When I started modifying my old Samurai I had a 3/8" chuck electric drill and that was about it.  The first must have was a 4.5" grinder.  This versatile tool can both cut and remove material using an assortment of discs.  My favorites are some .045 thick cut of wheels for cutting and either a 60 or 120 grit flapper wheel for material removal. The flapper wheels are much nicer to work with than the stone style wheels because they flex and give.  Lehigh Valley Abrasives has the best prices on these wheels that I have found.

One trick I employ to save time is to keep two grinders on hand and ready, one with a cut off disc and one with a flapper wheel.

Tube Cutting

Band saws are quieter and less messy but you can't argue with the speed of a chop saw.  Just make sure you have plenty of ear plugs!

Tube Marking

I used to just use a sharpie but the marks were prone to getting rubbed off and it was hard to make a uniform mark around the tubing.  I ended up picking up a larger tubing cutter from Home depot and lightly score my cut or bend start lines before working on the tube.  The really nice thing is the marks make for good reference points down the road so you may want to take the time and mark the center of any cross braces to mark the chassis centerline.

Tube Bender

I am using a JD2 model 3 tubing bender. I modified the bender to use a cheap air over oil hydraulic ram to do the work.  This modification was detailed here.   For dies I prefer to use the smallest bend radii available for space reasons.

General Cutting

There are all sorts of tabs and gusset you will need to make and a myriad of tools to accomplish the task.  I use the cut off disc in my grinder for small or thick stuff.  For sheet or tabs up to .50" thick I use a plasma cutter (which requires an air source).  A band saw is also handy and can take the place of a plasma cutter but it cannot do large sheets.  FWIW the plasma cutter also works great on thin aluminum, you just have to file down the edge afterwards to clean up the slag (I have found the faster you drag the less slag there is on the thin stuff). I cut my hood and all of the aluminum body panels on my buggy with my plasma cutter.

Welders

The next step is a welder.  I went with a 220v mig over a tig because it is hard if not impossible to get a tig torch in some areas of a chassis.  I also wanted speed which the mig has in spades.  I will eventually buy a tig but it would be used mostly for small aluminum parts like interior panels.

Measuring Tools

Obvious I know, but I keep a bunch of tape measures, angle finders and square on hand.  It seems like you can never have enough.  Sometimes with the angle finders the trick is to find a way to measure an oddball plane.  I have made tube clamps with a flat or used a sheet that spanned a bend in a tube to figure out some of the more common angles you find in a chassis. If possible a digital angle finder is even better since it takes the angle of view out of the equation.

A digital protractor is also handy to check angles between tubes and to confirm angles after using the tube bender.

Tube Notching

I bought two Harbor Freight tube notchers.  One is setup in my drill press as shown.  The more expensive versions out there are basically the same but with sturdier bases and actual bearings as opposed to bushings in the spindle holder.  For the price ($29 on sale) the HF notchers work pretty good after a little bracing and replacing the hardware on them with grade 8 stuff.

The other tube notcher is a floater and gets mounted to whatever can accommodate the big tube that won't fit on the drill press setup.  For the most part it stays attached to my tube bender frame.  There are also times where the floater gets attached to a tube on the chassis itself. For really difficult notches like where 3 tubes converge I usually resort to sketching the notch with a sharpie and grinding the pattern out with a flapper wheel.

It goes without saying the notchers use bi-metal hole saws.  I have found I can get a chassis's worth of notching out of a hole saw if I brush it with cutting oil as it is being used.  The second picture shows how to line up a new notch so it matches the first notch.

Chassis Jig

Having a big, heavy and moveable table would be the best thing, but if you don't have the room even a simple rolling platform like the one I use can save you a ton of time and make your project much more uniform by giving you well defined surfaces to measure from.

You can also temporarily clamp  things to the jig to help align parts. Here are the plans I used to build the simple jig shown above.  I built this out of some small scrap tubing, ideally some 2 x 4 x .120 wall steel tubing would work better if you want it to also serve as a weld jig. Another nice thing is keeping the chassis mobile so you can adjust the work area to suit the task at hand.

Bead Roller

You will eventually get to making body panels and a bead roller allows you to use thinner material but roll a bead into it to make it more rigid and also eliminate any oil canning.  Shown above is another Harbor Freight tool that with a little love can be quiet effective.  In this case I had to added the bracing around the main plate to keep it from flexing.  the right hand picture shows the business end, the HF roller comes with about 8 different dies making it a bargain after a little effort.

The above panel has the path I want to follow with the bead roller laid out onto it.  Afterwards you can see the center part is indented which makes the thin panel nice and rigid along with giving it a nice look.

Dimple Dies

Dimple dies are small two piece die that go into a standard size hole and when tightened or pressed together cause the edges of the hole to flare inward or outward. The above press is a home brew unit I came up with, the dies are hanging to the right.

Here are some panels where I used the dimple dies.  Again the goal is to be able to use really thin material yet make it rigid so it won't vibrate.

Misc Cool Stuff

I picked up these tube positions from Van Sant and they are worth their weight in gold.  I also tried out some of the Pipemaster contour gauges but didn't find them very useful.

One use I found for small tube scraps is to create a set with different notch angles.  These come in real handy when trying to figure out what angle to set the tube notcher as well as when mocking up stuff.