These are the recesses for the nuts that secure the studs for the tail light assemblies. The holes were bondo'd over and then cut as you see in the photo below. What sort of tool cuts bondo in such a way? The holes on the other side of the car is still flat with bondo and need to be cut in a similar manner.
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Holesaw
It’s a very smooth cut for a hole saw. Maybe not all hole saws are created equal?
Maybe a Blair Rotabroach . They do nice holes in sheet metal compared to a hole saw
I used that and it worked
Most body fillers will work much like wood does. I would say that a wood Forstner bit will give you a finished hole that resembles those. It likely would need a pilot hole to center it though.
The hole on the right cannot be cut with a regular drill and hole cutter. It will need to be a close quarters drill and a short bit.
This is called a counterbore. Try WLFuller.com. Order it without spurs 0and with an I.D. to match the nominal diameter of your hole. Use a bit of straight rod or a drill bit chucked into the drill motor upside down as the mandrel. WL Fuller is a GREAT resource, as is McMaster-Carr.
Home Depot Carries several 90 degree “close’ adaptors for your drill. We use a Dewalt product. If you haven’t applied the filler yet, get a socket of the desired O.D., wrap one turn of 3M clear packing tape around it to serve as a release agent, bolt it in place, and putty away!
Ed's 'counterbore', or a piloted spot-weld cutter. They come in graduated sizes
I'd be asking a different question; why is there so much bondo and on both sides of the light housing, mine are flat sheet metal!
That's the way the project came to me. The engine bay was being smoothed by Kirk Evans at the request of the prior owner and it looks like that's the way he does it. The bondo might be thinner on the passenger side and I will find out shortly.
you can ask Kirk What he uses..
A hole saw. You need something with a centering bit. Those wood working bits will wobble and ruin the cut as you have no centering surface. They make a diamond coated hole saw bit that people use to cut plexi. I assume this will all be covered or not relevant when done. If you have no centering hole it will be a crap shoot. Even a regular blade hole saw if used correctly cuts a very nice sharp hole. I use the regular blades on very thin obechi ply on sailplane wings with no issue.
Here is what I ended up using. It produced cutouts that the same as Kirk's. I started with a 1 1/4 spade bit to start the circle. I drilled a pilot hole from the rear of the car. After the circle was cut I ground off the horns on the space bit allowing it to bottom out in the hole. I had to shorten the bit to make clearance with fender when cutting the hole towards the outside of the car.
Cool. What is the angle drive?
@panterapatt posted:Cool. What is the angle drive?
It is Harbor Freight's for about $16 on sale. I needed one with a chuck since the shortened spade bit shaft is round.
