Brian Engelen

Sure, the torque wrench will sense +/- 4%. That is very common.

What the screw manufactures are saying is that the "joint" or system with
the screw will respond +/- 25% when using a perfect torque wrench. This is
due to a long list of things that might happen.

A simple example of this is if the threads are slightly damaged and cause
more friction. The screw will then be harder to turn. The extra torque
required to turn the screw due to the friction is going to give you a false
reading.

-----Original Message-----
From: Eric Chu [mailto:eric@bikemecca.com]
Sent: Wednesday, July 23, 2008 5:14 PM
To: Brian Engelen
Cc: obra@list.obra.org
Subject: Re: [OBRA Chat] Tool envy: torque wrench vs. experienced mechanic

I think you meant the other guy is right.

although I think we're both right to some extent. a lot of things
affect the actual torque you end up with even with the use of a
torque wrench.

Having been in retail as a certified tech and having worked for
continental UCI team, I believe having an accurate torque wrench is a
real asset. I don't feel like paying for a customer's $250 stem out
of my own pocket. I've also seen plenty of techs, with many more
years of experience than I, destroy a lot of the new weight-weenie
stuff.

For the record, the Effetto Mariposa wrench has a stated accuracy of
+/- 4%.

If a leading screw manufacturer says torque wrench's only have +/-
25% accuracy...that's a good reason not to use a mass-market torque
wrench not designed specifically for use on bikes and in the specific
torque ranges used regularly for those componenets. The narrower the
range, the more accurate the wrench.

(and I have not been hired to flog this product)

eric
----------
bikemecca.com
On Jul 23, 2008, at 1:52 PM, Brian Engelen wrote:

> Eric is exactly right.
>
> Torque wrench smork wrench. What kind of accuracy do you think you
> are
> gaining?
>
> I'm not a certified bike mechanic but I do have over 20 years
> experience as
> a mechanical engineer specializing in tool design.
>
> Here is what a leading screw manufacture says:
>
> Torque wrench +/- 25% accuracy
> By feel +/- 35% accuracy
>
> I can send you their documentation if you want it. In fact, I have
> not
> found a recent manufactures publication that lists torque ratings.
> I have
> some old documents that list off a number of requirements that must
> be met.
> The most import is that it must be an unused screw with lubrication
> from the
> factory.
>
>
>
>
>
>
>
> -----Original Message-----
> From: obra-bounces@list.obra.org [mailto:obra-
> bounces@list.obra.org] On
> Behalf Of Eric Chu
> Sent: Wednesday, July 23, 2008 1:03 PM
> To: OBRA chat
> Subject: Re: [OBRA Chat] Tool envy: torque wrench vs. experienced
> mechanic
>
> Sure, a tool is just a tool. And component quality, surfaces and
> bolt prep
> all affect the tension on the threads. The question, in my book, is
> whether
> you are doing the best you can with the tools that are available?
>
> No matter how experienced a mechanic is, torqueing fasteners to very
> specific range consistently is a real challenge, especially with
> all the
> fussy components that are on the market now.
>
> If you took a four-bolt stem faceplate and tightened all the bolts
> by hand,
> and then checked them with a decent torque wrench, I think you'd be
> surprised at how different the tightness was from one another.
>
> Ultimately, I think the bottom line is customer satisfaction and
> trust. and
> unfortuanately, especially for a retail business, liability
> protection.
> Having a reliable tool that is calibrated an established standard
> is waaaaay
> better than saying, "it felt just right" so I don't know why the
> carbon stem
> failed.
>
> so..the best scenario? an experienced mechanic AND a torque wrench.
>
> eric
> ------------
> bikemecca.com
>
>
> --------------------
> Message: 3
> Date: Tue, 22 Jul 2008 13:56:07 -0700 (PDT)
> From: john
> Subject: Re: [OBRA Chat] Tool envy: Effetto Mariposa Giustaforza
> Torque Wrench
>
>>>>>> The main issue: When torque is applied to a bolt, most of that
>>>>>> torque
> (90-95%) goes
> into overcoming friction, only 5-10 % go into preload. That means
> if the
> friction
> is off a little, maybe a little galling / burr,? or maybe slippery
> coating,
> etc,
> the pre-load can be off? whole lot (personal testing, off easily by
> half to
> double
> ! ).? Its actually been shown that a experienced machinist /
> mechanic with
> just
> a normal wrench can be just as accurate. <<<<
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org
>

john

well the way i wrote it,  i left it kind of open..  and never said that wasn't a nice torque wrench... and it is specifically made for bicycles,... i wouldn't see  accuracy as the main advantage, but the other features, as you pointed out.

Mainly wanted to add, to be aware, that the end result wanted is bolt tension, not torque. and this being a large function of friction, which can vary, depending..

