Brakes: changing from nutted to recessed?

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...

> > Do you _have_ an example of a cut-thread cycle brake bolt that failed?
> >
> > That's the issue.
>
> no it's not - it's about the op's dental bills.
>

If the bolt won't break there'l be no dental bills.

Cut versus rolled threads won't make the bolt break - it's strong enough
even with cut threads. That's why you can see both types on threads on
brake bolts - and QR skewers, for that matter.

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> >>To do rolled threads, you would need to start with a skinnier rod,
> >>instead of the standard 6 mm diameter.
> >>
> >>Sheldon "Misinterpreted" Brown
> >
> >
> >
> > Fair enough.
> >
> > Ed Chait
> >
> >
> no it's not fair enough. it's real simple to achieve a 6mm shaft with a
> 6mm rolled thread - you have a shouldered shaft, part 6mm and part
> 5.5mm, /then/ you roll the thread into the 5.5mm section. it amazes me
> that this is not obvious.

Oh come off it, we all know how rolled threads are made.

Telling us how they are made will not convice us that cut threads on a brake
bolt are a disaster waiting to happen - neither will providing mis-leading
examples of bolts that break for other reasons.

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...

> >
> > To do rolled threads, you would need to start with a skinnier rod,
> > instead of the standard 6 mm diameter.
>
> not correct - the rod has two sections of two different diameters - the
> threads are rolled onto the skinnier section whose diameter is specially
> chosen to match the "rise" of the rolled threads leaving the two
> sections of nominally the same diameter. you'd believe it if you saw
> either a sectioned bolt or an unthreaded blank. the brake bolt is one
> example, the qr skewer rod is another.

Not all skewers have rolled threads - and why do you think telling us what
we know already (how rolled threads are made) will convince us that cut
threads are dangerous when used on brake-bolts?

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> >
> > If you would have read the text on that page, instead of just looking at
> > the pictures, you'd understand that this brake was used with the
> > mounting bolt loose, which put a significant bending stress on the bolt.
> >
> > When the bolt is properly tightened, the stress is mainly tension, for
> > which it is designed.
>
> i understand all that: the point is that a cut thread can have the same
> result because it's not as fatigue resistant!
>

Any bolt will break, given enough of a load. This breaking load will, of
course, be different for different types of stress. In the special case of
fatigue, yes, a bolt with cut threads will have a lower breaking stress -
and likely for a bending load as well.

But that is not (no matter how loudly and variously jim beam attempts to
distract) the issue.

The strength of a cut-thread brake-bolt _is_ sufficient to handle normal
loads. Now obviously, an Alarmist (and/or Idiot) can come up with a way
that a cut-thread bolt will fail, either on usenet or in real life, but
non-Idiots neither allow their brake-bolts to be so loose that bending
stress occurs, nor worry whether the manufacturer has chosen to make the
bolt with cut or rolled threads.

 

[jtaylor]

"Phil, Squid-in-Training" <[email protected]> wrote in
message news:[email protected]...
>
> I agree, but I think what is a good thing to explain at this point is the
> fatigue difference between rolled threads and cut threads. Numbers,
please.
> Failure modes, please. Reasons, data, everything!
>

The numbers vary, but the difference in strength is usually quoted as around
30-40%.

So in a situation where the loads vary widely (as they do in cycle brakes;
you can have a little old lady weighing 100 lbs doing 10 mph on the way to
the post office, or over 400 lbs of riders and gear on a tandem going
downhill at five times that speed), and you'd expect that if the brake bolt
has a margin of extra strength only 30-40%, well, then, some would break,
rolled or cut.

A perfect example exists in the cycle world - spokes.

We all know spokes have rolled threads, for exactly the reason that jim beam
is suggesting is necessary for brake bolts and qr skewers; and yet, spoke
failures are common. There are some people who can build wheels well enough
that they can get spokes to last through many rims, but there are many
wheels built poorly enough that the extra strength of rolled threads is not
enough to prevent them breaking.

