Singlespeed & Fixed Gear - another freewheel question

I've read a lot about converting a 'threaded' freewheel to a fixie, and I am trying to do just that at the moment. I thought I knew what a freewheel was, but i'm a little in doubt now. What threads on where? My 'freewheel' is an old 6 speed, but it slides onto the hub on a spline type thingy. The ratchet mech. is all in with the sprockets etc.
Is this a threaded freewheel?

Nope, that's called a freehub. The only way to convert that to a fixie is to get a device called the Surly Fixer. Otherwise, it can be easily converted to single speed with a single cog and spacers.

http://www.surlybikes.com/parts/popup_images/parts_prodFixxer.jpg

"Even if it ain't broke, you can still fix it with our Surly Fixxer hub converter. The Fixxer allows you to convert any Shimano cassette hub (except Silent Clutch, 2004 Dura Ace or pre-1997 Dura Ace) into a true fixed-gear. By simply removing the cassette body and replacing it with our adapter, you can use a fixed track cog and lockring for safe coast-free riding. A popular conversion for track racers, spring time trainers, fixed-gear commuters and messengers, the Fixxer includes all parts necessary for installation, including axle, bearing, cones, spacers, and axle nuts. Most converted hubs can be spaced 120, 126, 130 or 135mm, and can even be used with a freewheel if a freewheeling single-speed conversion is desired."

Seems to me you could find a fixed wheel (with a decent hub) for the same price as the Fixxer.

if it slides onto the splined hub, it is a 'cassette'. you can break apart the cassette and use a single cog and use spacers on the hub to make the bike a single-speed. however, you will not be able to turn it into a fixed-gear. the surly converter is available... for, for the price, might as well get a real hub or an entire rear wheel

you can also braze or weld the bearings on the freehub carrier to make it fixed.

i'm new to this but i really want to learn.. i was reading this.. and wondered if there are any pictures of what the threaded part looks like.. and the "freehub carrier" and what it would look like if it were welded.. and splined hubs and things?

Freehub + Cassette:

http://www.parktool.com/images/repair_help/frhub_2.jpg

Freewheel Hub + Freewheel: Note the threaded hub, where the freewheel threads onto

http://www.parktool.com/images/repair_help/freewheel_hub.jpg

you have to remove the splined carrier, then weld/braze an open seam on the back of it that looks sort of similar to that black flange part right by that person's thumb. just weld a few spots or drop hot brass in there and it'll seize up the bearings. if you're welding it, it burns up some plastic seals and smell really good. i highly endorse it. my friend did this by welding up an old stupid spinergy spox wheel and it worked great. then he threw on a shimano dx bmx splined cog. bing! eyebrows!

my roommate is going to braze up my rear hub on my trials bike, i just got some front freewheel cranks... i've been told it seems to work a little cleaner than welding.

i'll see if i can find a picture of it on this new fandangled interweb hub... never heard of it myself... the interweb that is.

no real pictures, but a good description of the process:
http://www.63xc.com/mathieson/cheaphub.htm

i also welded up a freehub after grinding into the bearings. it was rock solid …until the freehub splines (steel) ate away the hub splines (alu).

i also welded up a freehub after grinding into the bearings. it was rock solid …until the freehub splines (steel) ate away the hub splines (alu).
fixed rear trials setups run into the same problem, unless you keep the whole cassette on there. the pressure is more evenly distributed with the whole cassette on there i guess. in the back of the newest dirt rag i saw an add for a single cog that has a super wide base, which would help prevent that... i can't think of what it was called though...

edit: i know that spicer was not the ad i saw, but they're making a ti 14mm wide base ss cog... (http://www.spicercycles.com/index.cgi?cat=18&sub_cat=Cogs&prod_id=470&cat_desc=Mountain) it's not cheap though.