Cutting large holes through steel -- how do you do it?

I want to mount some strobe LEDs to a part of my rear frame that is between the bottom of the tailgate and the top of the rear bumper. These are the lights:



The rounded parts on the ends are about 1-3/16" diameter. I'm not skilled at all with metalworking, in fact I'm a complete noob when it comes to working with metal. But I was thinking of boring two adjacent holes with a bi-metal hole saw and then cutting out the straight parts in between with a cutting wheel. Would this be a sketchy move?

My main concerns are:

1) would a hole saw make clean holes through that steel okay? It's about 1/16" thick
2) would a cutting wheel work to cut away the excess material between the holes?
3) I'm concerned about potential for frame rust if I cut/bore the steel. What would be the best way to prevent a potential rust fest?
4) and most importantly, will holes of that size seriously comprimise the strength of that cross member, and if so, does that cross member really do anything structural?

Sorry if these questions sound naive, I'm just trying to figure out a way to mount these things as stealthily as possible.

 

it sounds like it should work fine. even though its only a cross member, i still wouldnt mess with my frame. you should try to make some sort of L bracket mount

 

Do you plan on mounting them straight into the frame? I don't know how much room you have between the frame, and the bumper/whatever is there, but I would reccomend getting a bracket to cut into, then mounting the bracket onto the frame.

I was gonna do basically the same exact thing but with those strobes from ebay (same ones you have), then I was going to mount a couple lights like this onto a headache rack I have not built yet.

 

What he said ^
Bracket would be best.

Also, the way you suggested of cutting the holes would work absolutely fine. You may have to use some kind of die grinder to make it a little bigger if it isnt quite big enough.

 

Why do you need to cut such a big hole? Couldn't you just surface mount them and drill a small hole for the wire and mounting stud?

 

Initially I wanted to flush mount them to that portion of the frame between the bottom of the tailgate and the top of the bumper, but they are too deep and there isn't enough clearance for the bottom edge of the tailgate to swing down when you open it.

I though about doing L-brackets to mount them under the bumper but that would reduce my departure angle for wheeling...the lights would rip right off if I crawl up something steep and bottom out on my rear bumber.

Thus, I came up with the above idea of cutting holes into that frame cross member so just the lenses of the strobe lights poke through, and I could make some kind of brackets to hang the lights from somewhere inside that frame cross member.

My main concern at this point is weakening that cross member (not sure if would even matter, if it doesn't carry any structural loads), and the potential for rust.

 

I decided that those cheapo ebay strobes kinda suck in daylight, so I'm replacing them with these ones which are like 10x more powerful.

 

How big is the cross member? Its too dark for me to go look and I can't remember haha.

 

Where are you getting them? I thought about just buying some normal LED clearance lights and wiring them up to a strobe controller.

 

There's a trailer supply store in Seattle near Boeing Field (can't remember the name, but I can let you know if you are interested). They have these lights for $40 each ($80/pair). They are Maxxima 4 LED strobes, no power supply or controller needed. They have like 20 flash patterns built in that you can choose from and all you need to do is wire them to an on-off switch with a 3 amp add-a-circuit. They are 100% weatherproof and have like a 10 year warranty.

 

This X2

Find some other method man. Dont risk the integrity of your frame for some lights you dont NEED.

my 0.02$

 

Oh wow. How do you control the patterns? And it looks like there is two separate colors in each unit? Does that mean you can pick between the two colors?

 

Oh I ended up buying a set of those cheap leds. They are 6x3, and there are six amber ones. From some input I have heard, If you use a different power supply besides the one they come with, you can almost double the brightness, without worry of burning them out or shortening life span. Just a thought if you are keeping yours!

Also, if you do that, you can buy some normal amber clearance lights and wire them into the circuit. You could save a pretty good chunk of money that way I am guessing.

 

Plasma cutter for thick steel & wherever you cut holes make sure you center them in the middle of material cutting... (away from edges, other holes,etc; any large holes with need a little subframing ...

 

Here are some pix of the spot that I was thinking of boring/cutting. I outlined one of the approximate spots in red.

The frame cross member is a C-channel and already had a rectangular hole in the middle, I would guess to pass wiring thru for a trailer.

The existing LED lights in the pic are the cheapo ones from ebay (planning on removing them)...they are just stuck on with double sided tape:




Here's the spot with the tailgate removed:



And the frame cross member from the underside:

 

The ones I have are solid amber, not amber-white like in the pic. You control the patterns by pre-programming each individual light by powering it for 1 second at a time to "scroll thru" the patterns to choose from until you find the one you want, then you can set it just do that pattern.

 

Personally I'd have no issue doing that just as you've described.

 

Yeah, I don't think I'm overly concerned about it either, the more I look at it.

So what's the best way to safeguard against rust? Brush on some Rustoleum onto the cut part?

 

just do this

 

Yeah after looking at your pics ben, I wouldnt be concerned about the holes being there. As for rust, a good rustoleom paint should do the trick. The only hard part will be gettting up there to cut the holes into the cross member. If you want help doing this at all, I can help you out. And you can help me het my ebay lights on. Not that it will be hard haha