So we have one situation where rolled threads are universally used and yet
there are many, many failures; so many that cycle makers have even seen fit
to make braze-ons to hold replacement spokes. Most of us have had broken
spokes, I would wager - but how many of us have seen or heard of a broken
brake-bolt? I should remind readers that the jim beam example does not
qualify, as that failure was due to the brake bolt being so loose that the
bolt failed from bending stress.

Surely if rolled threads were a necessity for brake bolts it would be known
because some of them would break under extreme conditions. A cut-thread
bolt (or QR skewer) is, all else being equal, weaker, that is not in
dispute; but cut threads are used all the time in situations where the extra
strength is not required. The threads on vice screws, for instance.

Rolled threads will also be found in situations where they are _not_
required - the case screws on your computer are most probably formed rather
than cut; but that does not mean the manufacturer has decided that the extra
strength is worth pursuing; more probably that it is cheaper to do so.
Alarmists may look at these bolts and, knowing a smattering of technology
and jargon, decide that since they are rolled, it must be so because the
extra strength is needed; they should instead look to see if in the real
world there are failures.

 

[Ted Bennett]

In article <[email protected]!nnrp1.uunet.ca>,
"jtaylor" <[email protected]> wrote:

> "Phil, Squid-in-Training" <[email protected]> wrote in
> message news:[email protected]...
> >
> > I agree, but I think what is a good thing to explain at this point is the
> > fatigue difference between rolled threads and cut threads. Numbers,
> please.
> > Failure modes, please. Reasons, data, everything!
> >
>
> The numbers vary, but the difference in strength is usually quoted as around
> 30-40%.
>
> So in a situation where the loads vary widely (as they do in cycle brakes;
> you can have a little old lady weighing 100 lbs doing 10 mph on the way to
> the post office, or over 400 lbs of riders and gear on a tandem going
> downhill at five times that speed), and you'd expect that if the brake bolt
> has a margin of extra strength only 30-40%, well, then, some would break,
> rolled or cut.
>
> A perfect example exists in the cycle world - spokes.
>
> We all know spokes have rolled threads, for exactly the reason that jim beam
> is suggesting is necessary for brake bolts and qr skewers; and yet, spoke
> failures are common. There are some people who can build wheels well enough
> that they can get spokes to last through many rims, but there are many
> wheels built poorly enough that the extra strength of rolled threads is not
> enough to prevent them breaking.
>
> So we have one situation where rolled threads are universally used and yet
> there are many, many failures; so many that cycle makers have even seen fit
> to make braze-ons to hold replacement spokes. Most of us have had broken
> spokes, I would wager - but how many of us have seen or heard of a broken
> brake-bolt? I should remind readers that the jim beam example does not
> qualify, as that failure was due to the brake bolt being so loose that the
> bolt failed from bending stress.
>
> Surely if rolled threads were a necessity for brake bolts it would be known
> because some of them would break under extreme conditions. A cut-thread
> bolt (or QR skewer) is, all else being equal, weaker, that is not in
> dispute; but cut threads are used all the time in situations where the extra
> strength is not required. The threads on vice screws, for instance.
>
> Rolled threads will also be found in situations where they are _not_
> required - the case screws on your computer are most probably formed rather
> than cut; but that does not mean the manufacturer has decided that the extra
> strength is worth pursuing; more probably that it is cheaper to do so.
> Alarmists may look at these bolts and, knowing a smattering of technology
> and jargon, decide that since they are rolled, it must be so because the
> extra strength is needed; they should instead look to see if in the real
> world there are failures.

Your comments may be valid for brake bolts but not for spokes, which do
not fail at the threads, typically. Spokes break as a result of fatigue
of the spoke at the elbow, and I'm surprised that you are not aware of
that.

Ted

--
Ted Bennett

 

[Frank Krygowski]

Ted Bennett wrote:
> In article <[email protected]!nnrp1.uunet.ca>,
> "jtaylor" <[email protected]> wrote:
>
>>
>>A perfect example exists in the cycle world - spokes.
....
>
> Your comments may be valid for brake bolts but not for spokes, which do
> not fail at the threads, typically. Spokes break as a result of fatigue
> of the spoke at the elbow, and I'm surprised that you are not aware of
> that.

