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nmo 3/8 hole mount

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I've used a good SHARP 3/8" "unibit" drill bit with no problems. Not sure why anyone would say not to. I've not had any problems.
 

crayon

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Sharp being the keyword. :) Else you mangle the sheetmetal if the bit grabs for whatever reason.
 

kb2vxa

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Hi Billy with the hole,

Never mind those amateurs with the hole saws, that's the best way to make a ragged hole and tear up any nearby material in the vehicle. Greeley and others make a whole line of chassis punches, 3/8" is the one you want. Simply select the correct size drill bit to pass the bolt, pass it through the pilot hole, reassemble the punch and tighten with a wrench. Out pops the cut-out and the result is a nice clean hole.

Guys, a hole saw is ideal for woodworking but we're dealing with metal here. If you want to cut a hole for a doorknob use a hole saw, otherwise use the proper tools for metalworking.
 

grem467

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So the proper tool from tessco ISNT the proper tool?

gee good to know that after drilling hundreds of vehicles with it.
 

rcvmo

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Sharp being the keyword. Else you mangle the sheetmetal if the bit grabs for whatever reason.

And write your name across the roof:):)
rcvmo
 

crayon

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kb2vxa said:
Never mind those amateurs with the hole saws, that's the best way to make a ragged hole and tear up any nearby material in the vehicle. Greeley and others make a whole line of chassis punches, 3/8" is the one you want. Simply select the correct size drill bit to pass the bolt, pass it through the pilot hole, reassemble the punch and tighten with a wrench. Out pops the cut-out and the result is a nice clean hole.

Guys, a hole saw is ideal for woodworking but we're dealing with metal here. If you want to cut a hole for a doorknob use a hole saw, otherwise use the proper tools for metalworking.
I have to hand it to you kb2vxa, you never cease to amaze me with the sheer volume of useless mis-information that you can post. :)

a) The correct spealing of the hole punch company name is Greenlee.

b) One cannot BUY a 3/8" punch. However, you can buy a METAL hole saw just for making 3/8" nmo holes. How about that ...
 
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prcguy

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Like others have said, use a sharp drill bit and start with a smaller pilot hole, 1/8” is good and stepping to ¼” and then 3/8” is safer if you’re an NMO virgin. Find a thin piece of sheet metal or thin hard plastic to place between the headliner and roof to keep the drill bit from snagging anything, this way you won’t have to dismantle much in the roof. A hole saw is fine if you can find one that small. A Greenlee punch for this job is a bit silly as you have to DRILL a hole for it anyway and a Greenlee punch is more apt to damage your roof while swinging a wrench around trying to avoid scraping the paint or warping the thin roof material. You generally need a wrench on both sides, hard to do up inside a headliner and the punch will cost about $30. Also, 3/8” is an odd size for an NMO mount, they usually take a ¾” hole. The NMO was designed to be completely installed from the top of the roof by angling the partially assembled mount down into a ¾” hole, centering a lip in the below roof part into the hole, then screwing the top part down. They can be assembled into a 3/8” hole but they will not seat properly and can create a gap between the antenna and roof. Make sure the mfr calls out a 3/8” hole, otherwise get ready for a ¾” hole saw. I am still an amateur at this with only maybe 1000 vehicle installs done in a previous life. Hopefully some more experienced people will chime in.
prcguy
 

crayon

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prcguy said:
Also, 3/8” is an odd size for an NMO mount, they usually take a ¾” hole.
It is not an odd size, it is just not used as much as the .750 nmo since, by design, it is suppose to only be used in panels up to .128 in thickness.
prcguy said:
I am still an amateur at this with only maybe 1000 vehicle installs done in a previous life. Hopefully some more experienced people will chime in.
Either your an amateur or you are not! :) Be a man, call it like it is. Silly attempts a modesty is just that .. silly.

:)
 
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prcguy said:
Like others have said, use a sharp drill bit and start with a smaller pilot hole, 1/8” is good and stepping to ¼” and then 3/8” is safer if you’re an NMO virgin.
Thats why I mentioned the "unibit". It drills progressively larger holes and de-burrs at the same time. As with anything else, good technique, planning and common sense have to figure in this somewhere.
Also, 3/8” is an odd size for an NMO mount, they usually take a ¾” hole. The NMO was designed to be completely installed from the top of the roof by angling the partially assembled mount down into a ¾” hole, centering a lip in the below roof part into the hole, then screwing the top part down. They can be assembled into a 3/8” hole but they will not seat properly and can create a gap between the antenna and roof.
Actually, not true at all. Although the 3/4" is more common, there are 3/8" mouints readily available. As for a 3/8" mount not seating properly and creating a gap between the antenna and the roof, nothing could be further from the truth. I've used 3/8" nmo mounts for some time, and have never had a "gap" or leak or whatever. 3/8" mounts make sense if you can get to the underside of the roof (or wherever), don't want to drill a huge hole in the car, and/or don't do enough installations to justify the cost of a 3/4" drill bit or hole saw.
 
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