Drilling The Holes...Which Direction?

[CanesFan95]

Here's a couple shots of the scrap.

 

[CanesFan95]

Then I did a second hole in the middle as another test.

 

[mmckenna]

Looks like a round hole to me. Try the NMO mount and see how it does. I'm betting it's going to be just fine.

Try using less pressure. It's hard to tell exactly how thin that material is, but there seems to be some slight deformation around the edge. That's usually from too much pressure. In reality, that'll be hidden by the antenna.

 

[CanesFan95]

And finally, here's a few shots with the mount installed in the first hole in the corner.

 

[CanesFan95]

While I do appreciate everyone's input about what drill bit to use, the DeWalt performed like a champ. It was actually very smooth and did not wobble or walk at all. The cut was quick and felt as easy as butter. Seriously.

It does tend to punch through though, so I might not want to use this for a roof install. But for the trunk, it is going to work just fine. The NMO mount looks like there is some wiggle room in the diameter as though the hole was just a bit too wide. But those are very close-up shots and it's hard to hold it exactly in place with one hand while snapping the photo.

Regardless, the mount still attached firmly barehanded with no problem, without a wrench.

 

[prcguy]

Its not the right thing to use, its just a better thing to use for the installation professional. You cant compare it to using a connector crimper to pliers. It sounds like most of the negative comments are from people who have never installed an NMO or at best they put a total of one on their car and it took all day because they don't have the experience to back up these silly claims. I still think recommending an NMO saw is like telling someone they need a $500 hammer drill to make just one hole in concrete, when they already have a suitable regular drill.

If I remember right the NMO mount turned up around 1968 and the NMO hole saw is a much more recent invention. There must be tens of thousands if not more NMO mounts installed by professional installers before the NMO hole saw was ever invented. So are all the pro installers that used a regular hole saw because the NMO saw didn't exist a bunch of idiots?
prcguy

They're expensive because they are the RIGHT thing to use. It's the difference between using a hexagonal die crimp tool for RF connectors like Mini-UHF, N-type, etc, and using a pair of 2 dollar slip-joint pliers. Yes, the 2-dollar pliers will work, but not very well.

Ever try to slice raw meat with a table knife? FWOMPT

 

[mmckenna]

While I do appreciate everyone's input about what drill bit to use, the DeWalt performed like a champ. It was actually very smooth and did not wobble or walk at all. The cut was quick and felt as easy as butter. Seriously.

It does tend to punch through though, so I might not want to use this for a roof install. But for the trunk, it is going to work just fine. The NMO mount looks like there is some wiggle room in the diameter as though the hole was just a bit too wide. But those are very close-up shots and it's hard to hold it exactly in place with one hand while snapping the photo.

Regardless, the mount still attached firmly barehanded with no problem, without a wrench.

Looks good. If you are happy with it, that's all that matters. The mount installed correctly.

Let us know how the install on your trunk turns out.

Kudos to you for doing this. Most hobbyists are uncomfortable with the thought of drilling into a vehicle. Truth is, it will work better and it will look better. It's isn't hard to do once you have the knowledge.

Beware, though. Once you start doing permanent NMO mounts, you'll never go back.

 

[CanesFan95]

A little more to the story. I actually did an NMO install on the car a few years ago, and this is currently the same setup I have now (photos below). Back then, I used a "proper" antenna hole saw and it worked OK (I forget what brand), but I actually think the DeWalt bit felt smoother.

I later tried to use the "proper" hole saw for some pieces of steel sheet metal so I could put a few NMO antennas up in the apartment attic with a ground. The teeth on the "proper" hole saw quickly flattened out and was no match for the steel. I ended up going to a local sheet metal dealer and placed an order including them punching the holes.

The plan now is to add a second antenna to the car to add a scanner. So I'm going to plug the first one and drill 2 new holes on the trunk, one on the left and one on the right. This is what I should have done in the first place. And you're right about the NMO addiction. It looks so much better than a mag / lip mount.

