I think if several builders, Paragon and White Ind all came to Park then reamers would get made!
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1mm is just the reduced wall thickness in the center section, the section that gets reamed and has the cups pressed in will be quite a bit thicker. Columbus headtubes are a swaged tube and have a constant wall thickness.
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Right, 1 mm is the center section. The wall thickness at the ends is 2 mm, which we feel is robust, and eliminates the need for an additional reinforcing ring.
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is there also a way to place a zs44 on the downside of the headtube? to make a integreated headset on the fork sideā¦?
A ZS44 only works with a 1.125 bottom race. You also need to design specifically for this, since the EC44 cup vs ZS44 cup is ~12mm of stack difference.
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I got some IS41-IS47 from paragon, because they look amazing (in my opinion) and generates a well proportioned frame composition (28,6/31,8 tt and 35/38DT) (again in my opinionā¦)
but i feel that both IS41-IS47 are a bit of weird standardsā¦ (also in my oipinionā¦ 
)
in the case is IS41 seems more like an american standard, and my issue is now to get the reamerā¦ I know that investing in Park tools reamer is never a bad investment, but i could eaily and much cheaper get a IS 42 (that actually already haveā¦)
Soā¦ my question, maybe @mark_pmw can answerā¦ did anyone reamed these headtubes to become a IS42? Do you think its possible??
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It may be possible to ream to 42 mm. Thatās at the builderās discretion. Is the rider a 100 kg bull, or a 55 kg ballerina? Rider weight and intended use must be considered as well as the wall thickness and strength of material.
Any builders have experience with this?
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Thanks!
They are all below 90kgā¦ and the use is Gravel/All roadā¦ nothing crazyā¦
From what i see the wall thickness will be about 1,7mm = (45.1 - 41.7)/2 ā¦ It seems thick enoughā¦ specially in such a small areaā¦ and thatā's why Iām considering this optionā¦
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Technically the bearing rests on the 45deg tapered section and does not contact the āwallsā of the headtube. The tapered section is much stronger:
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Yesā¦ also that!!
For now i do not find any reasons for not trying itā¦ ill keep posted when its done!
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Prepare for a good workout
Removing 0.65-0.725mm wall thickness radially and in depth on the tapered section sounds like quite the challenge with a hand powered tool!
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That is trueā¦ but ill probably run over the lathe firstā¦ and the tapered part will keep taperedā¦
ā¦ I really donāt like that whole idea, and am still 50/50 over doing it. Have 5 of themā¦
ā¦ is 300e in a tool or 300 on other toolsā¦ 
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Someone knows how to handle the Columbus hss spirit headtube in lightweight version? Wall thickness on top is only 0,9mm but insert for is 42 has an od of 44mm. So there is missing 0,2mmā¦ any experience what to do? I thinking about to lathe my own bearing seat on topā¦ but mane someone knows the magic?
nopeā¦ 56mm at the bottom and 46mm at the top. so it is ID 44,2. But i solved the problem:)