Broken Derailleur Tab

(Arthur Shapiro) said:

I'm sure this is a routine issue to people who work with metal. It isn't routine to me. Can anyone
discuss the proper method for ensuring that a hole is truly centered at the intended location? Is
there perhaps a particular sort of punch that is intended to address this situation?

Art

There are 'self-centering' punches. Basically a face that fits into a countersunk hole with a center
pin that can be punched to make a center mark once the tool is aligned. An example:

tools.aubuchonhardware.comself centering punches 304405.aspOpen ↗

Not the best way to achieve aligned holes in any material, but it should work well enough for
attaching the hanger.

use a drill press too...or have the shop do it.

"Arthur Shapiro" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Yesterday, for the third time, the derailleur tab fractured on my Klein Quantum.

I absolutely detest the bicycle (long story available via Google) but use

it

Quoted message said:

sporadically for my short commute. I had intended to put the headlights taillights on this week in
preparation for the time change on Sunday, whereupon I'd use it more faithfully for commuting, not
wanting to put

that

Quoted message said:

stuff on the good bike.

I dragged it over to the local pro LBS, and they determined that an aftermarket Santana stainless
steel hanger would fit beautifully, and doubtlessly be stronger than the flimsy Klein's tab. So I
purchased it.

The replacement mounts to the existing rear dropout by three small metal screws, meaning that the
dropout has to be drilled and tapped. I'm

absolutely

Quoted message said:

terrified of this, and am seeking advice. I know that when doing the same thing in wood, for
example for mounting hinges, one can centerpunch the

holes,

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using the hinge as its own template, and then drill the screw holes. Even then, it's almost
impossible to get the punch mark dead center in the

hole,

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meaning that inevitably one or more of the screws either barely fit or

simply

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don't fit. With something metal, there's no opportunity to fix and redo a slightly offset hole,
and slightly offset doubtlessly won't be good

enough.

Quoted message said:

These three holes have to be drilled in precisely the right place, with

very

Quoted message said:

little leeway.

I'm sure this is a routine issue to people who work with metal. It isn't routine to me. Can anyone
discuss the proper method for ensuring that a

hole

Quoted message said:

is truly centered at the intended location? Is there perhaps a particular sort of punch that is
intended to address this situation?

Art

I recommend drilling/tapping the first hole, then mounting the hanger. From there you could use a
bit about the same diameter as the holes in the hanger for the subsequent mounting holes, drilling
just enough to create a conic depression in the dropout. Finally, use the correct drill bit to
finish things off.

"Arthur Shapiro" <[email hidden]> wrote in message
"]news:[email hidden]...

snippage

Quoted message said:

The replacement mounts to the existing rear dropout by three small metal screws, meaning that the
dropout has to be drilled and tapped. I'm

absolutely

Quoted message said:

terrified of this, and am seeking advice. I know that when doing the same thing in wood, for
example for mounting hinges, one can centerpunch the

holes,

Quoted message said:

using the hinge as its own template, and then drill the screw holes. Even then, it's almost
impossible to get the punch mark dead center in the

hole,

Quoted message said:

meaning that inevitably one or more of the screws either barely fit or

simply

Quoted message said:

don't fit. With something metal, there's no opportunity to fix and redo a slightly offset hole,
and slightly offset doubtlessly won't be good

enough.

Quoted message said:

These three holes have to be drilled in precisely the right place, with

very

Quoted message said:

little leeway.

[email hidden] (Arthur Shapiro) wrote:

[snip]

Quoted message said:

These three holes have to be drilled in precisely the right place, with very little leeway.

I'm sure this is a routine issue to people who work with metal. It isn't routine to me. Can anyone
discuss the proper method for ensuring that a hole is truly centered at the intended location? Is
there perhaps a particular sort of punch that is intended to address this situation?

Yes, it's called a transfer punch. Here's a picture:
<http://www.cleavelandtool.com/catalog/WEBtps7.JPG>

Borrow one that's a close fit in the hole in the derailleur mount. Give it a *light* tap, just to
mark the location, then use a regular centerpunch to make a deeper centering mark. (I once got
chewed out by a machinist for using a borrowed transfer punch as a centerpunch.)

As someone else suggested, drill and tap one of the holes, then mount the bracket by one screw so
you can make sure the other holes line up.

Or you could have the LBS attach the thing.

--
Ray Heindl (remove the X to reply)

The flimsy derailer hanger is there to protect the aluminum dropout from bending and messing
the frame.

If you install a steel hanger the next time you wack the derailer you may be in the market for a new
frame instead of a crummy aluminum derailer hanger.

Marcus

In article said:

If you install a steel hanger the next time you wack the derailer you may be in the market for a
new frame instead of a crummy aluminum derailer hanger.

Marcus, I think you don't understand: the tab IS (or WAS) part of the frame. it wasn't some
detachable sacrificial entity. In other words, I've trashed the frame unless I do something
significant.

