Removal of Seized Stroke Adjusting Screw of Rear Derailleur

[mtbvfr]

Hi Folks,

2 images attached.

I have a used Deore DX M560 Rear Derailleur with a Stroke Adjusting Screw that I haven't been able to unscrew any further because the head has become damaged due to the torque required to turn the screw. I am guessing that the screw and/or housing has some kind of corrosion that is making it difficult to turn.

I was lucky, I guess, that I was able to unscrew it enough to check the overall functionality on a bike with a 9-speed cassette.

I have managed to extract the Upper (small sprocket) screw but it was difficult too but I was able to fully grip the head with some pliers in order to do so.

With the Lower screw there is not enough head protruding in order to get sufficient grip. The edges of the heads are spherical (curve inwards towards the top of the head).

I did spray some WD-40 in there but still no go.

In order to not damage the body of the derailleur, what tools and techniques can I use to extract the screw?

When I get new screws, will Park Tool Anti-Seize Compound0 (ASC-1) be appropriate to prevent such problems in the future?

Thanks!!

 

[Uncle Grumpy]

Not a lot you can do other than use the widest flat blade screwdriver you can. Put downward pressure on it and turn slowly.

Bit too thin for an ezy-out to work.

Humouring the thread might help too - i.e. quarter turn and a bit out, quarter turn in, quarter and a bit out, quarter turn in etc. Might help the thread clean itself if there is anything causing it to bind. Work it back and forward, sounds counter intuitive when you want the damn thing out, but it does help.

Eventually you'll get it out enough for needle-nose pliers to get a grip.

If you're concerned about tools slipping then a couple of layers of masking tape on the silver aluminium won't hurt.

Remember, you're not beat until the screw head has sheared off.

On the new screw - any grease or anti-seize will help, as will blue Loctite which is a thread sealant more than a thread locker.

 

[hamster]

Hmm, nasty one. They have a very unusual head, for a Japanese standard cross head that is neither Phillips nor Pozi.
If the above fails (and it looks like you have already given it a good pickling in Plus-Gas) then you can try drilling down the middle backwards. The point is not to drill out the head, but the force moves the screw. Drill in a little, then set the drill backwards, a LHS bit is even better, although they tend to be some carbon tool steel not HSS and very brittle. A bit only sticking out 5mm or so is ideal so you can push REALLY hard.

 

[ishaw]

The black plastic bit might come out. Can't remember it's been a long while since I had a dx mech. Might give more room for pliers perhaps?

You could try unscrewing from the rear, if you can reach the threaded part, use long nose pliers to turn it until you can grip the head end again.

 

[dan28]

if the screw is neither philips or pozi it will be JIS have a look at us pro jis screwdriver set

 

[bikeworkshop]

The plastic only comes out only once the screws are removed - however it might be worth sacrificing to expose enough head to get some longnose moleys on there.