NMO in a 7/8" hole -- will it work?

[redshift]

Will an NMO mount fit OK in a 7/8" diameter hole or will that be too large?

I have a 1/2" hole in my truck roof right now that has a Firestik CB antenna mount in it (3/8"x24 stud mount). I'd like to widen that hole so I can put an NMO mount in it's place for a much wider antenna selection. I have an electrician's punch that makes the most beautiful and clean holes you can imagine, but they are 7/8" in diameter (it's for making holes to attach 1/2" ENT to metal boxes). I'd like to get away with not buying another hole saw just to install one more mount, plus I probably wouldn't be able to widen an existing hole with a holesaw anyway, I'd have to use a step bit.

Would that 7/8" hole size work, or do I have to ream it out to 3/4" with a step bit and make a mess?

I don't have any NMO mounts in hand or else I'd measure myself, but I figured I'd pose the question here just in case any mobile radio installers knew off-hand.

 

[jackj]

Nope, it won't fit. Or I should say that it will fit but the antenna mount will pull out of the metal the first time the antenna hits something. Break down and buy a 3/4" punch, check Harbor Freight. They don't carry Greenleaf but you might get a China knock-off.

 

[FFPM571]

Id use a step bit. go one step at a time. As far as mess ..shop vac.... problem solved

 

[Mtnrider]

These work real nice too

Antenex HS-34 [HS-34] - $31.95 : The Antenna Farm :: , Your Two Way Radio Source!

 

[W2NJS]

An NMO mount is built to an extremely close tolerance for a 3/4 inch hole. Anything smaller it won't seat fully and anything larger it will pull out of the hole, and sooner rather than later, believe me.

 

[redshift]

OK, sounds like the consensus is 3/4" or nothing. Thanks for the input, everybody!

I have a step bit and a shop vac. Just gotta watch out for those blazing hot little shavings that always seem to find a way to lodge in your skin.

 

[jim202]

OK, sounds like the consensus is 3/4" or nothing. Thanks for the input, everybody!

I have a step bit and a shop vac. Just gotta watch out for those blazing hot little shavings that always seem to find a way to lodge in your skin.

Have you ever heard of running the drill at something other than max speed. Step drills don't last long when you heat them up. Your comment about "blazing hot little shavings" is a hint that the speed your using is too much. Your probably turning the metal your cutting through blue also.

 

[FFPM571]

These work real nice too

Antenex HS-34 [HS-34] - $31.95 : The Antenna Farm :: , Your Two Way Radio Source!

That is the saw I use. I install radios professionally. But, He has an existing hole and that would not work for what he needs. The best bet is a step bit.

 

[gmt0000]

When you go to drill out the hole with your step bit, duck tape a Dixie cup under the hole, this will catch all of those shavings, protect the interior and make clean up a snap.

Dale

 

[com501]

If your hole is above a headliner, slide a piece of cardboard in there with some sticky tape on it. I can't tell you how many times new installers dropped hot metal through those old VW Bug headliners.....

 

[cmdrwill]

They make an NMO mount that fits in a 3/8 dia hole.

 

[CCHLLM]

They make an NMO mount that fits in a 3/8 dia hole.

.......But that won't solve anything. A 3/8 mount won't work in a 1/2 inch hole.