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   Home   Help Search  
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Author Topic: NMO hole size  (Read 12660 times)
KI4NPZ
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Posts: 4




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« on: January 20, 2008, 07:40:45 AM »

Going to install an NMO mount and need to know what size hole to drill.  Is a 3/4" or 13/16" hole that is required? I've read different things from different places.  
Thanks!

Craig
KI4NPZ
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K5PHW
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Posts: 106




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« Reply #1 on: January 20, 2008, 07:44:37 AM »

 3/4 will do just fine. Just take your time.



Clyde
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W3LK
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Posts: 5639




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« Reply #2 on: January 20, 2008, 08:36:42 AM »

Motorola's specifications call for a 3/4" hole. Some third-party (import) mounts and non-standard and require the slightly larger 13/16".

Only buy NMO mounts that are American made. The foreign mounts have other problems beside hole size. Buy only from Motorola, Larsen, Max-rad and Antennex.

The best thing to use is ether a 3/4' chassis punch or the hole saw from Antennex. Do NOT try to use a 3/4" drill. You will mangle the sheet metal.

73,

Lon - W3LK
Naugatuck, Connecticut
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KB1LKR
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Posts: 1897




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« Reply #3 on: January 20, 2008, 11:09:40 AM »

Be sure that's a 0.750" (3/4") chassis punch, not a chassis punch for a "knock-out" hole for a 3/4" electrical conduit fitting -- which is larger, ~ 1 1/8"), as the fitting is larger than the conduit it's used with.

Antennex makes an NMO mount hole saw w/ a depth limiter so you generally don't even need to remove the headliner inside, just drill from the outside and snake the cable.
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W3LK
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Posts: 5639




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« Reply #4 on: January 20, 2008, 01:36:26 PM »

Good point!!!

73,

Lon - W3LK
Naugatuck, Connecticut
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
KE4DRN
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Posts: 3746




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« Reply #5 on: January 21, 2008, 07:28:28 PM »

hi  

3/4" Antenex works great !

http://www.radiooutfitter.com/hs34/antenex/p98693.html

73 james
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K4LNX
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Posts: 10




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« Reply #6 on: January 22, 2008, 09:21:22 AM »

On recommendation from another ham, I recently used the 3/4 step drill bit from Harbor Freight.  $7-8 for a set of 3 bits and it made a very clean 3/4" hole.
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KX6D
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Posts: 2




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« Reply #7 on: January 28, 2008, 11:27:04 AM »

I own and use a Greenlee Knockout Punch.  I drill a 3/8 hole and then insert the Greenlee punch.  It punches out a PERFECT 3/4" hole without distorting the sheet metal!  The hole is also absent of burs.  Its the only way to go!

Greenlee P/N 730BB-3/4
http://www.mygreenlee.com/Products/main.shtml?p_search=730BB-3%2F4&greenlee_category_id=100&Submit=Find

http://www.toolup.com/productinfo.asp?id=730BB-3/4&Manuf=Greenlee

If you live in Southern CA, you can borrow mine for FREE!

Dino - K6RIX
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K1CJS
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Posts: 6283




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« Reply #8 on: February 02, 2008, 07:06:44 AM »

Check the sheet that comes with the mount--if there's a sheet with it!  If not, look at the mount itself.

There are some altered knockoff NMO type mounts that only require a 3/8" hole.

I was given a NMO mount and made the 3/4" hole, just to find out it only needed a 3/8" hole.  Had to make my customer wait a couple of days (with a duct tape patch over the hole) to get the REAL NMO mount from a supplier.

I still have that knockoff NMO on the workbench--to remind myself to look at what I'm given to put in.....
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K6IHC
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Posts: 65




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« Reply #9 on: February 10, 2008, 01:22:48 AM »

Actually, most of those 3/8" NMO mounts are intended for mounting in thicker than normal panels, such as aluminum bodied vehicles.  All the major domestic manufacturers of NMO mounts offer a 3/8" *thick panel* NMO mount.
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