hammer drills are used for concrete and masonry not steel if your drilling thick steel you should use some form of lubricant. Keeping the tempeture down on the bit and the steel is vital some steel actually gets harder the more heat you generate. I wouldn't waste your money on a hammer drill get a better 1/2" drill cordless are better as most drill bits are sharpened to work well with them

 

Your correct I just used my Dewalt 14V cordless this time and it drilled them out fine just be sure you have a spare battery or two on hand as the power drains out. I made sure I had new sharp carbide drill bits that helped me a lot I grabbed three new ones to do the job with never used the oil I was going to but never did.

One note my Drill did get rather Hot at the end those bottom rivets are hard very hard

 

Here is another thread on this that may help others

LINK

This one may be very helpful also

LINK