Art

Art Temporary usercode - to be deleted when spam starts. Use MyBrainHurts at this ISP to reach me

In article said:

Yes, it's called a transfer punch. Here's a picture:
<http://www.cleavelandtool.com/catalog/WEBtps7.JPG>

Thanks to you and the other resondents...that makes a lot of sense.

A further question: how do I measure the threading in order to purchase the correct tap? My tap
collection is minimal, and primarily American, whereas these screws seem to take a 2mm metric Allen
wrench. What do I go out and purchase, and how do I determine the correct corresponding drill bit? I
don't have anything along the lines of a "machinist's handbook" in the shop.

Art

Art Temporary usercode - to be deleted when spam starts. Use MyBrainHurts at this ISP to reach me

Arthur Shapiro said:

In article said:

If you install a steel hanger the next time you wack the derailer you may be in the market for a
new frame instead of a crummy aluminum derailer hanger.

Marcus, I think you don't understand: the tab IS (or WAS) part of the frame. it wasn't some
detachable sacrificial entity. In other words, I've trashed the frame unless I do something
significant.

Art

Art,

Your approach makes a whole lot more sense now. I thought it was one of those replaceable hangers
that you had become fed up with and were looking for a beefier one. Thanks for the enlightenment.

Marcus

(Arthur Shapiro) said:

A further question: how do I measure the threading in order to purchase the

Bring screw into Home Depot. Go to hardware aisle. Try it on different nuts until you find your
Cinderella.

Or just buy/borrow a thread-measurer and a vernier/dial caliper.

Quoted message said:

correct tap? My tap collection is minimal, and primarily American, whereas these screws seem to
take a 2mm metric Allen wrench. What do I go out and purchase, and how do I determine the
correct corresponding drill bit? I don't have anything along the lines of a "machinist's
handbook" in the shop.

The info is easy to find online. Google for words like tap drill size chart

engineersedge.comtap drill chart.htmOpen ↗ engineersedge.comDesign Data.shtmlOpen ↗
carbidedepot.comformulas tap standard.htmOpen ↗ carbidedepot.comresources.aspOpen ↗

Chalo, IIRC, is a machinist and probably knows incredibly easy ways to deal with all this stuff
(better than anything I can suggest) but seems to be not reading this thread.
--
Rick Onanian

Quoted message said:

In article said:

If you install a steel hanger the next time you wack the derailer you may be in the market for a
new frame instead of a crummy aluminum derailer hanger.

Arthur Shapiro said:

Marcus, I think you don't understand: the tab IS (or WAS) part of the frame. it wasn't some
detachable sacrificial entity. In other words, I've trashed the frame unless I do something
significant.

like this? yellowjersey.orgrlfix.htmlOpen ↗

--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

Arthur Shapiro said:

A further question: how do I measure the threading in order to purchase the correct tap? My tap
collection is minimal, and primarily American, whereas these screws seem to take a 2mm metric
Allen wrench. What do I go out and purchase, and how do I determine the correct corresponding
drill bit? I don't have anything along the lines of a "machinist's handbook" in the shop.

With a 2mm allen head it's probably: 3mm x 0.5, tap drill 2.5mm. Use a #39

Other common metric fasteners used there: 4mm x 0.7, tap drill 3.3mm. Use a #30 5mm x 0.8, tap drill
4.2mm. Use a #19

--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

Arthur Shapiro said:

Marcus, I think you don't understand: the tab IS (or WAS) part of the frame. it wasn't some
detachable sacrificial entity. In other words, I've trashed the frame unless I do something
significant.

and

Quoted message said:

I absolutely detest the bicycle (long story available via Google) but use it sporadically for my
short commute.

I have an elegant mechanical solution.

1. Take frame to shop

2. Tell underpaid but deserving shop-rat "I'll trade you this here Klein frame for a nice older
Specialized or Miyata touring frame in good condition that fits and will be good for my lights
and other commuting stuff"

3. Let shop-rat figure out how to mount derailleur hanger

All problems taken care of! The der hanger is a solvable problem, the fact that you detest the
bike is not.

"Rick Onanian" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

(Arthur Shapiro) said:

A further question: how do I measure the threading in order to purchase the

Bring screw into Home Depot. Go to hardware aisle. Try it on different nuts until you find your
Cinderella.

Or just buy/borrow a thread-measurer and a vernier/dial caliper.

I remember a couple of times, when I was a poor engineering student, locating an open tap & die set
at a Sears store, then doing a quick job right there in the aisle.

In article said:

like this? yellowjersey.orgrlfix.htmlOpen ↗

Yep, except that gentleman specifically doesn't want to deal with aluminum.

I appreciate everyone's input, and have a pretty good feel for what's needed now. BTW, the shop guru
(and he's good) mentioned that he once put on one of the replacement hangers with JB Weld, and no
screws, and it has held for several years for the customer. He notes that there's plenty of clamping
pressure from the QR skewer, anyway.