In the case of most 5 mm  / 6 mm bolts.. the bolts are pretty standard, the bolt threads are hard chrome or something, the other threads are aluminum, and the guys that come up with the torque values hopefully tested it (they probably torqued to strip then halved or something like that..)  so a known situation..  so anyway the end result in this particular situation is probably fairly accurate.  

so just wanted to raise awareness... Its hard to write this stuff and cover all bases, all situations.. words like "sometimes", "probably" and "might", "maybe" and "can-be", "in my opinion"get heavily used.  and seriously, large books have been written on this subject.

In most bolting situations (non bicycle), Its pretty simple: you tighten the shit out of them. Almost to where they bust.  Most good machinists/mechanics can feel when the bolt starts stretching (ie yielding) and that's where they stop.  This is good and thats good bolted joint. But of course the clamped components need to be accounted for too!  One aspect of good design is typically such that a bolt can be broken before clamped components are warped or stripped or in some other way damaged (in my opinion).  But of course not all design can consider only that factor, and not everyone has the time or the money to do perfect design, and most of the time it probably just doesn't matter and who the hell cares, kind of like all this stuff i am writing. 

Now, this bicycle stuff, especially it appears with this new lightweight stuff, as I am only now realizing / learning about, is quite the opposite in that the bolts are often stronger then the components... Too much torque and you strip threads, crack carbon, etc. 

And then there are things on a bicycle where threads (pedals, bottom bracket)  are used that really aren't used in a manner to hold a preload.  they are still a holdover from before bolted joints were understood.  (bolted joints really weren't widely used ("understood") and thus specified in design of say a bridge until 1950's or so..  i think the Mackinaw bridge in michigan was one of the first big structures to use bolts rather than rivets. (Obviously the physics was probably understood decades before).  One reason I suppose was that the bolts weren't mass produced until until they figured out how to roll the threads.  Prior to that the threads were cut on a "screw-cutting lathe", much more expensive and not near as strong.   Its amazing how much we take them for granted, and few of us realize how much work it took and takes to make those damn little things with the accuracy that they have.

Anyway yes you are right, if someone drops $200 plus or whatever on carbon handlebar / stem or etc.., I sure as hell will be using the torque wrench too.  but first i would try to hand it to hand it off to you.  

--- On Wed, 7/23/08, Eric Chu wrote:
From: Eric Chu
Subject: Re: [OBRA Chat] Tool envy: torque wrench vs. experienced mechanic
To: "Brian Engelen"
Cc: obra@list.obra.org
Date: Wednesday, July 23, 2008, 5:13 PM

I think you meant the other guy is right.

although I think we're both right to some extent. a lot of things
affect the actual torque you end up with even with the use of a
torque wrench.

Having been in retail as a certified tech and having worked for
continental UCI team, I believe having an accurate torque wrench is a
real asset. I don't feel like paying for a customer's $250 stem out
of my own pocket. I've also seen plenty of techs, with many more
years of experience than I, destroy a lot of the new weight-weenie
stuff.

For the record, the Effetto Mariposa wrench has a stated accuracy of
+/- 4%.

If a leading screw manufacturer says torque wrench's only have +/-
25% accuracy...that's a good reason not to use a mass-market torque
wrench not designed specifically for use on bikes and in the specific
torque ranges used regularly for those componenets. The narrower the
range, the more accurate the wrench.

(and I have not been hired to flog this product)

eric
----------
bikemecca.com
On Jul 23, 2008, at 1:52 PM, Brian Engelen wrote:

