Cutting down a threaded 1" steel fork

Why not make it threadless. I cut down one of my threaded steel forks for
one of my wife's bikes. I ride 61cm frame and she rides 49cm, so I made it a
threadless setup.

Cutting threads from scratch on a steel steerer isn't easy. I've done it a
couple of times to add 1/4" of thread or so when there wasn't quite enough
on the fork, and it took quite a while just to add that much. That was using
the tool and die from the Campagnolo toolchest.

Nick

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

Quoted message said:

I'm putting a handsome new fork with cantilever bosses onto an older
steel road frame. The fork steerer needs to be cut down, to below the
point where the threads begin on it now.

clumsymechanic said:

I'm putting a handsome new fork with cantilever bosses onto an older
steel road frame. The fork steerer needs to be cut down, to below the
point where the threads begin on it now.

It should be pretty easy to cut off the steerer with a tubing cutter,
and I imagine that the appropriate die would cut new threads without
too much fuss (which size exactly?) but before the new threads go on I
would need to dig a new groove for the tab on the non-rotating headset
washer.

How does one do that? A file or dremel attachment? Appreciate tips on
tools and techniques.

Thanks guys,

clumsymechanic

First, cut the threads before you cut off the steerer...The threads
MUST be parallel to the fork crown seat...they are now. If you cut off
all the threads, and then try to cut new threads, no guarantee they
will be parallel w/o a lathe.

Second, DO NOT cut a slot in the fork steerer. file the 'bump' out of
the washer, NO NEED to have a washer with a slot, it does nothing but
tear up threads on forks. It does NOT keep HS adjusted.

clumsymechanic said:

I'm putting a handsome new fork with cantilever bosses onto an older
steel road frame. The fork steerer needs to be cut down, to below the
point where the threads begin on it now.

Quoted message said:

It should be pretty easy to cut off the steerer with a tubing cutter,
and I imagine that the appropriate die would cut new threads without
too much fuss (which size exactly?)

Most decent threaded steerer tubes are butted, and you will be cutting new
threads on the thinner section of the tube. Not a good idea. If the tube
is not butted, then I guess it would be possible to do. There are
special-purpose dies for that.

Quoted message said:

but before the new threads go on I
would need to dig a new groove for the tab on the non-rotating headset
washer.

Don't bother. Grind off the tab instead. Those washers do nada, and the
groove weakens the fork.

--

David L. Johnson

__o | "A foolish consistency is the hobgoblin of little minds, adored
_`\(,_ | by little statesmen and philosophers and divines." --Ralph Waldo
(_)/ (_) | Emerson

David L. Johnson said:

Most decent threaded steerer tubes are butted, and you will be cutting new
threads on the thinner section of the tube. Not a good idea. If the tube
is not butted, then I guess it would be possible to do. There are
special-purpose dies for that.

Quoted message said:

David L. Johnson

The butted-thicker-portion of the steerer is brazed into the fork
crown.
Phil Brown

clumsymechanic said:

I'm putting a handsome new fork with cantilever bosses onto an older
steel road frame. The fork steerer needs to be cut down, to below the
point where the threads begin on it now.

It should be pretty easy to cut off the steerer with a tubing cutter,
and I imagine that the appropriate die would cut new threads without
too much fuss (which size exactly?) but before the new threads go on I
would need to dig a new groove for the tab on the non-rotating headset
washer.

How does one do that? A file or dremel attachment? Appreciate tips on
tools and techniques.

First, don't shorten the tube until the threads have been cut. The
thread size is one that's used only on bikes. Some larger and/or
better-equipped bike shops will have the special die required, but be
aware that there are significant variations in the quality of the
threading dies sold in this size. A shop that's using a cheap, crummy
die will end up cutting poor threads. They may still work, even if
they're obviously ugly, but if they are cut badly enough, the fork
will be junk...and it's easy to have this happen.

Second, don't extend the slot until the fork has been test-fitted, and
then extend it only to the second or third thread below where the tab
will ride; you don't need it any farther down, and the slot weakens
the tube. I've used a Dremel to do this once, but I prefer to use the
edge of a flat file I have. It's slow, but it makes a nice straight
groove and allows good depth control.

Third, don't use a tubing cutter to shorten the tube. Once the tube
has been threaded, a tubing cutter will try to follow the thread
groove, with undesired results. Use a hacksaw, employ a steerer
cutting jig if one is available, and dress the end with files.

Good luck!
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

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

Quoted message said:

I'm putting a handsome new fork with cantilever bosses onto an older
steel road frame. The fork steerer needs to be cut down, to below the
point where the threads begin on it now.

