Converting a threadless fork to threaded
 

I'm considering buying a Surly 1 inch threadless fork and finding a framebuilder to cut and thread it. Is this a good idea or even feasible?

When I asked a similar question, everyone told me know because a threadless fork is as thick as the thinnest bits of a threaded fork. Put the threading in it and the thinnest bits get too thin to be safe. Or something like that.

25.4mm threaded chromoly steerer tubes usually have ~1.5mm wall thickness on the threaded end (25.4 - 3.0 = 22.4mm, leaving 0.2mm tolerance for a 22.2mm quill stem). The Surly threadless fork steerer has thinner walls and shouldn't be threaded.

http://surlybikes.com/info_hole/faqs...ess_surly_fork

This FAQ on the Surly website answers your question:

OK, thanks

Though I have heard of people cutting off the threadless steerer and welding a threaded steerer on in its place. That may have just been a "yeah that's possible" rather than a "yeah that's practical" thing though.

Probably more cost effective -- not to mention easier -- to simply replace the whole fork with a threaded fork.

Generally, steerers are threaded from stock on a lathe. My guess is that it would be next to impossible to thread it with a die. Spicing the steerer is an option.

Tuz; There are dies available which have a "chaser" that goes into the tube first to guide the cutter and make sure the threads stay aligned (the usual bike tool sites carry them...but spendy!). A skilled person with that tool can do the job well, but they would check the wall thickness first and would find that most threadless forks stem is too thin. Labor to do the job = cost of a new fork that doesn't need threaded.

On the side; While the surley fork is a good one, there are a lot of good enough or maybe better ones even in 1" so my first recommendation to the OP would be just find a fork that fits and don't waste a lot of time and money chopping on a specific one just to keep a brand loyalty...

If the OP would provide more of this thinking on the "why Surly only" question, we could help him more..

/K

It's my understanding that the dies in a bike shop are FAR better suited to extend existing threads than they are to cutting threads in a virgin tube.

Even here (extending existing threads) one can get into trouble. I've seen the new threads being pulled off the steerer during the "cutting" process. Make sure your die is VERY sharp, use lots of cutting oil, back off every 1/4 turn and have a plan "B" in case things don't turn out well. Andy.

Andy -

There are difgferent types of dies 1) "cleanup or chasing" dies and 2) regular cuttung dies. If a LBS has any they probable only have chasers. A well equipped shop would hav both types.

K

I've extended threads a few times and it takes a lot of torque. Without the existing threads as a guide I don't think you can start the cut or cut straight. Perhaps if you manage to cut a long chamfer beforehand... Even with my sharp cutter I could see some galling occurring. Ksisler if you have a pic of the tool you mentioned I'd like to see it!

Most threadless steerers I've used had the correct walls for a quill, it's easy to check. It's kinda silly since it would be nice to have slightly lighter steer tubes.

I have heard this distinction before but never with a list of the common bike industry dies and their type. I have used Eldi, Hozan, Campy (actually at least 3 different dies), Var and Park. My opinions as to their cutting/chasing abilities are almost due to each's sharpness. Do you have any knowledge on these brands WRT chasing or cutting type? Andy.

Quote:

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Originally Posted by Andrew R Stewart (Post 16165978)

I have heard this distinction before but never with a list of the common bike industry dies and their type. I have used Eldi, Hozan, Campy (actually at least 3 different dies), Var and Park. My opinions as to their cutting/chasing abilities are almost due to each's sharpness. Do you have any knowledge on these brands WRT chasing or cutting type? Andy.

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Andy - don't know for sure that current sellers are identifying distinctions well, but for reference recommend start here:http://www.biketoolsetc.com/index.cgi

Now if only they would keep much in stock...


http://www.biketoolsetc.com/index.cg...id=CA-721/5-EL


This is specifically a "bottom bracket cutting tap" to fit the Campy tool to cut new threads into a blank bottom bracket. It would also "chase" to clean up buggered up threads.

http://www.biketoolsetc.com/index.cg...item_id=CU-022

This one is a tap set "with pilot" for "chasing" bottom bracket threads but it won't cut new threads. This is the basic item for cleaning up threads that already exist.I had a set of chasers long back




A look for fork threaders shows several for cutting new threads and a few "die used for repairing damaged fork column threads" with cautions about using them for cutting new threads, such as this one:
"A good thread chaser and repair tool for fork columns, this set comes with one 1-1/8" x 26tpi die with removable brass guides to accommodate all fork sizes. Dies for other fork sizes available separately. Please note: Cutting fork threads can be done but.....beware! Cutting threads is a difficult and risky process at best and should be viewed as a last
alternative in the process of correct replacement fork sizing. We do not guarantee the process and are not responsible for damage that may occur either to forks or dies.

I used to have a fork threading set which had a bullet nosed item that went about 3 inches into the steerer and kept the die straight. Even at that the experience was painful at best. As it only did the old dinky steerers (7/8"?), I didn't mind much what it was stolen along with most of my other old tools. I don't plan on buying any fork threaders... threadless is definately a better solution.

Etc.

/K

Sheldon had a Hybrid, that seems ideal , only the top~inch is cut, for thread, for the top locknut
one would need a second through threaded nut. to do a jam nut combination.. with the threaded lock nut,
then it does the preload.. and then you can use that quill stem that I presume this is all about.

spacers still below the top nut pair, press down on a threadless ,
un weakened by thread cutting steerer tube headset..

It depends on the die stock. Campagnolo's fork die stock (top) is piloted for a 1" steer tube; Hozan's (bottom), designed for multiple diameter steer tubes, is not.

http://www.os2.dhs.org/~john/fork-die-stock.jpg

Thanks for the pic.

Here ya go. http://www.youtube.com/watch?v=HNbJ9dadNYo. Groovy 's fix

That looks like a lot more work than cutting the old steerer off at the top of the crown, line boring the remaining steerer remnants from the crown leaving a straight and true 25.4mm hole, then brazing in a whole new steerer. Am I missing something?

how do you line bore a crown again?

Portable Line Boring machine?

It sure looks to me like it would work.

ok, be cheaper to buy a new fork though.

I have threaded plenty of standard 1" Steel steer tubes without any problem, I use a Campagnolo tool.