Hole size for NMO ant mount?
WB7ASR
What tool would best be used to make the hole?
WB7ASR...
Bob KB9MS
a hole saw but you tend to put too much pressure downward and wrinkly the roof.
First make a pilot hole bigh enought for the chassis punch screw, then under
the hole scrape a little of the metal so there is a good ground connection.
Best antenna mount Ive ever used. Good Luck..
73 de Bob KB9MS Raleigh
--
******************************************************************************
Bob Lukaszewski KB9MS Replies to Internet 'rlu...@bnr.ca' or 'kb...@nando.net'
The views expressed here do not reflect the opinions of BNR or Nortel..
Bob Wilson
>
> What is the hole size is required for the Larson NMO antenna mount?
> What tool would best be used to make the hole?
>
> WB7ASR...
Tom,
A 3/4" hole is the typical requirement...although other "special"
bases are available...such as 3/8".
A 3/4" hole saw on an electric drill has worked just fine for the
dozen or so I've installed. You just have to be mindful of the
headliner!
Good Luck
Bob Wilson
WA4PUJ
John Bradley/KK5MH
>What is the hole size is required for the Larson NMO antenna mount?
>What tool would best be used to make the hole?
>WB7ASR...
I used a 3/4" hole saw with a built-in pilot drill. The instructions
are included with the NMO mount. I recommend using a high quality saw
to avoid messing up the car.
73,
John
Doug Faunt N6TQS +1-510-655-8604
From: Bob Wilson <wa4...@ix.netcom.com>
Newsgroups: rec.radio.amateur.antenna
Date: Wed, 14 Feb 1996 20:14:59 -0800
WB7ASR wrote:
>
> What is the hole size is required for the Larson NMO antenna mount?
> What tool would best be used to make the hole?
>
> WB7ASR...
Tom,
A 3/4" hole is the typical requirement...although other "special"
bases are available...such as 3/8".
A 3/4" hole saw on an electric drill has worked just fine for the
dozen or so I've installed. You just have to be mindful of the
headliner!
Good Luck
Bob Wilson
WA4PUJ
I'd also suggest covering the area near the hole with tape. The hot
metal chips from the sawing can melt their way into the clearcoat and
be unremovable. They then rust, and make a mess.
73, doug
Jeff Stillinger
In article <3122B3...@ix.netcom.com>, Bob Wilson (wa4...@ix.netcom.com) writes:
>WB7ASR wrote:
>>
>> What is the hole size is required for the Larson NMO antenna mount?
>> What tool would best be used to make the hole?
>>
>> WB7ASR...
>
>Tom,
> A 3/4" hole is the typical requirement...although other "special"
>bases are available...such as 3/8".
>
> A 3/4" hole saw on an electric drill has worked just fine for the
>dozen or so I've installed. You just have to be mindful of the
>headliner!
>
>Good Luck
>
>Bob Wilson
>WA4PUJ
>
Remove the headliner when doing the install. I have also found that
the 3/8" hole and mounts are much easier to install.
--
Jeff Stillinger <j...@ibbs.av.org>
David R. Mohr
writes:
>
>WB7ASR wrote:
>>
>> What is the hole size is required for the Larson NMO antenna mount?
>> What tool would best be used to make the hole?
>>
>> WB7ASR...
>
>Tom,
> A 3/4" hole is the typical requirement...although other "special"
>bases are available...such as 3/8".
>
> A 3/4" hole saw on an electric drill has worked just fine for the
>dozen or so I've installed. You just have to be mindful of the
>headliner!
>
>Good Luck
>
>Bob Wilson
>WA4PUJ
A 3/4" Greenlee Chassis punch works well also.
Dave O'Neal
>
>tom_...@ccm.ch.intel.com (WB7ASR) wrote:
>
>>What is the hole size is required for the Larson NMO antenna mount?
>>What tool would best be used to make the hole?
larsen). This will keep you from dropping the bit into the head-
liner. Also, before you drill, LOOK UNDERNEATH! Usual access is
via dome lamp. Make sure that you are not drilling on top of a
support beam. Make sure that the head liner and wires are out of
the way. Make sure there is a path for your coax... some cabs
have a double metal roof or other obstacles. Remember that the
hole is PERMANENT... make sure it's where you want it.
good luck
Rod Dinkins
it will buckle the sheet metal -- I know I did it,\.%#@*&% not bad tho Hi
Hi
Using these mounts gets a nice ground plane for the antenna. I use a 1/4
wave around town (low garage door) and a 5/8 while travelling.
Good sawing
Rod
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Jim Chandler
Rod Dinkins <ac...@ix.netcom.com> wrote:
>I agree with the hole saw comment. DO NOT USE A PUNCH such as Greenlee
>it will buckle the sheet metal -- I know I did it,\.%#@*&% not bad tho
>
Greenlee punches work great, but to keep from it from buckling the sheet
metal, tighten slowly.
Jim Chandler, N0VAH
j...@a.crl.com
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Mark Herson, N2MH
>tom_...@ccm.ch.intel.com (WB7ASR) wrote:
>
>>What is the hole size is required for the Larson NMO antenna mount?
