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right now i'm ready to cut the holes in my roof. i followed motormans install link, (good link)but he says to use a 7/8 knock out??? he says 7/8 twice. i'm thinking thats a typo. that seems a little big. the center hole would be awfully close to the mounting holes. (he also reccomends drilling those big also). my green lee knock out set has 1/2"-3/4"-1"-1 -1/4". i'm thinking i'm going to use the 3/4". i think i would feel more comfortable with as much sheet metal i can have touching the gaskets. am i off base? any thoughts? thanks.
wait i think i figured it out. the 1/2" knock out really makes a 7/8" hole.
Last edited by spinella; Jun 26, 2010 at 11:26 AM.
Reason: answered my own question...i think.
Is that for the wires to pass through? Does seem a little big to me, but still under 1". If only for the wires, I would cut that size in half. 7/16" will be more than enough to pass two wires through.
read my edit above. the large hole is for the lights plug to sit in. then there are two smaller holes for the mounting studs. the 1/2" knock out has a 1/4" pilot hole, what got me wondering was the larger knock outs have a much larger pilot. seemed silly to pilot a 3/4" hole for a 7/8" knock out. thanks for the reply....here goes nothing.
wait i think i figured it out. the 1/2" knock out really makes a 7/8" hole.
This is exactly right. It's not 1/2 inch, it's 1/2 conduit trade size, which is 7/8 inch. The knockout will have a 3/8" bolt, so you will drill about a 13/32" pilot hole. Sounds like you're good to go.
I much prefer the knockout over the step drills. Far fewer hot chips.
thanks you, one more quick question. i have the center holes marked out-5 1/2" off the rubber windsheild gasket as per motormans wright up. do all the lights aim perfectly straight or do they curve with the windsheild. in other words are the mounting holes on th same curved line that the center holes on or are they drilled so that the lights are all absoulutly fowarded.
when I did mine, I got a 4' fiberglass bubble level and marked a long straight line throught the center holes of each pair of lights. Then I put the mounting holes along these guidelines.
I used a fiberglass level because it would bend enough to form to the roof of the truck.
Did you put silicon around the lights? I did and I'm glad for it, cause one of the nuts backed off the lights and the silicon kept it from leaking. One of these days I'm gonna pull the headliner and locktite all the buggers.