What Die Grinder bit to use? Need to enlarge antenna hole in fender

[4mulas]

Hi there, don’t do much metal or body work so looking for what recommendations folks have for die grinder bits to enlarge my antenna hole. It was radio delete car that the previous owner put a radio in and aftermarket antenna. The hole is not what factory mopar antenna uses so I’m changing the antenna to stock and getting rid of the crappy aftermarket one.

fortunately the hole the made is near the stock location, I just have to enlarge it to fit the new antenna.

I can only think of using a die grinder or dremel like tool for this and would like recommendations on a good bit to use that maybe won’t create too much heat. I have both the die grinder and dremel.

‘’thanks!

 

[Professor Fate]

I wouldn't even bother with a die grinder- just use about a 1" sanding drum on a drill- the slower speed creates less heat and is less likely to get away from you.

 

[dadsbee]

Greenlee unibit / step cutter. Hit up one of your electrician friends.

 

[6PakBee]

Black Oxide Step Drill Bit Set, 2 Piece

Amazing deals on this 2Pc Oxide Step Drill Bit at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

This.

 

[cudascott]

Tape over the hole and top fender surface with a couple layers of 3m painters tape and use your template and mark it out with a fine tip sharpie.
next use a sanding mandrel to enlarge the hole then use a small carbide bur for the two small open slots. Be careful with the carbide bur when you get them in tight spots they have a tendency to grab the other side of the hole or slot and get uncontrollable. I did this very job on a 68 barracuda fender to allow a 67’ antenna to fit.

 

[Jim Lusk]

The above answers make sense, but I went a completely different direction on my Barracuda. I filled the hole and bought an amplified "hidden" antenna. Similar to this one.

RetroSound HPA-1 antenna

 

[4mulas]

The above answers make sense, but I went a completely different direction on my Barracuda. I filled the hole and bought an amplified "hidden" antenna. Similar to this one.

RetroSound HPA-1 antenna

I would have preferred they left it alone as a radio delete car as well.

After all these and the Big Brother website FABO replies, I think I’m going to use a 1/4-3/8 ish carbide burr and take light passes with it until the desired hole size is formed. I will drill the two small locating slots first with a drill bit. I will decide which size burr to use once I can see them and hold them in hot little hands. The Larger 3/8 diameter is probably going to win that decision.

All of this after taping many layers and etching a fine line in the paint with a sharp edge to prevent chipping beyond the cut of the carbide burr.
‘’thanks for replies all

 

[Dicer]

As mentioned before post 2, use a sanding drum or stone in a dremel or similar tool. A burr or a bit may catch and pop out on you and it takes off way too material too quickly.

 

[Steve welder]

I would not use a carbide bit in a die grinder on sheetmetal. I strongly advise against doing that
Using painters tape, mask all around the opening, a good quality step drill ( Not a HF or cheap import) would work but be careful as you could easily make the hole to big, go slow, use care

 

[kiwigtx]

If you decide to use a Unibit to enlarge the hole, don't forget to ream the underneath.....even a Unibit will leave a jagged edge.

 

[Professor Fate]

Since, by your picture; the existing hole is off center from where you want the new larger hole, I would not use a Unibit or step drill. It will self-center on the existing hole and all you will end up with is a bigger hole in the wrong place. Tape it, mark it, and use the sanding drum. Put the hole where you want it, not where the drill wants to put it.

 

[TF360]

Hole saw the correct size vey carefully

 

[4mulas]

I ended up using a double cut carbide burr 1/4” x 3/4. Worked like a charm with light gradual passes. I etched the paint first to creat a sharp edge to prevent excess chipping etc…
the metal stayed nice and cool. I think a stone/drum sander would have taken a long time and created a lot of heat. Made a little bed of tape, sticky side up, to catch chips and filings from going into the bottom of the fender.