FWIW, I've broken nearly as many spokes at the threads as at the elbows.
(Although I don't break many spokes at all.)

I don't know why I've seen so many thread failures. Perhaps the rims
I'm using on those bikes (old Weinmann A-129) don't align the spokes
toward the hub very well.

- Frank Krygowski

 

[Michael Press]

In article
<h%[email protected]>,
Frank Krygowski <[email protected]> wrote:

> Ted Bennett wrote:
> > In article <[email protected]!nnrp1.uunet.ca>,
> > "jtaylor" <[email protected]> wrote:
> >
> >>
> >>A perfect example exists in the cycle world - spokes.
> ...
> >
> > Your comments may be valid for brake bolts but not for spokes, which do
> > not fail at the threads, typically. Spokes break as a result of fatigue
> > of the spoke at the elbow, and I'm surprised that you are not aware of
> > that.
>
> FWIW, I've broken nearly as many spokes at the threads as at the elbows.
> (Although I don't break many spokes at all.)
>
> I don't know why I've seen so many thread failures. Perhaps the rims
> I'm using on those bikes (old Weinmann A-129) don't align the spokes
> toward the hub very well.

Yes, probably mis-alignment induced strain cycling near
the nipple. Stress relieving the tensioned wheel at build
time usually plastically deforms the spoke near the nipple
and prevents this source of spoke failure. There is
another procedure: after lacing the wheel, individually
bend each spoke near the nipple to provide a fair lead
from hub to rim spoke hole.

--
Michael Press

 

[[email protected]]

jim beam wrote:
[edited]
> >>oh dear. sorry to burst your bubble, but i've yet to see a single
> >>brake pivot bolt that's not rolled. /you/ may be able to imagine
> >>one, or even make one just for spite, but no competent manufacturer
> >>[or engineer] is going to use one in something they sell and for
> >>which they have legal liability. kinda takes the steam out of the
> >>"both would break" argument if only one kind is sold.

> numbers are not something easily calculated. the quickest, easiest way
> is to test. that said, there are numerical factors that contribute like
> thread root radius, notch sensitivity of the material, etc.
>
> regarding more qualitative factors that differentiate, these include
> dislocation density, inclusion count, residual stress, die scarring,
> microstructure, etc.

You were pretty sure earlier. Now you're saying there
are lots of factors and the numbers aren't easily calculated.
This may be true, but it also sounds like you don't have a
calculation or test result that backs up the earlier claim.

> >>>a) find threads of both types on brake bolts
> >>
> >>go ahead and show one. post some pics.

Elsewhere in this thread I gave two examples of brake
bolts I'd found that appeared cut, not rolled. These
were an old Shimano original 105 and a Suntour Superbe
drop-bolt. If you can wait until Monday or Tuesday, I
will post pictures, within the limited macro ability of
my digicam. For starters, I can say that these bolts
definitely did not start off thick and get necked down
to the threaded part, as current Shimanos do.

 

[A Muzi]

> "philcycles" <[email protected]> wrote in message
> news:[email protected]...
>>Just as an aside, I'll bet the mounting bolt is chromed. Trying to cut
>>threads on a chrome bolt wil ruin the die in short order.

jtaylor wrote:
> Well, it depends on what you mean by "short", the type of dieand the kind of
> chromium plating.
> The typical case would be running a die an extra 20mm along a flash-chrome
> plated bolt; even a cheap carbon-steel fixed-diameter die will probably do
> that <some multiple of 10> times without trouble.

We break chrome with emery before using a die or other
cutting tool

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

 

[A Muzi]

-snip brake bolts-
> jtaylor wrote:
>> Do you _have_ an example of a cut-thread cycle brake bolt that failed?
>> That's the issue.

jim beam wrote:
> no it's not - it's about the op's dental bills.

