Broken drill bits

Try using this. I stopped breaking them after using it. Just make sure you wash the off of body when finished Forney 20857 Tap Magic Industrial Pro Cutting Fluid, 4 oz www.amazon.com/dp/B003X3ZKXI/ref=cm_sw_r_cp_api_i_Z9FWQTYPHJH502F95QZA?_encoding=UTF8&psc=1

Usually when I've snapped a bit it's cause the casting has tipped as i'm drilling or I'm too impatient and forcing the bit. 

I haven't drilled any car rivets yet but over  decades of model railroading I've drilled a lot of holes in soft metals including brass and white metal rivets..

Make sure bit is sharp and work piece is held securely. Use relatively light pressure, as in let the bit do the work. Don't force it. 

I really like bee's wax as a lubricant on small drill bits and taps. It is also less of a potential mess than liquids. Just rub a little on the bit. Friction will melt it. I keep a small chunk on my hobby bench. Great lube for razor or jewelers saw too.

If you need another option for a comercial liquid, I used Rapid Tap throughout my industrial maintenence career. 

Good luck. Let us know how you make out.

I'm snapping them left and right. Most of it is my impatience but some are just snapping off only a few mm in the post. The tough part is when they snap off and the tip remains in the post. I'm finding the bits get dull really fast. I thought the castings were made of aluminum and magnesium. I feel like I'm trying to drill through unobtainium.

I have drilled/tapped for decades

First good bits is a must:

www.amazon.com/Gyros-SpeedSteel-Storage-Screwdrivers-45-21251/dp/B001WMMI8W?th=1

then, I use NO LUBE, 

lube grabs the chips and prevents them from falling out of the hole

for a full depth post hole I drill the hole 1/2 doxen times, going 1/8-1/4" deep max,

then clear the chips.  

so the sequence goes like this:

drill front, (1/8" deep), clean chips, drill rear post, clean chips
return to the front drill 1/8", clean, move to rear post
(a long chip will bind in the hole, keep the chips short/tiny)

keep alternating, allowing the diecast to cool off between drilling

to tap, use a long tapper tap to start,  1/4 turn in, 1/2 turn out,
clear chips (use drill in a pin vice) now do the other post same way,
return to the first, 1/4 in 1/2 out, slowly getting deeper.  When the tap bottoms, change to bottoming tap, same technique.  Finish with a re-dressed blunt, broken tap to dress the hole

If you are breaking bits it is either dull bits, pushing too hard, or removing too much material in one pull

If you have sharp bits, you do not have to push hard.

One other thing of note is to push the drill bit as far into the drill motor as possible... exposing just a little more than needed to get the job done...

and another note on the whole drilling/tapping thing... I no longer tap the hole. I use a little larger drill bit and then use the screw to self tap the hole... works way better for me... also, I find myself drilling less and less as I use E6000 adhesive to glue the weights in and the chassis to the body. Still removeable but quite strong. Comes in black, white or clear... not sure if the white or clear is a different formula as I only use the black myself...