Is it possible to retap a 26pti fork steerer to 24pti

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NorwichVelo
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Is it possible to retap a 26pti fork steerer to 24pti

Post by NorwichVelo »

I've got a frame and forks where the forks are raleigh 26pti but the headset is too loose in the frame. A tange levin will fit snug but of course is 24pti. Sounds like a stupid question but can the steerer thread be retapped to 24pti?
Brucey
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by Brucey »

you can recut the thread to 24tpi but it will look dreadful and may not work that well. Per inch of thread, there will be two 'bad spots' where the thread will be useless because the peaks of one coincide with the troughs of the other.

If you have a headset that is OK then I'd suggest that it would be easier to make it fit OK (eg by using epoxy resin to mount the parts in the frame) than to recut the thread.

cheers
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MikewsMITH2
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by MikewsMITH2 »

Yes a friend of mine has done it successfully. If you can find a bike shop with the necessary die. I used an Indian headset on mine. They still use 26tpi! Acceptable but not great quality. ETC also do a 26tpi headset that seems to be available from a few places.
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garygkn
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by garygkn »

26tpi cups perhaps still available like the Indian head set.

I've got a Raleigh the cranks were removed before it came to me it is 120mm rear spacing and the cups look very difficult to remove the axle has a large amount of play but is coteries. I guessing it is 26tpi.
rjb
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by rjb »

Someone posted a tip for checking if it is a 24 tpi thread by offering up a 24tooth hacksaw blade. If the teeth match the threads "bobs your uncle". :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
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MikewsMITH2
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by MikewsMITH2 »

I am fairly sure all Raleighs originally equipped with Cotterless chainsets at the factory, have normal 24tpi bottom brackets. However they may still have 26tpi headsets! This is because some models with the same frame were cotterless and others were cottered.

Of course some owners may have upgraded their bikes to cotterless after purchase by swapping to a square taper axle, in which case they could still be 26 tpi. Bottom brackets can usually be successfully re-tapped to 24 tpi. I have done several. However with a rare or sought after model, it is probably best not to take the risk and to use a threadless bottom bracket, as I have done on my Lenton.
S.O.S - Save Our Steel!
1971 Raleigh Mercury
2010 Condor Fratello
1980 Peugeot Tandem
1989 MBK Aventure MTB
195? Viking Severn Valley
1951 Raleigh Lenton Sports
See them here http://tinyurl.com/Mikewsmiths-Bikes
garygkn
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by garygkn »

That's a useful tip. Thank you both.
The flats on both cups are ultra thin.
I'm going to measure them and see if I can buy a tool to remove them both. My old bike spanners have a flt tool but these don't fit they appear too small.
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MikewsMITH2
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by MikewsMITH2 »

Gary
OK if the cups have 2 flats like these:
http://www.ebay.co.uk/itm/Raleigh-26tpi ... SwB09YKM9T

Then the cups are most probably 26tpi
S.O.S - Save Our Steel!
1971 Raleigh Mercury
2010 Condor Fratello
1980 Peugeot Tandem
1989 MBK Aventure MTB
195? Viking Severn Valley
1951 Raleigh Lenton Sports
See them here http://tinyurl.com/Mikewsmiths-Bikes
Brucey
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by Brucey »

rjb wrote:Someone posted a tip for checking if it is a 24 tpi thread by offering up a 24 tooth hacksaw blade. If the teeth match the threads "bobs your uncle". :wink:


You can do the same thing using a threaded bolt with any given pitch too. This means that it is actually easiest to check if something is 26tpi or not, because all you need is a (solid) 3/8" rear axle, which will be cut 3/8" x 26tpi. If in doubt compare with an M6x1mm (or M10 x 1mm which is most common for a hollow rear axle) threaded part; 26tpi will almost (but not quite) match a 1mm pitch, whereas a 24tpi thread will be mismatched about twice per inch with either.

FWIW in the late 1970s I think there were a few years when there were Raleigh bikes that used cotterless cranksets in 26tpi BB shells. IIRC these used the standard Raleigh cups (with the 'ridge' and no real flange on the RHS) and a '5C' axle (or similar) for the wider-than-usual BB shell.

The standard raleigh 26tpi headset for many years had a distinctive octagonal top nut and a similarly distinctive (again octagonal I think) adjusting race.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Abradable Chin
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by Abradable Chin »

Can't you knurl the outer surface of your current cups so that they fit more snuggly in the head tube?
You could even use the poor man's version using a punch and a hammer.
Csarvelos
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Re: Is it possible to retap a 26pti fork steerer to 24pti

Post by Csarvelos »

From the USA . . . . . yellowjersey.org . . . . do 26tpi bottom brackets

p.s. more Roadster & other Raleigh bits:
http://www.yellowjersey.org/eastbits.html


They post worldwide and have been really helpful to me

Csarvelos
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