So I bought some koni inserts to make custom strut tubes. I purchased a 1.75 I.D. steel tube with an O.D. to fit the standard coil-over sleeve. I was surprised by how heavy it was. 
Couldn't I just make the tube out of aluminum and then cut the coil=over threads on the lathe? It would be much easier to cut the interior threads, easy to weld, and does away with the silly sleeves. It would be a 1.75 ID and a 2.0 OD. ... which makes for some really thick aluminum.
Thoughts? Strong enough?
I used .25 wall aluminum tubing as coil over sleeve spacers for my Challenge car last year. Don't see any reason why cutting your own custom sleeves wouldn't work.
In reply to Stampie:
Just to be clear. I don't want to make sleeves. I want to make the whole tube out of aluminum, and weld ears on it for my hub assembly.
Welded aluminum in that type of load bearing scenario scares me a little- if you do it, definitely go for overkill on the thickness and ensure that your welds are good. The original stuff was steel for a reason.
Its not like there is a bunch of metal there in the OEM configuration. .JPG)
Sure, but it's steel- it'll deform and cycle a lot more before cracking.
1.75 ID X 2.0 OD = .125 Wall
Whether you're threading or welding on it, just sayin'.
It's a lot easier to design and build your own strut tube in steel then aluminum. You would have to use the correct alloy, weld it with the correct rod, and then have it heat treated afterwards. Plus it won't be as strong and prone to cracking at the welded joints. I've seen strut tube "ears" bend due loads on them. Steel will bend, aluminum will break!
With steel you can use a much thinner wall thickness and then just used a thicker section at the top of the strut to do your internal threads. This section could be welded to the thinner part of the tube but I would counter bore the thick section and slip the thinner section in that. Sort of like exhaust pipes fit into each other.
I almost ended up doing this a few years ago when I was looking for "racing" struts for my VW. I happened to come across someone selling some Bilstien threaded body struts and shocks so I went with them cuz it was the "easy" button.
¯\_(ツ)_/¯ wrote: Welded aluminum in that type of load bearing scenario scares me a little- if you do it, definitely go for overkill on the thickness and ensure that your welds are good. The original stuff was steel for a reason.
This. The fully-threaded coilovers on my car are aluminum and the walls are about 0.25" thick, but there are no welds anywhere. The threaded tube is a single piece and the shock internals are bolted and crimped in, and the lower mount is a single piece (could be CNC'd but the price says probably cast and polished 
).
GameboyRMH wrote: could be CNC'd but the price says probably cast and polished
Fyi cnc is way cheaper than casting, i think it was here or maybe another forum someone made a cast intake manifold. He did all the design and most of the casting because it was his line of worke, he said he was 10-20k just into the one straight six manifold.
Otherwise i dont have much to add except a lot of body height adjustable coilovers are aluminum and from a design point are much more sketchy than this idea and work, 9 times out of 10. I say go for it if you over build it but keep an eye on it for fatigue and such.
Without knowing any more specifics, I'd agree that an aluminum threaded sleeve would be just fine. Make sure and cut trapezoidal threads rather than 60° though.
The problem with aluminum is not the tube or the threads cut into the body but the point where you weld the "ears" to the tube and the possibility of failure at that point is the problem.
If the strut is from a design that doesn't use "ears" but were the strut tube slips into a "pocket" on the knuckle then you don't have those issues. My old Ford Contour used this design and I assume many other cars do as well.
Here's one of my coilovers, all made of aircraft aluminum:
Like I said, the lower mount is one piece that threads on:
Since CNC'ing is still expensive, you could weld up a steel lower mount from much thinner metal, it wouldn't be too heavy, unlike that insanely overbuild threaded sleeve.
Hey,
Can you make the sleeves from Aluminum...yes you can.
What is the weight benefit after you have done a bunch of machining?
Should you do it....maybe.
Is the car gonna be driven on the street? If yes..Probably not a good idea.
Will the car be used on an Autocross course, occasionally? Probably OK. If it is used on a HPDE/road course...probably dicey.
It's fun to make components that are rare or expensive in the aftermarket. And it is risky...
Lotsa good advice in this thread. Proceed carefully
Rog
fasted58 wrote: 1.75 ID X 2.0 OD = .125 Wall Whether you're threading or welding on it, just sayin'.
Is there a math error here?
dean1484 wrote:fasted58 wrote: 1.75 ID X 2.0 OD = .125 Wall Whether you're threading or welding on it, just sayin'.Is there a math error here?
and how so?
2.00 OD - 1.75 ID = .250/ 2 = .125 W
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