> Eric is exactly right.
>
> Torque wrench smork wrench. What kind of accuracy do you think you
> are
> gaining?
>
> I'm not a certified bike mechanic but I do have over 20 years
> experience as
> a mechanical engineer specializing in tool design.
>
> Here is what a leading screw manufacture says:
>
> Torque wrench +/- 25% accuracy
> By feel +/- 35% accuracy
>
> I can send you their documentation if you want it. In fact, I have
> not
> found a recent manufactures publication that lists torque ratings.
> I have
> some old documents that list off a number of requirements that must
> be met.
> The most import is that it must be an unused screw with lubrication
> from the
> factory.
>
>
>
>
>
>
>
> -----Original Message-----
> From: obra-bounces@list.obra.org [mailto:obra-
> bounces@list.obra.org] On
> Behalf Of Eric Chu
> Sent: Wednesday, July 23, 2008 1:03 PM
> To: OBRA chat
> Subject: Re: [OBRA Chat] Tool envy: torque wrench vs. experienced
> mechanic
>
> Sure, a tool is just a tool. And component quality, surfaces and
> bolt prep
> all affect the tension on the threads. The question, in my book, is
> whether
> you are doing the best you can with the tools that are available?
>
> No matter how experienced a mechanic is, torqueing fasteners to very
> specific range consistently is a real challenge, especially with
> all the
> fussy components that are on the market now.
>
> If you took a four-bolt stem faceplate and tightened all the bolts
> by hand,
> and then checked them with a decent torque wrench, I think you'd be
> surprised at how different the tightness was from one another.
>
> Ultimately, I think the bottom line is customer satisfaction and
> trust. and
> unfortuanately, especially for a retail business, liability
> protection.
> Having a reliable tool that is calibrated an established standard
> is waaaaay
> better than saying, "it felt just right" so I don't know why
the
> carbon stem
> failed.
>
> so..the best scenario? an experienced mechanic AND a torque wrench.
>
> eric
> ------------
> bikemecca.com
>
>
> --------------------
> Message: 3
> Date: Tue, 22 Jul 2008 13:56:07 -0700 (PDT)
> From: john
> Subject: Re: [OBRA Chat] Tool envy: Effetto Mariposa Giustaforza
> Torque Wrench
>
>>>>>> The main issue: When torque is applied to a bolt, most
of that
>>>>>> torque
> (90-95%) goes
> into overcoming friction, only 5-10 % go into preload. That means
> if the
> friction
> is off a little, maybe a little galling / burr,? or maybe slippery
> coating,
> etc,
> the pre-load can be off? whole lot (personal testing, off easily by
> half to
> double
> ! ).? Its actually been shown that a experienced machinist /
> mechanic with
> just
> a normal wrench can be just as accurate. <<<<
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org
>

_______________________________________________
OBRA mailing list
obra@list.obra.org
http://list.obra.org/mailman/listinfo/obra
Unsubscribe: obra-unsubscribe@list.obra.org

Eric Chu

I think you meant the other guy is right.

although I think we're both right to some extent. a lot of things
affect the actual torque you end up with even with the use of a
torque wrench.

Having been in retail as a certified tech and having worked for
continental UCI team, I believe having an accurate torque wrench is a
real asset. I don't feel like paying for a customer's $250 stem out
of my own pocket. I've also seen plenty of techs, with many more
years of experience than I, destroy a lot of the new weight-weenie
stuff.

For the record, the Effetto Mariposa wrench has a stated accuracy of
+/- 4%.

If a leading screw manufacturer says torque wrench's only have +/-
25% accuracy...that's a good reason not to use a mass-market torque
wrench not designed specifically for use on bikes and in the specific
torque ranges used regularly for those componenets. The narrower the
range, the more accurate the wrench.

(and I have not been hired to flog this product)

eric
----------
bikemecca.com
On Jul 23, 2008, at 1:52 PM, Brian Engelen wrote:

> Eric is exactly right.
>
> Torque wrench smork wrench. What kind of accuracy do you think you
> are
> gaining?
>
> I'm not a certified bike mechanic but I do have over 20 years
> experience as
> a mechanical engineer specializing in tool design.
>
> Here is what a leading screw manufacture says:
>
> Torque wrench +/- 25% accuracy
> By feel +/- 35% accuracy
>
> I can send you their documentation if you want it. In fact, I have
> not
> found a recent manufactures publication that lists torque ratings.
> I have
> some old documents that list off a number of requirements that must
> be met.
> The most import is that it must be an unused screw with lubrication
> from the
> factory.
>
>
>
>
>
>
>
> -----Original Message-----
> From: obra-bounces@list.obra.org [mailto:obra-
> bounces@list.obra.org] On
> Behalf Of Eric Chu
> Sent: Wednesday, July 23, 2008 1:03 PM
> To: OBRA chat
> Subject: Re: [OBRA Chat] Tool envy: torque wrench vs. experienced
> mechanic
>
> Sure, a tool is just a tool. And component quality, surfaces and
> bolt prep
> all affect the tension on the threads. The question, in my book, is
> whether
> you are doing the best you can with the tools that are available?
>
> No matter how experienced a mechanic is, torqueing fasteners to very
> specific range consistently is a real challenge, especially with
> all the
> fussy components that are on the market now.
>
> If you took a four-bolt stem faceplate and tightened all the bolts
> by hand,
> and then checked them with a decent torque wrench, I think you'd be
> surprised at how different the tightness was from one another.
>
> Ultimately, I think the bottom line is customer satisfaction and
> trust. and
> unfortuanately, especially for a retail business, liability
> protection.
> Having a reliable tool that is calibrated an established standard
> is waaaaay
> better than saying, "it felt just right" so I don't know why the
> carbon stem
> failed.
>
> so..the best scenario? an experienced mechanic AND a torque wrench.
>
> eric
> ------------
> bikemecca.com
>
>
> --------------------
> Message: 3
> Date: Tue, 22 Jul 2008 13:56:07 -0700 (PDT)
> From: john
> Subject: Re: [OBRA Chat] Tool envy: Effetto Mariposa Giustaforza
> Torque Wrench
>
>>>>>> The main issue: When torque is applied to a bolt, most of that
>>>>>> torque
> (90-95%) goes
> into overcoming friction, only 5-10 % go into preload. That means
> if the
> friction
> is off a little, maybe a little galling / burr,? or maybe slippery
> coating,
> etc,
> the pre-load can be off? whole lot (personal testing, off easily by
> half to
> double
> ! ).? Its actually been shown that a experienced machinist /
> mechanic with
> just
> a normal wrench can be just as accurate. <<<<
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org
>

