've only seen it become an issue when going back and forth, or retapping to the other thread, where some flaking or shaving of the threads happens, but even then it takes quite a bit of abuse to actually strip it. Worst comes to worst, you can always fit a 0x1 helicoil insert and be good for another half century.

Depending upon how much material there is around the derailleur-hanger hole in the dropout, you can use an insert to replace the damaged threads:



If the mounting bolt on the derailleur is long enough, like sticks out the back side by 2mm, I've been able to put a thin nut around it. The tiny thin 10x1mm locknuts used for holding lightbulb sockets onto lamps works well. In the picture below, it's the thin hex-nut right above the knurled ring:


https://www.homedepot.com/catalog/pro...552a7f_300.jpg

Depending upon how much material there is around the derailleur-hanger hole in the dropout, you can use an insert to replace the damaged threads:



If the mounting bolt on the derailleur is long enough, like sticks out the back side by 2mm, I've been able to put a thin nut around it. The tiny thin 10x1mm locknuts used for holding lightbulb sockets onto lamps works well. In the picture below, it's the thin hex-nut right above the knurled ring:


https://www.homedepot.com/catalog/pro...552a7f_300.jpg

Happy to report i succeeded to thread the derailleur onto the hanger!I first checked the derailleur on another bike and it went on smooth as sugar.So when I tried it again I used a little more pressure where it binded at, bypassing that, and it snuggly extended to the end.Thanks All!