The comment from one contributor about still riding with a
Ballila brake (fearless!) pretty much establishes that the
dimensions of a 6mm steel brake bolt are plenty large to
secure a brake to a bicycle. Since we've established that
all the classic equipment is cut thread and that even the
worst of those can give 40 years of service, don't you agree
that any differences are just lost in the noise? Sure rolled
threads are a better way to go , it's just overkill in this
application.

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

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...

> numbers are not something easily calculated. the quickest, easiest way
> is to test.

Wouldn't the best test be what happens in the real situation?

Say we have, oh, 100 million cycles out there.

If brake bolts, like the Lambert/Viscount fork and the Ava bars/stem and the
old Campagnolo Record cranks and myriads of cycle spokes, have any tendency
to failure, well, then we'd at least hear about it.

No calculations necessary

 

[jim beam]

A Muzi wrote:
> -snip brake bolts-
>
>> jtaylor wrote:
>>
>>> Do you _have_ an example of a cut-thread cycle brake bolt that failed?
>>> That's the issue.
>
>
> jim beam wrote:
>
>> no it's not - it's about the op's dental bills.
>
>
> The comment from one contributor about still riding with a Ballila brake
> (fearless!) pretty much establishes that the dimensions of a 6mm steel
> brake bolt are plenty large to secure a brake to a bicycle. Since we've
> established that all the classic equipment is cut thread

i don't agree with that - my old suntours were definitely rolled. maybe
/some/ obscure manufacturers of /ancient/ equipment cut rather than
rolled, but rolled thread fatigue safety has been with us pretty much
since the old ww1 flying machines.

> and that even
> the worst of those can give 40 years of service, don't you agree that
> any differences are just lost in the noise?

hey, some people don't ride. any equipment can survive that. but
that's not the point - the point is that it needs to be safe for those
of us that /do/ ride, particularly on a front mounted front brake, the
primary barrier between the rider & extreme discomfort. and unlike a
frame where cracking generally becomes evident on inspection and before
failure, brake bolt cracks don't, so it needs to be done right first time.

> Sure rolled threads are a
> better way to go , it's just overkill in this application.

it's not overkill. and the really impenetrably stupid thing about this
argument is that not only are rolled threads better in this app, they're
cheaper in quantity too! there's /no/ reason not to use them! i can't
imagine why people are getting so hot under the collar about defending
inferior, more expensive componentry. there's not even any weight
advantage!

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
>
> > and that even
> > the worst of those can give 40 years of service, don't you agree that
> > any differences are just lost in the noise?
>
> hey, some people don't ride. any equipment can survive that. but
> that's not the point - the point is that it needs to be safe for those
> of us that /do/ ride, particularly on a front mounted front brake, the
> primary barrier between the rider & extreme discomfort.

So - how many front brake bolts have broken?

If the only difference between cut and rolled threads is somewhere around
30%, then SOME should break anyway.

If they don't, then the original poster should have no problems with running
a die down his nutted bolt to use it as a recessed bolt.

 

[jim beam]

jtaylor wrote:
> "jim beam" <[email protected]> wrote in message
> news:[email protected]...
>
>
>>numbers are not something easily calculated. the quickest, easiest way
>>is to test.
>
>
> Wouldn't the best test be what happens in the real situation?

"ladies & gentlemen, thank you for flying plummet air's flight 666 from
diabolo canyon. some of you may have noticed that our wings have just
fallen off and that we're now experiencing a simulated weightless
gravity condition within the cabin. at this time, we request that you
try to keep your personal possessions from floating about as it affects
the debris dispersal pattern on impact and therefore skews the results
of our 'test in real situations' development program we have in
partnership with boeing. we thank you for your cooperation and than you
for flying plummet air."

you don't work in nasa management do you?