Brian Engelen

Eric is exactly right.

Torque wrench smork wrench. What kind of accuracy do you think you are
gaining?

I'm not a certified bike mechanic but I do have over 20 years experience as
a mechanical engineer specializing in tool design.

Here is what a leading screw manufacture says:

Torque wrench +/- 25% accuracy
By feel +/- 35% accuracy

I can send you their documentation if you want it. In fact, I have not
found a recent manufactures publication that lists torque ratings. I have
some old documents that list off a number of requirements that must be met.
The most import is that it must be an unused screw with lubrication from the
factory.

-----Original Message-----
From: obra-bounces@list.obra.org [mailto:obra-bounces@list.obra.org] On
Behalf Of Eric Chu
Sent: Wednesday, July 23, 2008 1:03 PM
To: OBRA chat
Subject: Re: [OBRA Chat] Tool envy: torque wrench vs. experienced mechanic

Sure, a tool is just a tool. And component quality, surfaces and bolt prep
all affect the tension on the threads. The question, in my book, is whether
you are doing the best you can with the tools that are available?

No matter how experienced a mechanic is, torqueing fasteners to very
specific range consistently is a real challenge, especially with all the
fussy components that are on the market now.

If you took a four-bolt stem faceplate and tightened all the bolts by hand,
and then checked them with a decent torque wrench, I think you'd be
surprised at how different the tightness was from one another.

Ultimately, I think the bottom line is customer satisfaction and trust. and
unfortuanately, especially for a retail business, liability protection.
Having a reliable tool that is calibrated an established standard is waaaaay
better than saying, "it felt just right" so I don't know why the carbon stem
failed.

so..the best scenario? an experienced mechanic AND a torque wrench.

eric
------------
bikemecca.com

--------------------
Message: 3
Date: Tue, 22 Jul 2008 13:56:07 -0700 (PDT)
From: john
Subject: Re: [OBRA Chat] Tool envy: Effetto Mariposa Giustaforza
Torque Wrench

>>>>>The main issue: When torque is applied to a bolt, most of that torque
(90-95%) goes
into overcoming friction, only 5-10 % go into preload. That means if the
friction
is off a little, maybe a little galling / burr,? or maybe slippery coating,
etc,
the pre-load can be off? whole lot (personal testing, off easily by half to
double
! ).? Its actually been shown that a experienced machinist / mechanic with
just
a normal wrench can be just as accurate. <<<<
_______________________________________________
OBRA mailing list
obra@list.obra.org
http://list.obra.org/mailman/listinfo/obra
Unsubscribe: obra-unsubscribe@list.obra.org

Eric Chu

Sure, a tool is just a tool. And component quality, surfaces and bolt prep all affect the tension on the threads. The question, in my book, is whether you are doing the best you can with the tools that are available?

No matter how experienced a mechanic is, torqueing fasteners to very specific range consistently is a real challenge, especially with all the fussy components that are on the market now.

If you took a four-bolt stem faceplate and tightened all the bolts by hand, and then checked them with a decent torque wrench, I think you'd be surprised at how different the tightness was from one another.

Ultimately, I think the bottom line is customer satisfaction and trust. and unfortuanately, especially for a retail business, liability protection. Having a reliable tool that is calibrated an established standard is waaaaay better than saying, "it felt just right" so I don't know why the carbon stem failed.

so..the best scenario? an experienced mechanic AND a torque wrench.

eric
------------
bikemecca.com

--------------------
Message: 3
Date: Tue, 22 Jul 2008 13:56:07 -0700 (PDT)
From: john
Subject: Re: [OBRA Chat] Tool envy: Effetto Mariposa Giustaforza
Torque Wrench

>>>>>The main issue: When torque is applied to a bolt, most of that torque (90-95%) goes
into overcoming friction, only 5-10 % go into preload. That means if the friction
is off a little, maybe a little galling / burr,? or maybe slippery coating, etc,
the pre-load can be off? whole lot (personal testing, off easily by half to double
! ).? Its actually been shown that a experienced machinist / mechanic with just
a normal wrench can be just as accurate. <<<<