F & R Derailleur Limit Screws Anodised Blue

brady10

Happy New Year all;

Would anyone know where I could find blue limit screws for front and rear mech?

cheers
Josh

rockmonkeysc

Anodised would be aluminium and you really don't want aluminium stop screws.

poah

use some blue nail polish

rockmonkeysc

POAH wrote:

use some blue nail polish

What's your usual brand and shade?

Kowalski675

You could get blue titanium from Pro Bolt if you really must have them, but they aint cheap (and who's ever going to notice them anyway?). IMHO coloured fasteners should be left where they belong - in the 1990s...

rockmonkeysc

Ti isn't a particularly good material for very small screws. Fine for larger, low stress bolts.

Kowalski675

They're not under any load though, and won't wear as easily as ally, if he really must have blue. For me it would be inox all the way.

Chunkers1980

What? You mean like limit screws?

njee20

Alu will be absolutely fine in a mech. Not exactly high stress. I use ProBolt for alu bolts.

rockmonkeysc

They are tiny screws though likely to strip threads or heads.
Not sure you can get aluminium grub screws that small anyway.

CitizenLee

RockmonkeySC wrote:

They are tiny screws though likely to strip threads or heads.
Not sure you can get aluminium grub screws that small anyway.

You'd have to be pretty ham-fisted to strip the head or thread on a limit screw. Can't say I've ever seen it happen.

Kowalski675

RockmonkeySC wrote:

They are tiny screws though likely to strip threads or heads.

I thought your reasoning was more that their soft nature would mean the ends would get worn and your limits would go out of adjustment.

Not sure you can get aluminium grub screws that small anyway.

You can get 'em right down to M3x8.

Kowalski675

CitizenLee wrote:

RockmonkeySC wrote:

They are tiny screws though likely to strip threads or heads.
Not sure you can get aluminium grub screws that small anyway.

You'd have to be pretty ham-fisted to strip the head or thread on a limit screw. Can't say I've ever seen it happen.

Ally fasteners that small are very easy to round off heads in - doesn't take much torque at all. Wouldn't use 'em myself.

njee20

You can use nylon fasteners in stop screws if you want. They're doing sod all. It's not like you're going to be adjusting them constantly

rockmonkeysc

Nylon is surprisingly hard, I use it for wear parts on aggregate processing machines. It does absorb water and swell up though.

The Rookie

RockmonkeySC wrote:

Nylon is surprisingly hard, I use it for wear parts on aggregate processing machines. It does absorb water and swell up though.

Which is why you should put Nylon parts in a pan of boiling water for 5 minutes before use, it improves strength as well, and they won't later change dimension as they can't absorb any more water!

alexthebear

@ the OP I've just been onto the CRC website and amazingly there is no "mech limit screw" section so I'm affriad I can't help, sorry about that.

rockmonkeysc

The Rookie wrote:

RockmonkeySC wrote:

Nylon is surprisingly hard, I use it for wear parts on aggregate processing machines. It does absorb water and swell up though.

Which is why you should put Nylon parts in a pan of boiling water for 5 minutes before use, it improves strength as well, and they won't later change dimension as they can't absorb any more water!

Thats some bad engineering practice right there. It may not swell up any more but the dimensions will not remain consistent. Also you're altering the mechanical properties from known properties to unknown.

Chunkers1980

It's a plastic screw ffs. WGAF?

The Rookie

Incorrect post.....

The Rookie

RockmonkeySC wrote:

The Rookie wrote:

RockmonkeySC wrote:

Nylon is surprisingly hard, I use it for wear parts on aggregate processing machines. It does absorb water and swell up though.

Which is why you should put Nylon parts in a pan of boiling water for 5 minutes before use, it improves strength as well, and they won't later change dimension as they can't absorb any more water!

Thats some bad engineering practice right there. It may not swell up any more but the dimensions will not remain consistent. Also you're altering the mechanical properties from known properties to unknown.

Not at all, they will absorb the moisture eventually, so the key is to do it first, common practice for people who build RC race cars.

rockmonkeysc

It's not good practice. Possibly ok on RC cars but still bad practice. You're changing the materials properties from what the designer has based his calculations or FEA on to something unknown.

cooldad

FFS they're limit screws. Hardly safety critical parts.

The Rookie

RockmonkeySC wrote:

It's not good practice. Possibly ok on RC cars but still bad practice. You're changing the materials properties from what the designer has based his calculations or FEA on to something unknown.

You miss the point, they will change as the absorb moisture anyway, which will happen, by boiling you put them at their end state from the start, which is stronger and dimensionally they then don't change as they absorb moisture as they are already loaded.

It's better practice than starting with dimensionally unstable parts without the final strength the moisture brings.

As stated, not that relevant here apart from dimensionally for the limit screws.

rockmonkeysc

You say it's stonger but that can mean harder and more brittle. If you are using nylon in an application where its getting wet then you have got the wrong material. There are alternatives such as UHMWPE or PTFE which are more difficult to work and more expensive but more suitable.

The Rookie

They don't need to get wet, they absorb humidity from the air FGS, frankly you have no argument for not doing it, why not just admit you got it wrong!

Stronger, Young's modulus is higher and creep rates are reduced, that OK?

njee20

What is it with bolt threads (see what I did there!?) becoming arguments!? This has gone the way of the rotor bolt thread too.

The Rookie

Because engineers mention a point and lay people who don't actually know the answer argue the toss.....those that know don't then want to let the ignorant (in the true sense of the word) opinion be taken as the truth. If those that made the error held their hands up we could all move on.

rockmonkeysc

The Rookie wrote:

They don't need to get wet, they absorb humidity from the air FGS, frankly you have no argument for not doing it, why not just admit you got it wrong!

Stronger, Young's modulus is higher and creep rates are reduced, that OK?

You shouldn't be using it in a humid environment. Under normal conditions humidity isn't enough of an issue to worry about.
I prefer to design around KNOWN properties, not approximate values. I want to know exactly how a component will behave under load.

john2002

If they are standard m3 screw look on hobby rc shops.http://www.horizonhobby.co.uk/autoonline/j9trickbits/j9_hardware/j9_hardware.html
I think it's a bit pointless to bling up a derailleur screws.

njee20

Because engineers mention a point and lay people who don't actually know the answer argue the toss

Now I've had the bolt/screw argument before, and I've yet to hear a convincing argument aside from "I'm an engineer (which appear to be the answer to everything anyway), and I say so". That thread included. But anyway, no point revisiting that.

Can we start a thread for the 'engineers' to just have arguments? Few phrases are more irksome than "I'm an engineer", it would be good to contain 'em all in one place.