>
>
>I used a 3/4" hole saw with a built-in pilot drill. The instructions
>are included with the NMO mount. I recommend using a high quality saw
>to avoid messing up the car.
>
>73,
>John
>
An even better suggestion is a 3/4" Greenlee hole punch. Makes really
nice clean holes for NMO mounts.
73, Mark
Chris Boone
> From: Gary Thorburn <gtho...@xyplex.com>
> Subject: Re: Hole size for NMO ant mount?
> Organization: Xyplex, Inc. Littleton, Massachusetts
>
> John Bradley/KK5MH wrote:
> >
> > tom_...@ccm.ch.intel.com (WB7ASR) wrote:
> >
> > >What is the hole size is required for the Larson NMO antenna mount?
> > >What tool would best be used to make the hole?
> >
> > >WB7ASR...
> >
> > I used a 3/4" hole saw with a built-in pilot drill. The instructions
> > are included with the NMO mount. I recommend using a high quality
> saw
> > to avoid messing up the car.
> >
> > 73,
> > John
>
> just drill a pilot hole first. However, the "punch" only works
> if you have access to both sides of the metal you are cutting
> thru, for example if you can drop the dome lite and access
I disagree! as one who has been doing antenna installs for 20 years, I found
the BEST tool for a NMO mount install is a 3/4 in counterBORE bit (NOT
counterSINK)...
You drill a small 1/4 pilot and then insert the counterbore bit in the
hole...it has a smooth pilot that does not wobble or open the hole up..
and it SHAVE the 3/4 in hole open....no jagged edges......NO need to get
underneath....just make sure you have clearance where the NMO mount is
going...and do NOT force the 1/4in drill bit too deep when drilling the pilot
hole...
a PUNCH will distort the metal around the hole.....and the mount may never
seat correctly....causing water leaks etc....
73
Chris
--
|Fidonet: Chris Boone 1:106/4267
|Internet: Chris...@f4267.n106.z1.fidonet.org
|
| Standard disclaimer: The views of this user are strictly his own.
Gary Coffman
>I agree with the hole saw comment. DO NOT USE A PUNCH such as Greenlee
>Hi
A Greenlee punch will make a beautiful hole, if the punch is sharp.
If it isn't, why not? Stone it. A ratty old hole saw can make a hell
of a mess of your roof too. Take care of your tools and they'll take
care of you.
Today's cars use very thin high strength steel construction, a backer
plate is usually a good idea whether you saw or punch. And leave the
backer in place when you mount the antenna. That'll help keep it from
pulling out if you hit something with the antenna.
Gary
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John Gianotti
hole for an NMO antenna mount is with a genuine Motorola hole saw. This
nifty device combines a hole saw with a colar that prevents you from
going through the headliner of the car when the saw punches through. Get
on from a Motorola Service Center (but be prepared to pay). Best idea is
get your club to buy one they can loan to members.
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Richard G. Slavens
one and be prepared for a easy installation. It will also scrape away a
small ring of paint for a good antenna ground connection.
You might be able to borrow/rent one from a local Commercial Radio shop.
73,
Dick WA6TMF
----------------------------------------------------------------------
Woodybozak
automobile, I've found the 3/4" holesaw (with 1/4" pilot bit attached) the
BEST choice. However, if you want to use what Larsen recommends, they
sell (or used to sell) their own 3/4" saw that also removed a 1/16" area
of paint beyond the hole to provide a good ground connection for the brass
nut/vehicle body. I've never been tempted to use a chassis punch, as it's
rare to have enough assess to the area below the hole (as stated in
another response).
Jeff DePolo WN3A
Wouldn't using a hole saw that produces a 1/16" ring of bare metal need to be
used from the inside of the car? NMO mounts make no electrical connection to
the vehicle body on the outside - there is an O-ring in the brass nut that
contacts the outside of the vehicle, but that's it. The grounding is supposed
to be done on the inside - that's why the edges of the inside-half of the
mount are serrated to dig into the metal for grounding (in addition to keeping
the mount from spinning).
I've probably done 30 or 40 hole mounts, admittedly not as many as some of the
guys that do it for a living, but I haven't had problems with the chassis
punch with respect to deformation of the metal, but maybe I've been lucky. I
do use cutting oil - maybe others that have used chassis punches with bad
results didn't? Yes, getting access is a bit more difficult, but it produces
a hole that is not "torn up" on the outside if you put the wrench-side of the
chassis punch inside the car and the cutting side of the punch on the outside.
I had a hell of a time trying to use the chassis punch on my Chevy Tahoe - it
has a double-roof with some "holes" in the inner roof where I was able to get
access.
And as someone else mentioned, MAKE SURE YOU TAKE PRECAUTIONARY MEASURES TO
KEEP THE FILINGS FROM DAMAGING THE PAINT WHEN YOU DRILL THE PILOT HOLE! On
some paint types, the hot filings will melt the coating and embed themselves
in the paint, and they soon rust and make a real mess. Again here, cutting
oil (or other light oil that won't harm the paint) is your friend - a small
puddle of it around the hole area will cool the filings as they fly off the
bit before then can do any damage. Pick up as much of the oil/filings as you
can with a paper towel by blotting. A paper towel wrapped around a mag-mount
base is another good way of getting the filings off the roof without wiping.