>
> Say we have, oh, 100 million cycles out there.
>
> If brake bolts, like the Lambert/Viscount fork and the Ava bars/stem and the
> old Campagnolo Record cranks and myriads of cycle spokes, have any tendency
> to failure, well, then we'd at least hear about it.
>
> No calculations necessary

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> A Muzi wrote:

> > The comment from one contributor about still riding with a Ballila brake
> > (fearless!) pretty much establishes that the dimensions of a 6mm steel
> > brake bolt are plenty large to secure a brake to a bicycle. Since we've
> > established that all the classic equipment is cut thread
>
> > and that even
> > the worst of those can give 40 years of service, don't you agree that
> > any differences are just lost in the noise?
>
> hey, some people don't ride.

Can you tell us how you conclude that

"...are on bike that is ridden often (and has been since I've bought it some
decades ago). Plenty of time
for the fatigue cycles to add up."

and

"...40 years of service..."

translate to

"...some people don't ride."

 

[Frank Krygowski]

jim beam wrote:
>
>
> ... the really impenetrably stupid thing about this
> argument is that not only are rolled threads better in this app, they're
> cheaper in quantity too! there's /no/ reason not to use them! i can't
> imagine why people are getting so hot under the collar about defending
> inferior, more expensive componentry. there's not even any weight
> advantage!
>

The impenetrability is all yours, Jim.

Perhaps you should review the beginning of the thread. The reason _not_
to use rolled threads was that the OP wanted to extend the threading of
an existing bolt using a die. And "an alarmist" claimed that should
NEVER be done.

The original question was not about any "quantity" greater than "one."

ISTM you must never have spent time in a machine shop, where things like
this are done frequently.

- Frank Krygowski

 

[A Muzi]

>> -snip brake bolts-
>>> jtaylor wrote:
>>>> Do you _have_ an example of a cut-thread cycle brake bolt that failed?
>>>> That's the issue.

>> jim beam wrote:
>>> no it's not - it's about the op's dental bills.

> A Muzi wrote:
>> The comment from one contributor about still riding with a Ballila
>> brake (fearless!) pretty much establishes that the dimensions of a 6mm
>> steel brake bolt are plenty large to secure a brake to a bicycle.
>> Since we've established that all the classic equipment is cut thread
>> and that even the worst of those can give 40 years of service, don't
>> you agree that any differences are just lost in the noise?
>> Sure rolled threads are a better way to go , it's just overkill in
>> this application.

jim beam wrote:
> i don't agree with that - my old suntours were definitely rolled. maybe
> /some/ obscure manufacturers of /ancient/ equipment cut rather than
> rolled, but rolled thread fatigue safety has been with us pretty much
> since the old ww1 flying machines.
> hey, some people don't ride. any equipment can survive that. but
> that's not the point - the point is that it needs to be safe for those
> of us that /do/ ride, particularly on a front mounted front brake, the
> primary barrier between the rider & extreme discomfort. and unlike a
> frame where cracking generally becomes evident on inspection and before
> failure, brake bolt cracks don't, so it needs to be done right first time.
> it's not overkill. and the really impenetrably stupid thing about this
> argument is that not only are rolled threads better in this app, they're
> cheaper in quantity too! there's /no/ reason not to use them! i can't
> imagine why people are getting so hot under the collar about defending
> inferior, more expensive componentry. there's not even any weight
> advantage!

I'm sorry if I was unclear.

I am _not_ defending anyone. Just reporting from the field.

As a matter of fact I had never given this a moment's
thought until you brought it to my attention here. Hmmm. I
grabbed a magifier and started opening parts drawers and
found rolled threads to be a rarity - even cut threads on
Shimano, the most automated, most
best-engineering-practices-conscious supplier in the
business. And I recall exactly one instance of failure - a
Drake (India) Phillips type center bolt which aced a
colarbone for a mechanic here in 1974 on a test ride.

