Alloy headset press fit tolernaces

[M_Chavez]

Hi All,

I've got an alloy 1 1/8" frame and a 1" threaded fork that I want to put together, so I figured I'd ask a friend with a lathe to turn a wee headset adaptor.

The frame head tube must be a bit worn, as it seems to measure between 34.00 and 34.05 ID.
I can get a very cheap cheap alloy 1" threaded headset with a ~29.95mm cup to plug into the adaptor. It's not a "proper JIS, so the race will fit the fork fine.

What ID and OD shall I specify for the adaptor and how much wiggle room do I have? I am thinking 34.10 for OD and 29.90 for ID, but would welcome any suggestions...I guess it's better to loctite a loose adaptor in, than crack the frame trying to push in an oversized cup. If my measurements are off, how likely am I to be able to push in a 34.10 cup into a 34.00 frame?

Thanks.

 

[Jonny69]

You'll never get it in with a 0.1mm difference! I was about to say 0.05mm but I'm way rusty on this and press fits look like they are closer to 0.01-0.025mm. The main problem might be the sleeve compressing, so while it might press fit into the head tube, it might then be too small to get the headset cups into. You might need to press the sleeves onto the headset cups first, then check the size and turn them to the correct size for the press fit into the head tube.

Another option might be to measure measure measure and make a sleeve 0.025mm thicker than the gap. Cut a slot through it so it'll slide fit on the cup and then press it in. That's how I've done headset shimming with shim strip in the past, which was matching a standard 1" headset to a Russian head tube which was 0.2mm larger diameter than normal.

 

[mdvineng]

0.1mm is the normal interference fit for 1 inch or 1 1/8th

 

[M_Chavez]

Thank you very much - cutting a slot (and soaking in loctite/epoxy?) is a smart idea if it doesn't want to go in.

I found this parktool reference that shows 0.1-0.25 (!!!) as being acceptable. I thought 0.2 was way way too much.
https://www.parktool.com/blog/repair-he ... et-service
See reference at the bottom of the page.

Also, I am guessing that freezing the parts before installation should give some wiggle room? I remember doing that when I had to press-fit some bearings onto an old wood planer.

 

[M_Chavez]

Jonny - what was the Russian tube? HVZ?

The gap is a whopping 4mm, as I'm trying to fit a JIS cup into a 1 1/8 tube lol.

 

[jordic1968]

There are specific headsets for 1" threaded forks and 30mm ID like "NECO 1" Threaded 30mm" and others, maybe that's the simpler solution

 

[M_Chavez]

There are specific headsets for 1" threaded forks and 30mm ID like "NECO 1" Threaded 30mm" and others, maybe that's the simpler solution

I'll need a fair amount of epoxy to fit that into a 34mm headtube!

 

[jordic1968]

Re:

Ops. Right , got confused but what about a ritchey logic ec34/... ?

 

[M_Chavez]

I can only see threadless ones for 1 1/8?

Just to be clear, I am trying to match a 1 1/8" headtube with a threaded 1" fork, because I happen to have a very nice fork for this frame and I am a tight b.stard =) There are commercial adaptors available for 1 1/8 to 1" ISO, but by the time I've paid for the adaptor + an alloy 1" ISO headset, It will be twice as much as I've paid for the frame and the fork lol.
It's yet another bike for the kids at the end of the day, so I'm keeping the budget low and just having some fun building it up with them.

 

[jordic1968]

got it
I was refering to this one selling for 11 euro: https://www.bike24.com/p217226.html