Cutting Threaded Steerer

[211dave112]

Hello - I am currently restoring an old Puch bike and the new headset has a lower stack height than the previous one, meaning the lockring can't be screwed down against the top cup (apologies if some of these terms aren't used quite right!).

So essentially I want to cut the steerer - now the threaded part of the fork is long enough so I don't need to worry about getting anything re-threaded, so is it just a case of using a hacksaw (and a jig to ensure a nice even flat cut) and cutting off the 10mm or so excess?

Hopefully the picture below will show what I'm up against....any help greatly appreciated - this is the last bit before it's ready to ride.

[Brucey]

this might sound daft but if I were in your shoes I'd fit some extra spacers under the locknut rather than cut the steerer. The only things that might dissuade me would be if the handlebars were due to be set very low, or if you are concerned about leaving them too high (i.e. that the expander is not well below the threaded section of the steerer, and you can't see the mark).

1" A-Head spacers will work just fine.

cheers

[MartinC]

Put the nut back on it before you cut it so that you can use it to clean up the thread after the cut. Use a cutting guide if you can and tidy the cut up with a file before you use the nut to clean the thread up. Remember that cutting is a one way trip and if you later want to use a headset with a higher stack height you cant put it back so using spacers is an alternative. IIRC Tange headsets don't have a unusually small stack height so the headset you had before must've been quite high, I'd just double check that I'd assembled the bottom race correctly before committing to the cut.

Sorry - cross posted with Brucey

[TonyR]

Echo what everyone else has said about spacers and cutting. If you do cut it remember the old adage measure twice cut once because once you're cut it there is no sticking bits back if its too short. And to get a good cut unless you have a mitre or bench saw with a metal cutting blade, take a strip of paper and wrap it round the steerer to give you a square edge to visually guide your cut. Otherwise you are likely to end up with a slanting cut of varying degree.

[cycleruk]

Fit a spacer and then, if required in the future, there will be no problem fitting a different headset.
I have a spacer on one of my bikes with no issues.

[531colin]

Add the extra spacers.

However, if you really must cut it.......
take the fork right out
put the old threaded headset cup on the steerer to act as a cutting guide....below the cut
Make your cut, tidy it up with a file....to remove the cup .....undo it a bit, reverse it a bit, undo it a bit more, reverse it a bit....etc. to give the best shot at cleaning the thread.

[Mick F]

I cut mine many years ago, I never thought about using spacers, I'd never heard of A Head or even seen any in those days.

My frame was made by Mercian and I specified a Red S headset. All the rage in the Freewheel Catalogue! Some years later, it wore out and I bought a Campag headset and the stack height was lower, so I cut the steerer. I now know that I shouldn't have, but I'm on my third Campag headset since the original Red S. (First headset is still in use on another bike BTW)

I measured the amount to cut off and screwed on a STEEL headset cup. I cut the steerer gently with a hacksaw, then dressed off the cut end and chamfered the threads. Then, with oil, I worked the headset cup up the steerer, and worked it back and forth the make sure the threads were ok. At no time did I take it right off until I was certain it would go back on easily. I cut off only 5mm or so, perhaps less.

Hindsight would tell me to fit a washer or spacer, but it must be 20years since I cut it.

[SimonCelsa]

Hello Dave,

I had the same problem with this frame & forks........

I did not want to cut the steerer so bought various thickness spacers from E-bay (1mm, 2mm, 5mm, 10mm).

Plenty of permutations to get the headset correct, may look a bit 'long' but it rides OK.

Sorry the picture is not the best, think mine was a Tange headset also, I'm on a boat off China at the mo so can't check!!

All the best, Simon

[Brucey]

.... may look a bit 'long' but it rides OK.

a note of caution; if the quill end is so high that it finishes in the threaded section of the steerer, this significantly increases the chances of the steerer breaking.

If you do cut a steerer, the 'threaded race' approach as described above usually works OK, but there is always a risk of leaving a burr that folds back over when the new race is installed and causes a problem.

If you want to do a 'proper job' then I would advise using a large file to remove the main burrs, and then a 60 degree swiss file to clean up the thread valley, the thread flanks and the lead-in just near the cut.

Leaving a skimpy thin lead-in on the thread form is an open invitation to trouble down the line with any cut thread; having shortened thousands of bolts etc over the years I am now somewhat fussy about it; the few that have caused trouble when I did it in a less good fashion caused an awful lot of trouble.

cheers

[211dave112]

Wow...thanks for all the great (and quick!) responses. Given me a lot to ponder before I make my move. I do need the front end quite low on this bike in order for me to be in my ideal position - though a spacer may still be OK.

Rest assured that there will be significant measuring taking place before cutting!

[RickH]

My old road bike came with a low stack headset & steerer cut to fit. After a number of years, I wanted to replace the headset because it was going a little notchy but I couldn't find any that had a low enough stack to fit as a replacement so had to keep the old headset.

Rick.

[Valbrona]

Use the proper tool: http://www.parktool.com/product/threaded-saw-guide-sg-1

[cycleruk]

Use the proper tool: http://www.parktool.com/product/threaded-saw-guide-sg-1

That's a bit expensive just for one saw cut.

[irc]

I don't own any threaded fork bikes so excuse me if I'm picturing this wrong .... but if cutting the threaded section could a square cut be achieved by using two steel cups as guides. One below the cut and one above the cut with a saw blade thickness between them?

[211dave112]

I just wanted to say thanks for the advice - cut it (using a dremel and a little home made jig) and it worked perfectly first time and the bike is up and running.