Art Temporary usercode - to be deleted when spam starts. Use MyBrainHurts at this ISP to reach me

(Arthur Shapiro) said:

Yesterday, for the third time, the derailleur tab fractured on my Klein Quantum.

Rats.

Quoted message said:

The replacement mounts to the existing rear dropout by three small metal screws, meaning that the
dropout has to be drilled and tapped. I'm absolutely terrified of this, and am seeking advice.

...

Quoted message said:

With something metal, there's no opportunity to fix and redo a slightly offset hole, and slightly
offset doubtlessly won't be good enough. These three holes have to be drilled in precisely the
right place, with very little leeway.

I see that someone has already suggested a transfer punch. This will work.

Since the frame has no holes tapped in it yet, you are not wedded to a particular screw size. Any
screw that fits through the adapter's holes will do, if that makes it easier to find a tap. In this
case, you should err on the side of a larger fastener, because little taps are easy to break and
hard to remove.

If the screws are outside the area covered by the axle locknut, there is another option. You can pop
rivet the hanger on. That would even allow you to use the hanger as a drill template, since the
holes in the hanger and in the frame would be the same size.

Rivets are strong, reliable, easy to set, easy to remove, and they circumvent the need to tap your
frame. A 3mm screw would be substituted by a 1/8" rivet; a 4mm screw by a 5/32" rivet.

Chalo

(Chalo) said:

you should err on the side of a larger fastener, because little taps are easy to break and hard
to remove.

You can say that again. Any links to tips on removing broken taps? I have the remnant of a small tap
living in a mounting-screw hole in an electric motor for an air compressor. I settled for mounting
it with three screws.

Quoted message said:

is another option. You can pop rivet the hanger on. That would even

Rivets are strong, reliable, easy to set, easy to remove, and they circumvent the need to tap your
frame. A 3mm screw would be substituted by a 1/8" rivet; a 4mm screw by a 5/32" rivet.

Are these rivets different than the standard (for their application, anyway) rivets found in
aluminum gutters and downspouts? These are
1/8", and I can't imagine them being useful for any bicycle application, as they are pretty easy to
break. FWIW, they are most likely aluminum, and you are most likely talking about steel (right?).

Quoted message said:

Chalo

--
Rick Onanian

Rick Onanian <[email hidden]> wrote::

Quoted message said:

Any links to tips on removing broken taps? I have the remnant of a small tap living in a
mounting-screw hole in an electric motor for an air compressor.

Take it to a machine shop that has a disintegrator.

Quoted message said:

Quoted message said:

You can pop rivet the hanger on.

Rivets are strong, reliable, easy to set, easy to remove, and they circumvent the need to tap
your frame. A 3mm screw would be substituted by a 1/8" rivet; a 4mm screw by a 5/32" rivet.

Are these rivets different than the standard (for their application, anyway) rivets found in
aluminum gutters and downspouts? These are
1/8", and I can't imagine them being useful for any bicycle application, as they are pretty easy
to break. FWIW, they are most likely aluminum, and you are most likely talking about steel
(right?).

Pop rivets are available in aluminum and steel, in 3/32", 1/8", 5/32", and 3/16" sizes. Their
clamping tension depends a lot on the structural integrity of the pieces being clamped, and on the
fit of the rivet to the drilled hole. If steel rivets are used, they should be plenty strong enough
for the purposes.

Chalo Colina

(Chalo) said:

Rick Onanian <[email hidden]> wrote::

Quoted message said:

Any links to tips on removing broken taps? I have the remnant of a small tap living in a
mounting-screw hole in an electric motor for an air compressor.

Take it to a machine shop that has a disintegrator.

Knowing that something called a "disintegrator" actually exists, I would damn near go to a machine
shop just to see one. So cool!

Quoted message said:

Quoted message said:

application, as they are pretty easy to break. FWIW, they are most

and 3/16" sizes. Their clamping tension depends a lot on the

I was more concerned with the rivets themselves breaking, the mushroomed end breaking off at the
transition to the shaft.

Quoted message said:

the rivet to the drilled hole. If steel rivets are used, they should be plenty strong enough for
the purposes.

That answers that question. 🙂

Quoted message said:

Chalo Colina

--
Rick Onanian

[email hidden] (Chalo) wrote in message
news:<[email hidden]>...

Quoted message said:

Rick Onanian <[email hidden]> wrote::

Quoted message said:

Any links to tips on removing broken taps? I have the remnant of a small tap living in a
mounting-screw hole in an electric motor for an air compressor.

Take it to a machine shop that has a disintegrator.

[snip]

Dear Chalo,

Is this disintegrator what Phil Brown had in mind in last months "Broken Screw Extraction: 4 mm?"
thread when he suggested that Pete Cresswell should:

Find out who your local kotorcycle shop uses for this sort of thing. There is a process whose name
escapes me using electrical current to remove the broken screw.

If so, is there a short explanation of how it works? Cathode or anode deposition or something
like that?

Carl Fogel