Quick Q. re screw heads eg derailleur mech stop screws...

[Bmblbzzz]

I too, and I expect a few hundred others, would love to know more about replacing JIS mech screws with allen screws.

[Paulatic]

Are they M4?

https://boltbase.com/a2-stainless-steel ... screws-p33

[AndyK]

Are they M4?

https://boltbase.com/a2-stainless-steel ... screws-p33

I just had a look at the "exploded view" parts diagrams for half a dozen different Shimano rear mechs - road and offroad, various ages - and the limit adjuster screws for all of them were listed as being M4. So I'm guessing it's a yes. The length of the screws varied widely, though, from 11.5mm to 20mm. On some, the lower-limit screw was a different length from the upper-limit screw. I guess it wouldn't matter if you fitted a replacement that was a bit too long, but there might be models where an excessively-long one would get in the way of the mechanism.

The most recent high-end Shimano road rear mechs (Ultegra/Dura-Ace/105) come with allen bolts for the limit and b-screw adjusters already fitted - in fact they're designed so you can install and adjust a new mech using only only a set of allen keys.

[keyboardmonkey]

The issue of JIS or JIS-compatible screwdrivers has popped up on here several times over the years. If you’re not looking to go down the hex key fastener route my bottom line is to get a Vessel Megadora 900 +2 for the likes of Shimano derailleur limit screws and the +1 for tiny fasteners typically found on brake lever covers. (The + symbol indicates a cross head; the - symbol a slotted head.)

Having said that, many modern screwdrivers meet the discontinued JIS standard. Look for DIN 5260-PH/ISO 8763.

From a useful web site:

“Note, for the tool standards geeks: While I use the term "JIS-compatible screwdriver," these days there is no such thing as a "JIS screwdriver" as Japanese Industrial Standards no longer have a screwdriver spec, and DIN 5260-PH/ISO 8763-1 has taken its place as the screwdriver standard to use with JIS screws…”

Further reading:

https://bikex.org/learn/tech-tips/jis-s ... rewdrivers

[Airsporter1st]

Do people who do this many times a day deliberately buy JIS screwdrivers? Or do they find a specific screwdriver that works well in practice whatever it's labelled?

Thanks

Jonathan

There is only one specific screwdriver for JIS heads and that is a JIS one. Other profiles will fit, but just as using Philips in a Posidrive and vice versa, there is a risk of damaging the screwheads/ driver.

Given relatively low cost and reasonable availability, I would suggest its generally better to obtain the correct driver.

[Brucey]

Are they M4?.....

normally, yes, although old sun tour mechs were different; they used a weird fine pitch thread.

If you examine these screws very carefully, you will probably find that they have relieved (ie. threadless) tips, in which the tip of the screw is of slightly smaller diameter and devoid of threads. This is to ensure that if a burr develops on the tip of the screw (as is often the case with 'B' screws and 'L' screws) the burr cannot foul the female thread. Since this feature is not difficult to replicate (eg. via SG) it seems positively churlish to use standard (ie. unmodified) screws.

The JIS headed screws fitted to RDs often have a slot for a flat blade as well; if you don't have the correct screwdriver, you can use this instead, even if you have to grind a screwdriver so that it fits properly.

[simonineaston]

There is only one specific screwdriver for JIS heads and that is a JIS one. Other profiles will fit, but just as using Philips in a Posidrive and vice versa, there is a risk of damaging the screw heads/ driver.

Back when I had bikes equipped with Disraeli gears, I used to use the sort of electricians screwdriver that were common back then, with its slightly worn and rounded blade. This always seemed a good fit in stop screw heads. Still got it

photo of old screw driver

IMG_1113.jpeg (7.13 KiB) Viewed 2220 times

EDIT

often have a slot for a flat blade as well...

It's that slot that has always confused me. So that's the bottom line, is it?! Those bolts are JIS but adapted to let us flat blade screwdriver owning plebs adjust our Disraeli gears, too! How thoughtful!

[rjb]

Is that screwdriver the sort that lights up when you plug it into the mains and then complete the circuit by placing your licked finger on the stud at the top. Never felt comfortable using one. Can you still buy them or has elf & safety caught up.

[Jdsk]

Still widely available:
https://www.amazon.co.uk/s?k=neon+screw ... nb_sb_noss

Jonathan

[irc]

There are JIS screwdriver sets by Sealey on Ebay for £16, Why not have the right tool? Or half that for a brand I don't recognise.

[keyboardmonkey]

There are JIS screwdriver sets by Sealey on Ebay for £16, Why not have the right tool? Or half that for a brand I don't recognise.

Nothing against Sealey - I’ve got some of their stuff - but this is as close as you get to an industry standard (mine was about £6 when I got it eight years ago)…

Vessel Megadora 900 +2 screwdriver

IMG_2320.jpeg (93.44 KiB) Viewed 2142 times

Vessel Megadora 900 +2 screwdriver on Amazon:

https://www.amazon.co.uk/Vessel-Megador ... rewdriver/

[Brucey]

this one?

https://www.amazon.co.uk/Vessel-900-Meg ... 00bb6&th=1

seems to have gone up by all of 50p.....

p.s. sorry, but my brain scrambled that into '£8 six years ago'.

[keyboardmonkey]

this one?

https://www.amazon.co.uk/Vessel-900-Meg ... 00bb6&th=1

seems to have gone up by all of 50p.....

Turns out I actually placed this order, which will have been the best price at the time. I do think it’s worth having the +1 screwdriver as well…

Amazon order - 2017

[axel_knutt]

Do people who do this many times a day deliberately buy JIS screwdrivers? Or do they find a specific screwdriver that works well in practice whatever it's labelled?

Thanks

Jonathan

A few years ago my trusty Pozidriv of forty years broke before the Loctite on a pedal screw did, so I did the rounds of the DIY sheds, but couldn't find a single screwdriver anywhere that didn't have a magnetic tip. Just as I was about to give up hope, I thought I'd pop in the LBS as I was passing and ask if they sold them:

"What's a Pozidriv?"
I explained.
"A Phillips you mean?"
I explained the difference.
"Huh, they're all crossheads to me mate"

[Bmblbzzz]

Well, he was right; they all are crosshead varieties! And if, as might well be the case, 95% of the ones you deal with are the same type, then it doesn't really matter whether you give them the "correct" name, as long as the variety of screwdriver you have is the right sort.