Puget Pounder

Can you run an english die through an italian threaded steerer to convert the threads to english?

My scenario: I need a fork's italians threads extended. I have an english headset to use. If I were to get it extended I thought I might as well go English. The fork would be an italian fork going on an non-italian frame anyways.

2nd question: If the steerer is chromed, do you see any issues with using a wire wheel to take some chrome off the steerer so it's easier on the tools?

My co-op has the tools for me to do this, but I worry that the die is a little run down. I'll have to double check.

onespeedbiker

1) Italian threads and English are so similar, you can simply thread the English race on the steerer and with a little more resistance than normal it will work. #2 using a wire wheel to remove the chrome is common for those than want to preserve their dies to more than one use..

fietsbob

My Sutherland's reference book says Same 1" x 24tpi..

lots of cutting oil and just turn the tap handle an 8th~1/4 of a turn into new material
and then turn it back ,
clear the chips .. then advance another 8th, repeat.

Puget Pounder

I realize that. I know that they are the same TPI, but they are cut at different angles. Was wondering if passing over an English die would safely cut.

fietsbob

Footnotes? references? can you quote your source on that?

Puget Pounder

You seem eager to prove me wrong for some reason. I've seen it mentioned on this forum a hand full of times and it's listed on sheldon brown. https://sheldonbrown.com/headsets.html.

EDIT (adding information): Italian threading is a curious mixture of metric and British. Diameters are specified in millimeters, but threads are in threads-per-inch! In addition, the thread angle is 55 degrees, as with the obsolete British Whitworth system, rather than 60 degrees as with U.S. and metric threads.

https://sheldonbrown.com/gloss_i-k.html

HillRider

See Google for details but Italian threads have an included angle of 55° while SAE and Metric threads have an included angle of 60°. Otherwise English and Italian freewheel and steerer threads have identical diameters and thread pitch.

FBinNY 

Can't give you a citation, but they are different. British threads are 1"x24tpi with 60° flanks, and the crests cut off flat. Italian threads are 25.4mm X 24tpi, with 55° flanks and rounded crests and roots. There's also a small difference in pitch diameter.

Sometime in the seventies or eighties, most Italian makers abandoned the 55° thread form and changed to the British standard, which later became the ISO standard.

The difference is subtle, but can account for tight or sloppy fitting headsets depending on the actual tolerance. But yes, it is safe to extend this with a British die, but you might need to use down pressure if the die is sloppy, otherwise the die pushes back making the first new thread have a short pitch. This won't be a problem if you're extending enough that all the old part is cut off, or if it ends up between the cup and locknut, but can be an issue, possibly causing stripping if it ends up in the locknut.


--------------------

As for using a wire wheel to strip the chrome, that's a hard way to do it with very high risk of flakes and shards flying off into your face. Wea full coverage safety goggles (not just the typical type that look like eyeglasses). My preferred technique for removing chrome is to use medium grit emery cloth like a shoeshine rag down to bare steel, followed by a light pass with a wire brush (or wire wheel) to ensure that there's no embedded grit. Use plenty of sulfurized cutting oil, and clear chips and you should be OK.

BTW- be careful when backing off the die, this is when most end up messing up their newly completed job. If you meet resistance backing off, you've run over and trapped a chip. Stop immediately, turn forward until it's free, flush with cutting oil, and come back off anew. Because the chrome-moly of a fork steerer is a "long chipping" material, and because breaking the attached chip off is where the problems are most likely, I suggest not breaking the chip as often. Continue threading forward until you begin to feel increased resistance, or see chip loading in the die. Then break off the chip, by backing off the die until the back edge is against the chip, then snap it off sharply. Clear the chips ans start forward anew.

Puget Pounder

Thanks, your post was very helpful. It's all a moot point because I lost the auction for the fork. It was made within this decade, so you are saying that it was probably English to begin with?

I'm still going to have to thread a fork that I am buying so this has been bookmarked

fietsbob

[thread details might be useful to others , so I thought why was good
addition to .. Opinions]

There is, I know, a Whitworth british thread and a British standard thread,
Fine and Coarse
to add to the complication, but I don't think it all applies to bicycles..


FWIW..
https://en.wikipedia.org/wiki/British_Standard_Whitworth

FBinNY 

It isn't complicated, there are 2 similar but different fork threads, plain and simple. If you still don't think it applies to bicycles, feel free to believe that, but you're wrong.

fietsbob

Raleigh went with 26tpi for a while. .. but IDK if it was also whitworth.


back to the popcorn

JohnDThompson 

Credit: Sutherland's 4th edition

FBinNY 

No, it isn't Whitworth, it's BSC (British Standard, Cycle) and has 60° thread form.

BTW- there's no need to think, guess, imagine, or remain ignorant. The information is readily available with even the most cursory internet search.

FBinNY 

Note: the sketch in Sutherlands is only an approximation. In practice roots are ways deeper than crests are tall (except for dry seal threads). That's to ensure that there'll never be crest-to-root contact which would create stress risers. Threads are made so that all contact is on the flanks, which is why the only accurate way to measure a thread diameter is to measure the pitch diameter, using either a thread micrometer or using the wire method.

fietsbob

Cool