If we were co-kings of the world, and if anyone asked, we
would both respond that rolled are better. So what? Uh, I
guess we can say we have a solution should any problem
happen along.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[jim beam]

A Muzi wrote:
>>> -snip brake bolts-
>>>
>>>> jtaylor wrote:
>>>>
>>>>> Do you _have_ an example of a cut-thread cycle brake bolt
>>>>> that failed? That's the issue.
>
>
>>> jim beam wrote:
>>>
>>>> no it's not - it's about the op's dental bills.
>
>
>> A Muzi wrote:
>>
>>> The comment from one contributor about still riding with a
>>> Ballila brake (fearless!) pretty much establishes that the
>>> dimensions of a 6mm steel brake bolt are plenty large to secure a
>>> brake to a bicycle. Since we've established that all the classic
>>> equipment is cut thread and that even the worst of those can give
>>> 40 years of service, don't you agree that any differences are
>>> just lost in the noise? Sure rolled threads are a better way to
>>> go , it's just overkill in this application.
>
>
> jim beam wrote:
>
>> i don't agree with that - my old suntours were definitely rolled.
>> maybe /some/ obscure manufacturers of /ancient/ equipment cut
>> rather than rolled, but rolled thread fatigue safety has been with
>> us pretty much since the old ww1 flying machines. hey, some people
>> don't ride. any equipment can survive that. but that's not the
>> point - the point is that it needs to be safe for those of us that
>> /do/ ride, particularly on a front mounted front brake, the primary
>> barrier between the rider & extreme discomfort. and unlike a frame
>> where cracking generally becomes evident on inspection and before
>> failure, brake bolt cracks don't, so it needs to be done right
>> first time. it's not overkill. and the really impenetrably stupid
>> thing about this argument is that not only are rolled threads
>> better in this app, they're cheaper in quantity too! there's /no/
>> reason not to use them! i can't imagine why people are getting so
>> hot under the collar about defending inferior, more expensive
>> componentry. there's not even any weight advantage!
>
>
> I'm sorry if I was unclear.
>
> I am _not_ defending anyone. Just reporting from the field.
>
> As a matter of fact I had never given this a moment's thought until
> you brought it to my attention here. Hmmm. I grabbed a magifier and
> started opening parts drawers and found rolled threads to be a rarity
> - even cut threads on Shimano, the most automated, most
> best-engineering-practices-conscious supplier in the business. And I
> recall exactly one instance of failure - a Drake (India) Phillips
> type center bolt which aced a colarbone for a mechanic here in 1974
> on a test ride.
>
> If we were co-kings of the world, and if anyone asked, we would both
> respond that rolled are better. So what? Uh, I guess we can say we
> have a solution should any problem happen along.

andy, you must have missed the other thread titled:

"Rolled vs. cut threads (was about brake bolt modification...)"

please read, because in it i outline the differences between rolled &
cut threads, with pics of a shimano 600 brake pivot bolt. certainly, no
shimano brake bolt made subsequent to that has cut threads. if after
reading that you /still/ think shimano use a cut thread, you need to
post a pic of what you have because i've never seen them do it. and
i've been using shimano for some decades now. the thread having the
same nominal diameter as the shaft is *NOT* evidence of cut thread -
contrary to what seems to be a disturbingly popular false assumption.

 

[jim beam]

Frank Krygowski wrote:
> jim beam wrote:
>
>>
>>
>> ... the really impenetrably stupid thing about this
>> argument is that not only are rolled threads better in this app, they're
>> cheaper in quantity too! there's /no/ reason not to use them! i can't
>> imagine why people are getting so hot under the collar about defending
>> inferior, more expensive componentry. there's not even any weight
>> advantage!
>>
>
> The impenetrability is all yours, Jim.
>
> Perhaps you should review the beginning of the thread. The reason _not_
> to use rolled threads was that the OP wanted to extend the threading of
> an existing bolt using a die. And "an alarmist" claimed that should
> NEVER be done.
>
> The original question was not about any "quantity" greater than "one."
>
> ISTM you must never have spent time in a machine shop, where things like
> this are done frequently.
>
> - Frank Krygowski

what's your problem krygowski, the math-free engineering prof? have
nothing technical to contribute, as usual? you want to get a dig in
regarding shop practice, as if to imply i don't have any? bring it on
frank. let's see what you have to offer.