Currently, I have a 1-inch Bi-Metal Hole Saw that has never been used; some of the other sizes have been used.

The box says High Speed Steel Teeth among other things.

I also have an incremental set of Razor-Sharp Silver & Deming bits up to 1-inch size; two matching sets, in fact.

I first thought the Hole Saw; but, no matter what I am cutting, they never tend to make the most accurate hole and sometimes not even round.

My thoughts are the big drill bits might make the better, more accurate hole.

My intentions would be to approach final diameter incrementally.

But then, those big bits can grab; and, when they grab, they grab violently; hopefully, one wouldn't grab so violently as to tear the tank.

I intend to thoroughly Power-Wash the insides of the tank once the hole is made, so I am not overly concerned with whatever shavings and filings might be a part of the process.

If something were to get left inside the tank, I would prefer it be a big long drill shaving rather than grinder dust.

Nothing is going to get past the gauntlet of filters between tank and engine, so anything left behind is more cosmetic that something to actually lose sleep over.

I have no idea how thick the tank is; it is a factory Ford steel fuel tank.

So, what will it be; Hole Saw or Big Drill Bits or do I need to spend money and wait for something else ?

Excellent idea ! However, my step-drills only go up to 3/4-inch.

Maybe I need to procure one that goes past 1-inch.

It is amazing how they can drill through something that would have other ordinary bits grabbing and making big burr edges around the hole.

I have never checked the angles on them; I don't know how they do what they do.

The only draw-back I have found to step-drills is I can't figure a way for my Drill Doctor to sharpen them. 

Lenox step drill as shown here. Just a screen grab as Lowe's and the box stores sell the same thing:

https://www.diamondtoolstore.com/products/lenox-vari-bit%C2%AE-step-drill-bits?variant=43931409154222&utm_source=google&utm_medium=cpc&source_campaign=&keyword&gad_source=1&gclid=Cj0KCQjwvb-zBhCmARIsAAfUI2s5tGdLcELiiSnRFCO3ELXUlxq6p7v52umpfBstTXaU4-NakoZZBH8aAjzBEALw_wcB" rel="nofollow - https://www.diamondtoolstore.com/products/lenox-vari-bit%C2%AE-step-drill-bits?variant=43931409154222&utm_source=google&utm_medium=cpc&source_campaign=&keyword&gad_source=1&gclid=Cj0KCQjwvb-zBhCmARIsAAfUI2s5tGdLcELiiSnRFCO3ELXUlxq6p7v52umpfBstTXaU4-NakoZZBH8aAjzBEALw_wcB

I do a lot of sheet metal work and have a good selection of step drills  of good quality.  I have been using them for several years and most have never needed re-sharpening other than one or two have had a slight touch up on the initial penetrating tip. 

I would recommend one for your project.

Drill Doctors are every bit as wonderful as they bragged them up to be way back when they were "As Seen on TV" material.

My wife got me my first one, the 750, for Christmas years ago and it is still going strong today, hardly a day passes that it isn't used at least once.

I can't remember, but it seems like she paid something like $150 and that was way back when a hunnert-dollar bill was big as a saddle blanket.

We hit lots of swap meets and I hoard stuff up; I have a very sharp eye for things I need and can use.

Since she got me my Drill Doctor 750, I have picked up three more just like it, brand-new and still in a dust-covered box, the wire ties still on the cords and all the accessories still in the little bags, probably never plugged in the wall, for something like five bucks apiece; I never saw one for sale like that before she got me mine.

I am sure some relative got these as gifts for the swap meet guys who were selling them for next to nothing.

I just can't fathom a genuine American male never using his Drill Doctor and then selling it at some yard sale for men; it actually causes me to lose respect for such an individual.

I always grab these when I see them as a replacement stone would cost lots more; but, I have so far only ever used that first one that she got for me while these others lay in waiting for the day it either quits or needs a stone.

I guess when I finally get my big many-bayed shop that I have been wanting all my life, and can finally quit laying on big #5 Limestone rocks out in the sun and rain, I can distribute all these Drill Doctors at various drill sharpening stations throughout the shop so I won't have to quit what I am doing and get on the golf-cart and ride it to the other end of the building to sharpen my bit.

Mine does up to 3/4"; I guess that's where the "750" comes in; the "500" does up to 1/2"

Coke-in-MN wrote: ... use a knock out punch used for electrical conduct ...

I thought of that too but figured not everyone had one in their back pocket. I sometimes wish I still had access to those from my sawmill days, but I don't have enough use for them nowadays to justify spending any money.

curious.... what is the hole for ?

If you need a precise 1" HOLE, USE A 7/8" holesaw, then file to 1.00000"

The hole is for a bulk-head fitting.

You have a lot more confidence in the accuracy of my filing than I do and I have made hammers, sears, and triggers from raw stock.

By "ream it", I am assuming you are meaning with an actual purpose-made reamer.

That is a really good option that I hadn't thought of if I needed to sneak up on final size.