How to make clean 4 hole cut for Vintage Air hoses?

[analyte]

I may have done a poor job of searching, but how does everything cut the 4 holes for the hoses to pass through on the Vintage Air install? Are the holes a standard size for the hoses and grommet?

My car's firewall is smoothed, but I want to get the holes in before it goes in for paint. I've read about bulkhead leaks so I'm not considering that option.

Thanks,
Kerry

[astroracer]

As far as I am concerned the ONLY way to do this is with a Blair Rota-Broach. Hit eBay for them, best prices you'll find. These cut a very clean hole with little effort.
Mark

[dontlifttoshift]

1 1/4" if using the vintage air grommets for all four hoses. RotaBroach is awesome, but I prefer to punch them if I can get at both sides.

[analyte]

Thanks guys!

I searched ebay, and there are alot of RotaBroach bits. Do they take a specific tool to use or just a hand drill will work?

[astroracer]

Hand drill will work very well. Drill a guide hole that is tight to the pilot of the broach. This will keep the broach from wandering.
This is a hole I made for a battery cable pass-thru.
https://static1.pt-content.com/images/pt/2014/07/MVC040Fvi-1.jpg
What little burrs are left by the broach I clean up by lightly hitting the hole with a step drill. This hole was sized for a snap bushing and it fit perfectly when done.
The snap bushing and cable installed.
https://static1.pt-content.com/images/pt/2014/07/MVC041Fvi-1.jpg

[analyte]

Well, I found what I need easily. That said, the 1.25 bit requires a drill with a 1/2 chuck. I'm going to order the bit while asking all my friends if they have the right drill for it...lol

Edit: Found the 4 hole template with further google searches.


Thanks again,
Kerry

[astroracer]

You may as well pick up a drill also. You'll have the broaches and you will be wanting to use them. Even if you just go to Harbor Freight and pick up a cheap 1/2" drill it will do what you need it for.
http://www.harborfreight.com/power-tools/cordless-drills/18-volt-cordless-12-in-drilldriver-with-keyless-chuck-68850.html

[analyte]

You may as well pick up a drill also. You'll have the broaches and you will be wanting to use them. Even if you just go to Harbor Freight and pick up a cheap 1/2" drill it will do what you need it for.
http://www.harborfreight.com/power-tools/cordless-drills/18-volt-cordless-12-in-drilldriver-with-keyless-chuck-68850.html

I was actually looking at that exact drill yesterday. I like my Dewalt for around the house duties, but this might give me a garage only version.

BTW, I may be overthinking this while waiting on the Rotabroach to deliver, but do I need to support the firewall while drilling the holes? I doubt the first or second hole will be a problem, but when I do the 3rd and 4th will the metal be weakened from the missing metal?

Thanks,
Kerry

[astroracer]

No, shouldn't be an issue. You don't have to push that hard with these hole cutters for them to do their job. Make a couple of practice cuts on scrap just to get a feel for them. You will be surprised at how well they work.
That hole I pictured in the above post was on a piece of 20ga that was attached to the fenderwell on one side only. I would not have attempted drilling that hole with a step drill. I just used light pressure and it cut like butter.
Mark