Can i use a normal drill and a doorknob hole cutter on it to make a hole about the side of a doorknob in my hood? Any thing i need to do it so i dont screw up my hood.

 

First a question... why you drilling a hole in your hood?? Second, i would suggest putting masking tape over the area to be cut beforehand. This should prevent marring the paint in case the drill runs out. I'm pretty sure there's another reason, but i can't think of it right now. Hope this helps.

 

Im installing a hood tach on my car. Im not concernd about the paint becasue the car is in 10 different colors.

 

sounds like a nice clean way to blow a hole in your hood

 

Ok cool. This should be fun and a learning experience.

 

you mask where you cut to prevent tearing the metal, i would mask both sides. You'll sand it after the cut but you'll save some time on sanding if you mask.

 

so basicly mask the whole area im going to cut. mark the spot im gonna drill on the masking tape. and have at it.

 

A piece of masking tape is not going to do jack against a hole saw. It won't hurt anything but, that's your call.

There aren't tons of options with hole saw blades (as far as TPI options) but, a few things to do to help avoid a problem.
Start with getting a Bi-Metal hole saw. The hole saws for residential (wood) doors (like the black Vermont American saws) won't last long on metal. Lowe's sells Lennox blade/mandrel combos for $14 or less depending on the hole saw size.
Drill a pilot hole, don't try to just power through with the mandrel's drillbit.
If possible, use a drill with a clutch and a low speed/high torque trans (like a DeWalt). This will help prevent the blade from 'grabbing' the metal once you get through the pilot hole (which can cause a nasty problem). A small amount of WD40 doesn't hurt but, really doesn't do much more than smell bad once the blade starts cutting. The slow speed will help from building too much heat that could potentially warp the surrounding metal.
Moderate pressure is all that's needed. Shouldn't take more than 30 seconds.
Just my opinion though...

 

I was going to drill my pilot hole with a dremmel if only i could do the whole job with my dremmel that would be awsome. But it will come in handy to smooth down the edges.

 

yeah masking tape won't do to much, ive never tried it but since you don't car to much about your paint maybe duct tape might perform better at keeping the cuts clean, and of course drill a pilot whole and use a metal cutting blade. WD-40 is a great tip and would definity recoment spraying the blade every so often. Don't use to much force is a the big thing here, let the blade do the work /if you muscle the cut the blade will grab and if your not ready for it the drill will fly from your hands and/or destroy your plans for a perfect hole.

/best of luck

 

One other thing before my brain stops talking to me for the evening... buy the next (1/8" if poss.) size smaller holesaw from what you want. No matter how steady you want to be, the saw will 'walk' a little making a hole larger then you want after you clean the cut edges.

It's much easier to cut small and remove extra to get your size than to cut large and fill back in when dealing w/metal.