I suggest washing the roof at one of those high-pressure self-serve carwashes
afterwards to make sure you got all of the filings off the roof.
The hole saw that Larsen makes no longer appears to be a hole saw in the
traditional sense - it looks more like a Unibit in the catalog I have, and
sells for $13. Has anyone used a Unibit for this purpose?
A company called Ripley makes traditional antenna hole saws that limit the
depth to 1/8"; they may OEM the Motorola hole saws.
--- Jeff
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-Jeff DePolo WN3A Twisted Pair: H:610-337-7383 W:215-387-3059 x300
dep...@eniac.seas.upenn.edu RF: 442.1 442.2 442.4 443.45 443.8 444.15 linked
Claim to Fame: I got the 1st speeding ticket on the information superhighway
Gary Coffman
>
>a PUNCH will distort the metal around the hole.....and the mount may never
>seat correctly....causing water leaks etc....
A *dull* punch with a sloppy fit into its die may distort the
metal. A sharp punch in a well fitting die will produce a cleanly
sheared hole. Better than a hole produced with the average drill.
Woodybozak
o-ring flattens out when compressed. Thus, the brass nut does indeed make
a good electrical connection to the vehicle, from the OUTSIDE, if the
1/16" ring of paint/primer is removed by use of the proper hole saw (or
carefully removed by some other means). The teeth of the underside mount
are, as you indicated, required to keep the mount from spinning when the
brass nut is tightened. However, when Motorola engineers developed the NMO
mounting system, they recognized that the underside of automobile roofs,
fenders, trunk lids, etc., are often corroded, coated with oils and other
compounds from the die-stamping process at the factory, so they needed a
way to ensure positive electrical connection would be possible from the
OUTSIDE of the vehicle. The o-ring will not only compress and facilitate
an electrical connection, but the o-ring also will protect the grounding
area (now bare paint) from rust, etc., as the o-ring is on the outside of
the grounding area! Good job, Motorola. As a side note, the 3/8" NLA
mount can be used with NMO antennas by use of an NLA/NMO adapter ring (if
they're still available).
Ginsberg Family
>John Bradley/KK5MH wrote:
>>
>> tom_...@ccm.ch.intel.com (WB7ASR) wrote:
>>
>> >What is the hole size is required for the Larson NMO antenna mount?
>> >What tool would best be used to make the hole?
>>
>> >WB7ASR...
>>
>> I used a 3/4" hole saw with a built-in pilot drill. The instructions
>> are included with the NMO mount. I recommend using a high quality saw
>> to avoid messing up the car.
>>
>> 73,
>> John
>
>Best tool is a "Greelee Punch", 3/4-inch size. Nice, Neat job, you
>just drill a pilot hole first. However, the "punch" only works
>if you have access to both sides of the metal you are cutting
>thru, for example if you can drop the dome lite and access
>
>/****
>* Gary W. Thorburn KD1TE
>* email address: gtho...@xyplex.com
>****/
If you have acces to top and bottom you need not drill a 3/4 inch hole
there are NMO fittings that I purchased that only require a 3/8 hole, I
used one and they work fine. I purchased mine at the Queen Mary
convention but there are other source I am sure if you check around. A
3/8 inch hole can be done with not much more effort then the pilot for
larger 3/4 inch NMO Hope that helps. Ed Ginsberg KE6BNL
Bruce Burke
}
}a PUNCH will distort the metal around the hole.....and the mount may never
}seat correctly....causing water leaks etc....
}
}Chris
}--
}|Fidonet: Chris Boone 1:106/4267
}|Internet: Chris...@f4267.n106.z1.fidonet.org
}|
}| Standard disclaimer: The views of this user are strictly his own.
}
That is incorrect. The design of the punch prevents this as the
metal is supported around the outside perimeter of the hole being punched.
Actually, if it didn't, you wouldn't have a punch.
If the metal becomes distorted, it is because the user of the punch has placed
a lateral force on it deflecting the punch from a perpendicular position
to the metal being punched.
If the punch is damaged or worn out, that too could warp the metal being punched.
Like any other tool, it must be in good shape.
Greenlee punches are especially nice because they have a beveled punch. This
design makes it act more like a shear than a punch, ensuring the metal isn't
stretched by the punching action.
73,
Bruce
PTracy
(Woodybozak) writes:
> However, if you want to use what Larsen recommends, they
>sell (or used to sell) their own 3/4" saw that also removed a 1/16" area
>of paint beyond the hole to provide a good ground connection for the
brass
>nut/vehicle body.
Yes, I believe they still do. I borrowed on from a buddy of mine. The
Larsen hole saw did a real nice job, much better than the typical Lennox /
hardware store variety. As I recall the "blade" had a much finer pitch
than the typical hole saw.
mlmitchell
MOTOROLA also makes and sells a similar unit for the 3/4" hole for
the NMO mount, which, by the way, was a Motorola original, long before
Larsen thought of it .