Re-tapping left pedal crank

Swapping out pedals recently, I’ve destroyed the pedal threads on a left
crank and visibly damaged the threads half the length on another that
seems to be holding fine.

I know they make LH pedal taps, but wonder if upon destroying the
threads if there typically is enough thread left to merit re-threading
with a tap on aluminum cranks.

Anyone had success or failure re-tapping?


--
meb

On Wed, 27 Oct 2004 13:24:22 +1000, meb
wrote:


Swapping out pedals recently, I’ve destroyed the pedal threads on a left
crank and visibly damaged the threads half the length on another that
seems to be holding fine.

I know they make LH pedal taps, but wonder if upon destroying the
threads if there typically is enough thread left to merit re-threading
with a tap on aluminum cranks.

Anyone had success or failure re-tapping?

I've heard of people not even really retapping, but just threading in
a pedal from the backside just to smooth out some galling. Maybe try
that first and then see if the pedal will hold when installed
properly?

JT


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meb wrote:

Swapping out pedals recently, I’ve destroyed the pedal threads on a left
crank and visibly damaged the threads half the length on another that
seems to be holding fine.

I know they make LH pedal taps, but wonder if upon destroying the
threads if there typically is enough thread left to merit re-threading
with a tap on aluminum cranks.

Left arms are usually replaced as they cost less than the
service in most cases.
But indeed a tap might clear slight thread damage. If the
arm must be re-used a steel insert or a helicoil may be set
in it. Find someone experienced in this work and ask
his/her advice.

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

John Forrest Tomlinson wrote:

On Wed, 27 Oct 2004 13:24:22 +1000, meb
wrote:


Swapping out pedals recently, I’ve destroyed the pedal threads on a left
crank and visibly damaged the threads half the length on another that
seems to be holding fine.

I know they make LH pedal taps, but wonder if upon destroying the
threads if there typically is enough thread left to merit re-threading
with a tap on aluminum cranks.

Anyone had success or failure re-tapping?

I've heard of people not even really retapping, but just threading in
a pedal from the backside just to smooth out some galling. Maybe try
that first and then see if the pedal will hold when installed
properly?

FWIW, I'd recommend just replacing the left crank - they're dirt
cheap, and the "cost" of a failure could be spectacular.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame

On Tue, 26 Oct 2004 23:19:55 -0500, A Muzi
wrote:

meb wrote:

Swapping out pedals recently, I’ve destroyed the pedal threads on a left
crank and visibly damaged the threads half the length on another that
seems to be holding fine.

I know they make LH pedal taps, but wonder if upon destroying the
threads if there typically is enough thread left to merit re-threading
with a tap on aluminum cranks.

Left arms are usually replaced as they cost less than the
service in most cases.
But indeed a tap might clear slight thread damage. If the
arm must be re-used a steel insert or a helicoil may be set
in it. Find someone experienced in this work and ask
his/her advice.

9/16x20 is not a Helicoil size that is supplied as an item available
from stock Time-Sert also doesn't supply that size as a stock item.
It might be possible to get them on special order, but it would be
likely to be costly. OTOH, a threaded bushing could be made and
inserted by a number of means; one is simply to tap the hole for a
much larger thread (probably 3/4" NF or 18x1.5mm), cut off a piece of
threaded stock of that size, run it into the hole, pin it in place,
and then drill and tap it to size. This would only work on a crank
that had sufficient meat around the bore to leave it sound after the
rethreading. I've used similar tactics in machinery repairs a few
times; done well, in an appropriate situation, it's a durable and
permanent fix.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Werehatrack wrote:

9/16x20 is not a Helicoil size that is supplied as an item available
from stock Time-Sert also doesn't supply that size as a stock item.
It might be possible to get them on special order, but it would be
likely to be costly. OTOH, a threaded bushing could be made and
inserted by a number of means; one is simply to tap the hole for a
much larger thread (probably 3/4" NF or 18x1.5mm), cut off a piece of
threaded stock of that size, run it into the hole, pin it in place,
and then drill and tap it to size. This would only work on a crank
that had sufficient meat around the bore to leave it sound after the
rethreading. I've used similar tactics in machinery repairs a few
times; done well, in an appropriate situation, it's a durable and
permanent fix.

No need to fabricate such a bushing, this is a standard repair part,
made by ELDI.

See: http://harriscyclery.net/site/page.c...9&Category=817

Although QBP's copy writer calls them "helicoils" they are not actually,
they're solid bushings.

Sheldon "Day Is Done, Gone The Sun..." Brown
+-------------------------------------------+
| Good judgment comes from experience, |
| and experience comes from bad judgment. |
| --Fred Brook |
+-------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

On 2004-10-27, meb wrote:

Swapping out pedals recently, I’ve destroyed the pedal threads on a left
crank and visibly damaged the threads half the length on another that
seems to be holding fine.

I know they make LH pedal taps, but wonder if upon destroying the
threads if there typically is enough thread left to merit re-threading
with a tap on aluminum cranks.

Anyone had success or failure re-tapping?

ELDI makes a reamer/tap and bushing kit for exactly this purpose. It's
probably more than you'd want to spend for a one-off job, but chances are
your LBS has the kit and could do the work for you.

--

-John )

Sheldon Brown writes:

Werehatrack wrote:

9/16x20 is not a Helicoil size that is supplied as an item available
from stock

No need to fabricate such a bushing, this is a standard repair part,
made by ELDI.

See: http://harriscyclery.net/site/page.c...9&Category=817

Although QBP's copy writer calls them "helicoils" they are not actually,
they're solid bushings.

What's the deal with these QBP bushings ?? The right side is brass,
whereas the left side is steel / silver ?? Does anyone know why
different materials are used ??

- Don Gillies
San Diego, CA

On 27 Oct 2004 12:43:38 -0700, (Donald Gillies)
wrote:

Sheldon Brown writes:

Werehatrack wrote:

9/16x20 is not a Helicoil size that is supplied as an item available
from stock

No need to fabricate such a bushing, this is a standard repair part,
made by ELDI.

See: http://harriscyclery.net/site/page.c...9&Category=817

Although QBP's copy writer calls them "helicoils" they are not actually,
they're solid bushings.

What's the deal with these QBP bushings ?? The right side is brass,
whereas the left side is steel / silver ?? Does anyone know why
different materials are used ??

It says brass, but the photo makes me think it's probably yellow cad
plated; that's often mistaken for brass by people who catalog stuff.
It would make sense for them to do something to differentiate the
appearance of the two, and the easiest solution is to use two
different kinds of plating.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Donald Gillies wrote:
-snip- bushings ?? The right side is brass,
whereas the left side is steel / silver ?? Does anyone know why
different materials are used ??


They are both steel. The plating color is different on each
side. Many small parts, such as brake springs, have
variegated plating so you don't mix the left and right ones.

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