Simple answer yes you can use a "drill" as a mini lathe.
First off you need to decide what drill you want to use or motor.
A hammer drill works best as it has spots for a handle which can be removed and secured to a rig.
As far as motors i have seen them made out of motors from old treadmills.
here are examples;
This one can be made out of parts from the store and will not ruin your drill.
http://www.btinternet.com/~two.mm/articles/fonly/lathe_overview.jpg
This one here is the best but you have to find someone with a broken lathe.
http://www.rolandandcaroline.co.uk/assets/images/lathedrill.jpg
the famous treadmill/ washing machine motor design kinda like the second.
http://www.rolandandcaroline.co.uk/lathe/lathe2a.jpg
Turning the peice of work is not the hard part.
These are used mainly for wood. the main reason is there is no precision movement as you would need to use for metal working.
The hole for the laser is also easy in concept but a bit difficult to setup. all you do is mount a dril bit to the moving head stock or the back and press it up against the peice spinning on the drill. this will help hold the peice and cut threw it. use lots of lube.
http://www.mini-lathe.com/Mini_lathe/Features/lathe.gif
Best way is to set the hole is to set the tail stock back against the peice nice and tight. remeber to have that tail stock on 2 good drawer sildes. have a bolt mounted to a peice of wood behind it and slowly turn it pushing it evenly against the tail stock. this will give you precision depth for your cuts.
honestly i would never make one again. i have made one and in the beggining i hurt myself alot. alot alot. things broke and hit me and cut me. but what you are trying to make is this but out of hard ware parts
Taig Tools - Desktop Milling Machines and Lathes. sub the chuck and big motor for a drill.
this stuff can go for around 200$ on ebay
after parts and time you are looking at and around 150$-350$. 150 is if you are lucky and know where to get your stuff. junk yards are a great place to look.
7" x 10" PRECISION METAL MINI LATHE 110 V - eBay (item 370320808456 end time Jan-15-10 20:50:12 PST)
if you are just looking into making a heat sink the best way it to find the dia of the metal you want to get or make a drill press. (google it if you need to.) Buy a specialty bit the exact size you need it. you will not find the bit you need at a store or at least i was unable to. pick up a set of taping tools
Harbor Freight Tools
if you want to find metal in lots of shapes and sizes look from a local metal store or go to
Online Metal Store | Small Quantity Metal Orders | Metal Cutting, Sales & Shipping | Buy Steel, Aluminum, Copper, Brass, Stainless | Metal Product Guides at OnlineMetals.com
if you can not make one go and find a machine shop in your local listing and ask them to make it for you. alot cheaper that building the whole rig.
Lastly sounds weird but high schools and some middle schools have metal lathes ask the school if you can use there equipment. or get the shop teachers email and tell him what you want to do.