Steerer thread query.

Andrew Webster said:

Came across a problem this evening replacing a headset on one of my
bikes.

The headset cone for the top headset bearing race - the one that
screws onto the steerer was a VERY tight fit, and wouldn't go on more
than a couple of turns.

Is your old fork French? These had more threads per inch than the
modern ISO/Campag standard.

On 30 Jul 2004 13:33:19 -0700, [email hidden] (Andrew

Webster) said:

My problem is when I try to source such a thing. Searches give MC, MF
UNC & UNF - BSW & BSF dies. Which of these do I want? What does it
all mean? (I can't seem to find 1"x24 in any of them)?

Anyone help me out of my confusion?

Andrew Webster

Someone mentioned different thread sizing, so be careful to check that
out. The best bet for finding the typical threading die is something
like this-

http://www.parktool.com/tools/FTS_1.shtml

You might check out chapter 6 of the Barnett's manual to see if there
is any explanation for your problem-

http://www.bikeforums.net/showthread.php?t=38747

On 30 Jul 2004 13:33:19 -0700, [email hidden] (Andrew

Webster) said:

Came across a problem this evening replacing a headset on one of my
bikes.

The headset cone for the top headset bearing race - the one that
screws onto the steerer was a VERY tight fit, and wouldn't go on more
than a couple of turns.

All threads cleaned thoroughly and undamaged.

I tried the same threaded race on another fork (more modern, 1980s)
and it fitted fine. The old threaded race fitted onto this fork, but
was noticeably loose.

I then tried various other headset bits I had knocking around (races
and locknuts). All would fit my "modern" fork, but wouldn't fit my
"old" fork (v. tight) - yet the original parts could be re-fitted by
hand with no problems.

I don't know if 1" steerer threading meant something slightly
different when this bike was built (bike dates early '70s, though
built from stock parts that might have been around since mid '60s),
but it certailny seems that it is threaded somewhat differently (shape
of threads, perhaps?)

I conclude that I need to chase the threads of my old fork with a 1"
die to get a good fit. Presumably 1"x24tpi.

My problem is when I try to source such a thing. Searches give MC, MF
UNC & UNF - BSW & BSF dies. Which of these do I want? What does it
all mean? (I can't seem to find 1"x24 in any of them)?

Anyone help me out of my confusion?

There are a couple of almost-1"x24 headset sizes that it might be,
depending on where and when it was made.

See http://www.sheldonbrown.com/gloss_h.html#headset

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Quoted message said:

On 30 Jul 2004 13:33:19 -0700, [email hidden] (Andrew
Webster) wrote:
<cut>

There are a couple of almost-1"x24 headset sizes that it might be,
depending on where and when it was made.

See http://www.sheldonbrown.com/gloss_h.html#headset

Thanks for this. The fork certainly fits the "French" description
with a filed flat on one side.

After looking at the advice here (and the price of the Park tools) I
decided on a "cheap and cheerful" solution.

I used an old adjustable race as a "die" to re-cut the threads to
"normal". I mounted the race in a vice and screwed in the fork using
a timber baulk between the blades to get the necessary leverage.

I backed off by about half a turn every complete turn, and undid by a
few turns to clean off the threads every four or five turns. Some
material was certainly cut out - witnessed by metal shavings, the
amount of heat generated, and the fact that the original race was a
very loose fit when I finished (the same "fit" as on my newer fork.
The new headset then fitted fine, needed a pair of Stilsons rather
than fingers to do it up, but stiff rather than tight.

Took about an hour all told.

Thanks to all for the useful comments and suggestions.

Andrew Webster

On 30 Jul 2004 13:33:19 -0700 [email hidden] (Andrew

Webster) said:

I don't know if 1" steerer threading meant something slightly
different when this bike was built (bike dates early '70s, though
built from stock parts that might have been around since mid '60s),
but it certailny seems that it is threaded somewhat differently (shape
of threads, perhaps?)

There's more than one ~1" thread. I think Raleigh used 1 x 26 tpi as
well as 1 x 24 tpi, and then there were French threads which were
actually M25 x 1.

-
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Jim Adney [email hidden]
Madison, WI 53711 USA
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