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Stems - Forged v. Casting v. CNC Machined?!?!(10 posts)

Stems - Forged v. Casting v. CNC Machined?!?!Iwannapodiumgirl
Jul 15, 2002 4:06 AM
Whilst I understand the differences in manufacturing techniques which is "best"?

I am not necessarily concerned about weight (to shave grams I will eat less pizza/drink less beer!), but do not wish for the stem to snap (ala Deda Newton!)

You get my vote for best new "handle"....nmDave Hickey
Jul 15, 2002 7:24 AM
re: Stems - Forged v. Casting v. CNC Machined?!?!Crankist
Jul 15, 2002 10:50 AM
Your question mixes mat'l. mfg. and machining mfg. so perhaps you may not fully understand.
I am not familiar with any cast stems. If they exist, then
that's what I'd be sure to avoid. Unless it's an 'investment
casting' the possibilty of voids and inclusions make the idea just plain dangerous.
Forgings, barstock (and castings) are all machined. CNC machining doesn't really offer any advantages over manual machining, except perhaps, lower cost. I see this term used a lot to promote part sales and it's really meaningless. The higher quality stems start with barstock or forged solid billets and machine from scratch. Quality forgings are somewhat tougher than a similar alloy in bar form, but that difference may be meaningless in a stem for normal riders.
Two-piece welded construction can be very solid, but I don't want to be wondering if mine was a Monday AM hangover build.
I suggest spending a few extra bucks on something like Thomson or Cinelli and check the raw mat'l. mfg. type.
The Skinnygrzy
Jul 15, 2002 2:21 PM
You want to avoid things that are primarily CNC'd and go for things that are (net) forged - all other things being equal. Here's why. A CNC stem is simply a billet o' material that's been hogged out to something that looks like a cool stem - completely ignoring the grain structure of the metal. When something is forged the grain structure roughly follows the shape of the object and is typically structurally stronger. if there's something to be learned from MTBs (actually there are many things, but that's another day) is that any one can whip out all sorts of purple anodized CNC stuff that looks really cool and will absolutely fail. Not that CNC stuff can't work - it can, but it needs to be made heavier and more robust as a result. Two interesting examples of decent stems would be from Ritchey and Thomson. The former is net forged while the later is CNC and the differences are reflected in their weights and asthetics.

There is more than one way to make a stem, but it helps to understand the technology and not just look at weight and price.
re: Stems - Forged v. Casting v. CNC Machined?!?!Iwannapodiumgirl
Jul 15, 2002 2:56 PM
I guess those podium girls distracted me long enough to confuse the issues!

So then, is for example, a 3TTT Forgie Stem (forged) "better" than say the ITM Millenium Stem (CNC'd)? These are the options I am thinking of getting to size my Bianchi XL EV2 correctly.
Forging generally stronger than CNC'dKerry
Jul 15, 2002 5:23 PM
The advantage to forging is that you get the grain structure aligned with the dimensions of the part, whereas with CNC you start with a block and cut holes in it. That's not to say that forged parts are ALWAYS better than CNC, but a well done forging will generally be better (strength/weight, durability, etc.).
So, a 3TTT Forgie is necessarily better than...Iwannapodiumgirl
Jul 15, 2002 11:53 PM
a CNC machined stem, such as 3TTT Zepp or ITM Millenium? These are my options I guess.
Re-read my post!Kerry
Jul 16, 2002 4:58 PM
You have to believe that two stems in the same brand line (TTT Forgie vs. TTT Zepp) have different design goals and metrics. To say that forged one is "better" than the CNC unit would only be the case if they came in at the same stiffness, weight, etc. You want a simple answer to a complicated question - it ain't gonna happen.
Jul 16, 2002 5:14 PM
It's NOT a black and white world? ;-b

No matter how you qualify it they still don't get it.
Now I'm scared and confusedIwannapodiumgirl
Jul 16, 2002 5:31 PM
Never suggested that it was clear cut, rather commenting that based on Kerry's post forged is "better" than CNC. Just wanted confirmation? If I'd want a definite opinion, I'd get an ex AA partner on the case (sorry, couldn't resist)