 

[clbsquared]

I'll be the first naysayer to admit. That saw did a pretty good job. But remember, the trunk will be a little thicker than the baking sheet. But what you did looks good. Everyone has to start somewhere and I suppose a hardware store hole saw is better than what I used the first time. I was 16 years old and all I could find was a 1/2 inch drill bit. So that's what I used. Drew a circle with a magic marker and wallowed the hole out with the 1/2 inch bit. It wasn't pretty, but it worked. Good luck on your first true install.

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[clbsquared]

The NMO hole saw is not designed to cut through anything any thicker than an auto body panel. Anything thicker than that and you would need a unibit or a broach cutter( which has the ability to cut thru 1/2 thick mild steel. The thing about drilling into metal is to go slow. If you go to fast, you'll just flatten the teeth or point on any hole saw or bit. Speed builds up heat and heat weakens and dulls even the best saws and bits.

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[N4GIX]

The NMO hole saw is not designed to cut through anything any thicker than an auto body panel.

It would be nice if everyone would remember to DELETE the images when they quote a post...

 

[RFI-EMI-GUY]

Did the drill have that spring on it?

 

[clbsquared]

It would be nice if everyone would remember to DELETE the images when they quote a post...

Sorry. I fat fingered the reply option on my phone. It's fixed, sir.....

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[CanesFan95]

Yes, the DeWalt drill bit comes with the spring on it.

 

[jackj]

Back-in-the-day when I was doing 2-way radio installs, I used a 3/4" Greenleaf hole punch. Drill a 3/8" hole and insert the punch bolt then screw on the other half. Of course this requires access to both sides of the metal but it will produce neat, clean and exact size holes without paint scratches if you don't use a conduit punch.

 

[mmckenna]

Back-in-the-day when I was doing 2-way radio installs, I used a 3/4" Greenleaf hole punch. Drill a 3/8" hole and insert the punch bolt then screw on the other half. Of course this requires access to both sides of the metal but it will produce neat, clean and exact size holes without paint scratches if you don't use a conduit punch.

I've got one of those too. There are instances where they are a good option. I don't use mine very often, but when I do I'm glad I have it.

There doesn't need to be just one tool that works. Having options can be a good thing.

 

[ramal121]

Is it me or does that mount look a tad tall. It's not some kind of thick mount is it? Anyway, don't try to crank the antenna down to touch the car body. Just make it snug and if there is a gap, oh well. NMO's won't leak regardless. I've seen too many broken bases where some gorilla torqued them all the way down.

Also note all hole saws leave a burr on the underside. If you angle in a rat tail file and remove it your mount will center easier and tighten up without spinning. No need for needle nose/o-ring pliers.

Otherwise I see no problem for you.

 

[radioman2001]

I use a Ripley hole saw kit, its got fine thread and depth limiting blade which also clears away some of the paint for good grounding. That particular hole saw has been around since at least the 60's when it was listed in Mot's parts catalogue.

I don't know about other brands of car and trucks, but I have found Ford sheet metal very thin, almost on the order of a soda can. So you don't want to use too coarse a saw making holes as you could actually tear the panel. Also Ford and others I am sure like to hide modules all over the inside of their products, so pulling down the headliner or clearing behind wherever you are drilling is a must. For roof panels in sedans and crossover vehicles I use a paper cup positioned under where I am drilling to space the headliner away from the drill bit and catch all the filings. The new Explorer is a breeze since the whole headliner is held in with magnets. The whole thing just drops down in one shot. Getting back to the thin roof panel on the Explorer I ended up installing a 1900 box cover between the antenna mount and the roof panel to stiffen it up and prevent a tear out if I hit something like a garage door opening with the antenna.

When I worked for GE as a radio installer for NYSP and other agencies in the early 70's I used to use a Geenlee hole punch also. I actually still have that exact punch in my tool box. You should see the hole needed for the low band ball and spring antenna.

 

[RFI-EMI-GUY]

Yes, the DeWalt drill bit comes with the spring on it.

Can you remove it?

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[mmckenna]

Can you remove it?

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Yes, it just pulls off. Tried it with the hole saw I had at home. Pilot bit depth is adjustable, too.