Head Tube machining?????????????????
I am looking to build a mountain bike frame, the one part i don't understand is the head tube, i found company's that sell head tubes but they told me they have to be machined in order to fit the headset. I don't understand what they mean by this, cant i just buy a head tube and press the headset into it?
I think your talking about Paragon HT's and they make them undersize so you can ream to fit after welding they do that for distortion. I have machined them to size before welding
Originally Posted by lucahemi
and ream them after welding alot easier on the tool and my hands!!!
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ok thanks, but is there any company's that make them that don't need to be machined at all, so i can just press the headset in?
I don't know about the paragon HT's, but you could just buy some headtube stock (like this one from nova: MTB OS Headtube in CRMO 37.0 dia x 1.6mm wall x 200mm long :: TUBES STEEL :: Nova Cycles Supply Inc. )
You'll probably need to ream it before you press a headset in, but your LBS can do that if you don't have the tools.
You have to face and ream all the head tubes for proper headset installation. The bottom bracket will need the threads chased and the ends faced. There are lots of tools required for this. As someone said earlier, find a good LBS or start buying the tools.
I'm not sure any of this is as important as it used to be, with sealed bearings, ex-bearing cranks, and better components and all, but it still needs to be at least close. Even if you have frame parts that are machined beforehand, depending on where you place your intersecting tubes, how good they fit, and how much heat the tubes see as a result of your welding skills, there will be some amount of distortion that should be squared back up. Dealing with BB threads that are not dead nuts is a recipe for disaster and frustration. You also don't want to have to pound the crap out of a headset cup to get it in your first frame, like... one noob frame builder, um... I know of.
Some frame parts are sized right up to start with, but if you get a lot of distortion, you might not be able to compensate for that with post weld reaming. Paragon allows extra material so the builder has max flexibility to compensate for such anomalies. Which way you go is a choice you make. I think Paragon is pretty smart, and if you find yourself with a lot of distortion after all of that frame building effort, you will likely agree.
Price out a facing/reaming tool set for the BB and HT. You will VERY QUICKLY see the wisdom of finding a good LBS that can do this work for you. My guys have always charged me "a beer" when I have sought this service from them. You might not get quite that lucky, but most shops don't charge much, I don't believe. It would certainly take you many trips to the LBS with many frames to justify purchasing a tool set of your own!
Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
- John Hajny, a.k.a. TrailMaker
Or find a local builder. The bike shops out here charge $50-75 to "prep" a frame (head tube, bb, and disc tabs). Even at $50 youre still almost 30 frames away from paying for the park tools.
$450 for the head tube reamer
$153 for the XL facer
$118 for the 43.95mm reamer
$26 for the cone
$480 for the bb tap/facing system
$145 for the ISO brake facing tool
you're going to have to prep the HT after you build the frame and there's no way around it no matter how skilled you might be with a torch. The tube can ovalize, it can banana and if you "final machine" the HT before you build the frame, you'll likely end up with less than full contact around the circumference of the headset even if you ream and face the HT when you're done.
Originally Posted by lucahemi
Best advice in this thread, IMO.
Originally Posted by RCP FAB
Speciality tools are great, but they're not economically viable for the hobbyist builder.
Hey lucahemi - hobbyist builder here.
I had the same idea you have. My material of choice is carbon, so it turns out that I can actually reach my goal because I don't deal with heat deformation.
I didn't really understand metal weld "pull" until I saw it with my own eyes. Listen to these guys.
Disclaimer: I run Regular Cycles
(as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.