Fork crown milling - Newmarket / Cambridge / Bury St Edmunds ?

Bad Machine

In the garage .....
Location
East Anglia
Can anyone direct me to an LBS (Suffolk or Cambs) that can ? My winter project (rebuilding a delta recumbent trike) has me learning on the job - but there are some things I see I can't do at home.

I've discovered my newly-threaded 1" forks for the 20" front wheel appear to be JIS crown dimension; however, the headset on the frame is ISO.
As measured:
Crown race internal dia = 26.3mm
Fork crown dimension o.d = 27.2mm

I could source another 20" wheel fork, ISO. I've also read that dremelling-out the inner diameter of the crown race is not the way to go.......
 

Nigelnightmare

Über Member
Can you not get a JIS headset?
 

Oldfentiger

Veteran
Location
Pendle, Lancs
Just find someone with a centre lathe.
I machined my own fork by holding the steerer in a 3 jaw chuck, then I ground a left handed turning tool to machine the bearing seat to the required dimension.
Ten minute job tbh.
 
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OP
Bad Machine

Bad Machine

In the garage .....
Location
East Anglia
I've been reading up about ISO and JIS headsets: the cups are slightly different sizes, so swapping my existing ISO headset to JIS may not be possible. One is 30.0 mm, the other 30.2mm, and while the difference is small, much has been written about the problems of tyring to use one rather than the other. If I can find someone to cut the crown to the right size, it would be better.
 

midlife

Guru
Try a JIS fork race against your ISO cups on the frame, might match enough to use if same manufacturer. What make is your ISO headset?
 
OP
Bad Machine

Bad Machine

In the garage .....
Location
East Anglia
This is something your local bike shop should be able to do for you. Phone them and ask?
Sadly, my local bike shops said they can't do it.

It's no surprise - I had previously bought a die and stock to cut the additional 1" thread on the steerer tube, because that service is no longer commonly offered by the remaining independent LBS.
 
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OP
Bad Machine

Bad Machine

In the garage .....
Location
East Anglia
Try a JIS fork race against your ISO cups on the frame, might match enough to use if same manufacturer. What make is your ISO headset?
No markings remain on the ISO headset currently fitted to the headtube. Dismantled and cleaned, looks like this - does anyone recognise ?

Headset cleaned 4.jpg


The problem may have been solved with a lengthy trawl of the various cycle forums - I saw lots of posts recommending milling the crown from JIS to ISO, but none actually saying where it could be done. One exception relevant to the UK, happens to be local.

For future reference:
The Cycle Clinic
Unit 5 Clock House Farm
Cavendish Lane, Glemsford
Suffolk, CO10 7PZ

I've left the forks with Malcolm, and will wait to hear when they're ready to collect.

UPDATE: I collected forks the day after the Christmas holidays. All done. Needed a little tidying up round the edges, but fitted the crown race perfectly on reassembly.
 
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MichaelW2

Veteran
When I lived in Suffolk my goto bike shop was Madgetts of Diss. They can handle most things.
 
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