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Author Topic: Cleanest hole?  (Read 3412 times)
K5LXP
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« Reply #15 on: April 18, 2012, 09:20:39 PM »

In a warm, dry climate such as yours, I don't doubt that you've seen minimal corrosion damage.

Why do you think I moved here?   Smiley  Cars may not rust, but the heat and UV is hell on interiors though.


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leaving the paint on the outside edge of the new hole does--gives more protection.

Sure.   But I've never seen a hole saw remove the paint beyond the o-ring.


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Spend any length of time in New England, and you'll know what I mean.

My prime motivation for moving here - grew up in WI, then ME and MA for a decade.


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that o-ring insulated the mount from the roof metal--unless it is overtightened.

I don't see how you could tighten one without contacting the roof.  The point of removing the paint is so you didn't have to rely on the underside teeth because you wouldn't normally be able to, or want to gain access there to scrape the paint.  If you have endless time to painstakingly massage the process you can make just about any method work.  With a hole saw, poke the hole, run the line, tighten the ring and get on with your life. 

I can't say how many NMO's I've done this way but it's certainly many hundreds, possibly thousands.  My pickup truck I put its' first NMO in around 1986 back when I lived in Maine is still working perfectly, leak and corrosion free to this day (I've added 5 more to it over the years).   The last thing you want when doing this professionally is to have an installation come back because it's not working right, especially when it was your technique or error that causes it.  You don't have the time, nor can risk damaging a headliner or trim pieces dorking around with a punch or scraping paint.  Especially since you don't have to if you use the tool made for the purpose.

NMO's have stood the test of time because they don't leak, don't cause corrosion and can be installed without access to the back surface.  If it required extraordinary measures to install or maintain integrity, they wouldn't have been as widely adopted as they have.  The mount and tool to go with it makes this an easy and simple process.  Why make it any harder for one's self?


Mark K5LXP
Albuquerque, NM
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K7RBW
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« Reply #16 on: April 18, 2012, 10:10:18 PM »

I haven't done 100s or 1000s but the 1 I just did was about as easy as you could imagine. If it wasn't for all the airbags I could have installed it in less than 30 minutes. Even with the airbags and being my first time, it only took an hour or so. I can see how you could get a leaky one if the mount doesn't seat just right. But installed correctly, it should be air and watertight.
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K1CJS
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« Reply #17 on: April 19, 2012, 04:18:14 AM »

I'm not going to argue with a so called 'expert', Mark, except to say that that expert isn't following the installation instructions and is trying to convince others that not doing so is better.  Of the dozens of NMO mounts that I've put in, I've never squashed the outer o-ring down to the point of just about digging the threaded-on locking ring into the metal as you say you've done, and the ones that I've put in are still watertight and corrosion free.

If you find that you had to move to where you are to prevent the corrosion from starting, I can see why.  73 to you, since this will be my last post on this subject.
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K3GM
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« Reply #18 on: April 19, 2012, 04:26:36 AM »

Whether sawn or punched, I believe we can agree on the NMO mount as being probably the best permanent mounting scheme available today.  That said, a second hole goes into the trunk of my 2012 Fusion very shortly ....a punched hole! 8-)
« Last Edit: April 19, 2012, 07:54:26 AM by K3GM » Logged
AA4HA
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« Reply #19 on: April 19, 2012, 12:56:55 PM »

I worked at a company that made industrial control panels and some of those panel fronts had 20-30 holes for switches or lights. Almost everything was done with Greenlee punches.

One of the tricks they used as to not mar up the paint on the front of the cabinet was to put down a layer of masking tape before using the punch. It kept the punch from taking paint off the front of the cabinet.

Also, there are a few different type of Greenlee punches. I preferred the series called "slugbuster" that instead of removing just a wavery doughnut of metal it chopped out two crescent moon shapes. Some of the cabinets we did were in stainless steel and normal Greenlee punches would only be good for a few dozen operations before they became too dull when working on stainless. The slugbusters always held up better.

I would not use a Greenlee on fiberglass. Sometimes we had cabinets that were plastic or fiberglass. You ran a real high risk of cracking the cabinet with a punch. We would use a step-drill to do those.

If you are doing this only a few times and do not want to spend $25-$50 for a die then get a step drill. It works great for installing bulkhead mounted lightning protectors in boxes as well.

I have had a few "hole saw" disasters and do not recommend those.

One thing that is always problematic was in knocking holes that had a keyway (some buttons had keyway cuts). Thank goodness antennas do not do that.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
K5LXP
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« Reply #20 on: April 19, 2012, 09:13:43 PM »

isn't following the installation instructions

Per the Motorola mobile installation instructions included with most radios, back when they came with printed manuals:

"Use a Motorola hole cutting saw (Model ST-157) or equivalent.  When this type of saw bottoms on the roof, it cleans off the paint in a neat circle around the hole and assures a good electrical contact with the locking nut."

"Tighten the locking nut until it bottoms firmly against the rooftop.  The locking nut must come in contact with the bare metal of the car roof to insure electrical contact.  The rubber o-ring is fully compressed when the locking nut is tightened."

I'd be happy to scan the instruction sheet for anyone interested.


Mark K5LXP
Albuquerque, NM

« Last Edit: April 20, 2012, 08:37:07 AM by K5LXP » Logged
AD7GU
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« Reply #21 on: April 22, 2012, 06:23:07 PM »

worked for a motorola dealer for years, we used the motorola/antennex hole saw.
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N6AJR
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« Reply #22 on: April 23, 2012, 11:00:48 AM »

another install trick with a hole saw is to start it or even run it all the way in in reverse direction.  sometimes in the normal "forward" mode the saw will catch and rip metal, especially in the very soft metal of some newer cars. running in reverse stops the ripping of the metal. take your time and work slowly and with care. 
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