1" headset threading, help me clear up the mess in my head

[Brucey]

if you look on the 'cyclebasket' website it shows what I think is tange-seiki's interpretation of the ISO 1" headset standard. It clearly says 30.0 mm for the cups. Any time I have a headset that is a slack fit, the epoxy resin comes out. In fact I think all headsets should be a sliding fit or worse, then bonded into place using adhesive. This way the headset can always be fitted without stress (or preload if required).

[DiTBho]

if you look on the 'cyclebasket' website it shows what I think is tange-seiki's interpretation of the ISO 1" headset standard. It clearly says 30.0 mm for the cups.

Yup, seen here, and it made confused because EC30 should have 30.2mm for the cup as "measured diamester" on the cup.

According to the above table, there are "interpretation", and Tange's one reports 30.0mm, which is different from what Sheldom reports, and here there is a lot of confusion and contradiction.

EC30 should be ISO to avoid interpretation, but then from company to company ISO has interpretations?!?
W___T___F___?___!___?

Any time I have a headset that is a slack fit, the epoxy resin comes out. In fact I think all headsets should be a sliding fit or worse, then bonded into place using adhesive. This way the headset can always be fitted without stress (or preload if required).

I've always wondered:

• how to remove the headset fixed with resin in that case? With what chemical product and mechanical process?
• why not use the same technology with which the bottom bracket is made, i.e. thread the inside of the headtube both above and below, and both the cups of the headset? In this way no interference would be needed, and disassembly would be much more practical.
• why not use a temperature gap of 50 degrees and exploit the thermal expansion of metals? e.g. placing both the cups in the freezer at -10C, and heating the head tube to 40 degrees with a heater. This way you wouldn't need tons of pressure for the press. The cups would fit almost as if there wasn't even interference, and once at room temperature they would be fixed.

[DiTBho]

I think all headsets should be a sliding fit or worse, then bonded into place using adhesive. This way the headset can always be fitted without stress (or preload if required).

Do you think this is a preblem for "thin" 80s headtube titanium design like in SpeedWell Titalite?

They are neither Litespeed' nor Raynolds' tubes, and the headset tube is very thin, much thinner than anything built in the 90s when titanium bike frames still had the same geometry and thicknesses as the old steel bikes of the 80s.

I'm quite worried, that frame is not mine, it's very rare, and the diameter of the headtube is 29.9mm. I'm almost tempted to mill out +0.1mm, not to use the press, but a sliding fit without interference, in this case. But... should use adhesive? Which one?

[rogerzilla]

The 30 in EC30 is shorthand (and stupid, given that JIS is exactly 30mm and not EC30).

I did some measuring. Tange ISO cups are just over 30.2mm - about 30.24mm. The "raspberry" of a Cyclus headset reamer is just under 30mm and probably produces a hole very near to 30.0mm when you allow for rotating clearance. So the cups are close to 30.2mm and the frame is tighter to give the interference fit.

Fork crown races are similar - the race is 26.4mm ID (or just under) and the crown race seat is cut to about 26.5mm.

The OP was asking about Italian threading and this is compatible with ISO for practical purposes. The pitch and major diameter are the same but the thread angle is slightly different. It's a "type B" fit which means you shouldn't swap between one and the other. It's not as big as the thread angle difference between, say, M6 and 0BA.

[Jezrant]

As I said above, folks have been fitting ISO threaded headsets to vintage Italian framesets for years without any drama. I fitted a Tange on my 1980 Colnago Super. £20 headset. Looks like an old Record. In the real world, it would be unlikely you'd be swapping back and forth between the old Record headsets and ISO headsets. You'd either be fitting an ISO headset to replace an old worn-out Record headset or refitting an old Record headset that's still serviceable.
This thread is like flogging a dead horse.

[Brucey]

..... It's not as big as the thread angle difference between, say, M6 and 0BA.

is it not exactly the same difference?

[Brucey]

....I'm quite worried, that frame is not mine, it's very rare, and the diameter of the headtube is 29.9mm. I'm almost tempted to mill out +0.1mm, not to use the press, but a sliding fit without interference, in this case. But... should use adhesive? Which one?

i your position, I would probably machine headset parts until they were a sliding fit in the frame, then bond them in place using epoxy resin. I have seen so many frames with cracked or distended head tubes, whereas any bonding operation of this sort has been 100% successful.

[DiTBho]

Considering that I am fussily analyzing this stuff because I will necessarily have to disassemble and reassemble the fork between 4 and 5 times a year, as I have a bicycle travel bag that does not accept the frame with the fork mounted.

You have to disassemble and insert the fork into a reinforced behavior on the bottom of the travel bag.

I had a second homemade fork made, with exactly the same thread of the the other fork, just to keep things simple and avoid problems.
It's a NivaCrMo steel 1" fork, they are only 650g more and I have two dedicated compartments in the bag.

I may change my bicycle travel bag, but for now I want to avoid it because it is a size that does not create any problems putting bikes in the hold of planes, even the cheapest ones.

[DiTBho]

then bond them in place using epoxy resin

That's *very interesting* ...
... just in case something goes wrong, or if we want to change the headset, how do you remove the resin or glue?

[rogerzilla]

..... It's not as big as the thread angle difference between, say, M6 and 0BA.

is it not exactly the same difference?

No, 5 degrees' difference for Italian/ISO and 12.5 degrees' difference for metric vs.BA.

[Brucey]

oh yes, i'd clean forgotten (if I ever knew) about the 47.5 deg thread angle in BA.

[rogerzilla]

0BA is pretty rare on bikes - I think the rear lamp bracket on a 1960s Moulton rack is the only example I've seen - and an M6 bolt is quite a loose fit.

2BA is really common as a mudguard eye thread and is easily confused for M5. Most people run an M5 tap through it, finding that an M5 bolt won't quite screw in due to the smaller major diameter of 2BA. The pitch of the two is close enough that it makes no difference over the thickness of a dropout.