It should be pretty easy to cut off the steerer with a tubing cutter,
and I imagine that the appropriate die would cut new threads without
too much fuss (which size exactly?) but before the new threads go on I
would need to dig a new groove for the tab on the non-rotating headset
washer.

How does one do that? A file or dremel attachment? Appreciate tips on
tools and techniques.

Thanks guys,

clumsymechanic

Go threadless if you can. This is one of the best developments in
cycling to come along in 100 years.

I've built and/or replaced lots of forks. The threaded portion of
steering tubes is the weak link in a bicycle frame. The sharp V at the
bottom of the threads can create a stress riser and cause a crack which
will result in a failure. I've had 2 steering tubes fail while test
riding customer's bikes. It doesn't happen very often but it's no fun if
it does.

If you do rethread the steering tube, make sure that it's done with a
premium threading die like a Campy or Var (maybe Park also).

Chas.

So I guess I'm looking around for a shop with the right die to extend
the threads, and forgetting about the groove.

I'll think about going threadless, but I already have a stem that I'd
like to stick with. Are threaded steerers really that unsafe?? I don't
see a lot of stress at the threaded part, and even if it did break the
stem is stuck in the lower, unthreaded portion of the tube. Anyway
cross your fingers that I survive this bike with all my (remaining)
teeth, and thanks for the help!

clumsymechanic

Quoted message said:

I would need to dig a new groove for the tab on the non-rotating
headset washer.

File off the tab in the washer, that's what I'd do.

- Don Gillies
San Diego, CA

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

Quoted message said:

So I guess I'm looking around for a shop with the right die to extend
the threads, and forgetting about the groove.

I'll think about going threadless, but I already have a stem that I'd
like to stick with. Are threaded steerers really that unsafe?? I don't
see a lot of stress at the threaded part, and even if it did break the
stem is stuck in the lower, unthreaded portion of the tube. Anyway
cross your fingers that I survive this bike with all my (remaining)
teeth, and thanks for the help!

clumsymechanic

Loosen your stem so that it's free to turn in the steering tube. Now try
riding.... NO! STOP!

Bad advice!

The wall thickness of the steering tube at the bottom of the threads is
less than .042" (1.07mm).

Thread height per side for 24TPI = .041666 x 2 sides = .08333.

1" Diameter Thread - .08333 = .91667 diameter at bottom of thread

..91667 -.875 internal diameter of steering tube = .04167 or less wall
thickness in an area prone to stress risers!

In a properly assembled bike where the stem has always been tightened
below the threaded section of the steering tube and the tube is made
from a high quality alloy steel like Reynolds, Columbus, Tange, 4130
Chro-Mo etc. there are rarely problems with thread breakage.

Bikes that have been ridden for a long time with a loose headset or
where the stem has been locked into the threaded area on the steering
tube or for many other reasons can crack or fail at the threads.

During the 70s, I saw many name brand bikes where the manufacturers
substituted high alloy steering tubes with cheap steel tubes, even
worse, some were made from seamed tubing! What does a Columbus or
Reynolds steering tube cost - less than a $1.00!

Broken steering tubes are pretty rare on modern quality bikes but make
sure that you inspect or have someone inspect the fork for cracks or
other problems before assembly.

Chas.

clumsymechanic said:

So I guess I'm looking around for a shop with the right die to extend
the threads, and forgetting about the groove.

I'll think about going threadless, but I already have a stem that I'd
like to stick with. Are threaded steerers really that unsafe?? I don't
see a lot of stress at the threaded part, and even if it did break the
stem is stuck in the lower, unthreaded portion of the tube. Anyway
cross your fingers that I survive this bike with all my (remaining)
teeth, and thanks for the help!

clumsymechanic

No they are not unsafe in any way. Threadless was a way for mostly
front shock makers to save money, nothing structural at all. With thin,
light steeres made of stuff other than steel made threadless popular,
still it was about marketing and weight savings, nothing that helped
performance. For Chas...review the video of Hincapie's steerer failure
before you talk about t-less being the 'best innovation in the last 100
years...doubt it is since 1906...

clumsymechanic said:

I'm putting a handsome new fork with cantilever bosses onto an older
steel road frame. The fork steerer needs to be cut down, to below the
point where the threads begin on it now.

It should be pretty easy to cut off the steerer with a tubing cutter,
and I imagine that the appropriate die would cut new threads without
too much fuss (which size exactly?) but before the new threads go on I
would need to dig a new groove for the tab on the non-rotating headset
washer.

How does one do that? A file or dremel attachment? Appreciate tips on
tools and techniques.

I'd thread the column past the point where you intend to trim as it's
often easier to extend existing threads than to start fresh (unless you
have a lathe).

As for the groove, a simple file will suffice. It doesn't have to extend
very far; just past the top nut.

--

John ([email hidden])