body work is not my strong suit...so, I need some help or recommendations for adding holes with very clean edges....location is in the red (trunk lid)

I have an air-nibbler, but I think it would make a terrible cut for something like this

Air nibbler.. cutting wheel.. and something to clean it up a bit..

I've used the air nibbler with great success... Except when the sheet metal is double walled.. then you use the cutting wheel.. Then you use the cutting wheel or something like that (dont rember what its called) to finish it up...

PS.... Why the vents? Kinda gets rid of the "targa top holder" function of the rear trunk...


Oh ya, I just did the Dizzy hole for the v8 yesterday using this.. But I used a drill as well for starting..

make a rough cut, then file to perfection? Of course, that's just my professional opinion.

Jen

Jigsaw with fine toothed metal blades.

Alot of the MGA guys take thier hoods and have them louvered (sp). Professional shop can do this for small amount of $.

For a perfect hole that big in one pass: a huge shearing press that takes up most of a room. For a perfect hole with hand tools, something powered to cut the rough hole, a hand-nibbler to get nearly the exact dimensions, then a file to smooth the edges.

btw, if this is for the radiator in the trunk idea, I'd REALLY STRONGLY recommend you start with holes in the badge panel, and only put holes in the trunk lid when it's clear that's not enough. Some fascinating airflow studies done many years ago on racebikes by a brilliant gent named John Brittain showed that, with proper ducting, very small holes can be used to flow a LOT of air. He was doing this to provide radiator airflow with low drag (smaller inlet and outlet holes allowing the rest of the bodywork to be smaller). Drag really isn't a factor here, but if you can show that you can get adequate flow for a radiator without putting holes in the trunk lid, that would be very good to know. It certainly reduces the need for tidy bodywork.

Definitely a jig saw with fine toothed blades. Don't even try a nibbler or cutting wheel. Tape out the shape you want to cut and then cut away. You will be surprised how nice it will cut with a jig saw with sharp blades. Then use a file to clean it up.

Demick

If a plasma cutter is not in your repertoire...

I've always preferred thin cut-off wheels on an angle grinders because the blade gives me guide of sorts. Use a hole saw at the corners. I prefer variable speed pneumatics grinders because they bog down when the workpiece binds, rather than jumping the cut and jittering across the surface you're trying to keep.

I'd scribe lines in the paint, and use a heavy masking tape as a cutting line, tape on part to be kept. AND, as usual, cover any glass or paint don't want permantently speckled.

I think I'd also get a very long file, and dress the egdes, if you need straight lines. I'd cut from the top, but when filing, I'd put the trunk upside down on a sawhorse, and use the edge of the sawhorse to 'back-up' the metal to keep if from bending, vibrating.


If for cooling, I like the louvers idea too, as well as the badge panel idea. The key is to have high pressure on one side, low pressure on the other, airflow is a result.

IMO, regardless of edge quality, you'll end up with long unsupported edges of thin sheetmetal; not good. Rolling these edges would help tremendously, and yeild much needed rigidity (a folded edge would make it go flat, but you could hammer it back to shape, I suppose). It is not easy to accomplish this (to maintain straightness and trunk lid contour), but would result in a finished look, rather than an abrupt edge.

Andy

Photolithography and acid etching should give nice results. Might take a while to go through all that metal though

I agree with Jenny's suggestion of cutting first with a saw and then filing to perfection. I have an air body saw that I got from Harbor Freight that works amazingly well. With some practice you might even get a final cut with that. Otherwise, pull out some files and a dremel and go to town.

If you can't roll the edges, you could machine a frame out of an aluminum plate to support the edges, or steel so you can weld it. I'm just jealous that you have a milling machine, so I'm thinking of ways to use it vicariously

-Tony

Metal hole saw of the correct diameter for the radius you're looking for on the corners, nibbler for the sides leaving the line (I prefer a scribed type line as opposed to an ink line, It'll be obvious when you do your finish filing), and "draw" a file over the excess until the shiny scribe line disappears. Oh, and don't forget to wear good leather gloves, or you WILL get cut!

A fine carbide rotary file in a straight die grinder works great too for taking down the excess, but definitely finish by hand filing.

i agree...do it this way....

Can't find a picture of an MGA but here is a picture from the other Whine and Cheese set. Big snobs that they are

Louvers....unless your going to fill the holes with some screening material.....But louvers would look better....

of course I'd cover the holes with screen or mesh...those punched in louvers are boring and totally take away from the lines of the car...they only belong on old hot rods, any other cars and they are goofy in my opinion

Mike,hole saw in the corners then jig saw/fine blade then draw file to smooth out any rough spots. Although with Andy....long unsupported edges....not good, but if you made a grill to fit in there that was stiff enough that would support the sheet metal.

SteveSr

louvres will keep the shape of the metal better. I bet your trunk lid will sag with two big holes.

Mike, a tool I used too punch holes through thick guage stainless sheet, works like this:

Drill pilot hole.
Special tool has die cutter that bolts through pilot hole.
Tool is fastened to both sides of the work.
As you tighten bolt it draws cutting blade through your metal into the receiving die part of the tool.
Only takes a minute or two to punch any size hole you want. Perfect hole every time.

I would inquire at an electric supply house for a K.O. punch ( knock out )
or a " slug buster ".

May be a rentable tool.

KT

What size hole do you need? I can make 'em perfect in: .45, 9mm, .38, .270, .22, ......

I replied before seeing the picture of your design.

Use the punch in the inside corners like above mentioned intead of hole saw.

Slow steady jig saw sounds good. Replace blades frequently.

Put blue tape over the metal, mark your cut lines, to avoid scratching metal with your saw.

KT

Jig saw and tape it off before you cut.

LMAO

Mike, you could have the louvers made as "innies" that way you get the vent and keep the lines. also they would be kinda stealth vents.. You can buy stamped louvers from places like Coleman, then weld them in and metal finish the area.


or drill the proper radius hole in the corners, then use your trusty cut off wheel.

Kind of shocked no one mentioned a plasma cutter and template ("plasma cutter" is on my Christmas List, but I think the boss is thinking more "new refrigerator"). That'd definitely be the quickest way. And by using a template you could ensure that both holes are identical, or at the very least, damn close.

He will be missed ( and it wasnt that long ago)

There's quite a bit of surface tension on it. If you cut the holes it's gone...
After you've cut the perfect openings, you'd have to at least curve the edges to keep any rigidity

Get a f/g hood.
Slightly easier to cut
Lot easier to fix f-ups
Easy to add reinforcements if needed

What's them holes for???

cheers,

Jeroen

holes in sheet metal + perfect = plasma cutter!! they rock!

one of these days I'm going to steal my dad's cutter for good, and tell him the shady guy in the trailer down the way musta done it!

Trekkor is the only one posting here with a clue (sorry guys). You should be able to find a tool like he describes at a radio shop that caters to mobile 2-way business FM, HAM, or CB radio. People use them to cut a perfect circle for mounting antennas. I've seen them in sizes from 3/8" to 1". They are designed to cut through auto-body guage steel (12-16ga.). I assume you'd want to use said tool to cut radiused corners for your rectangular cut-outs (as in your illustration)? Should work well for that. IMHO this would be the cheapest and only practical way to cut a perfect hole without warping, edge-deforming, or otherwise screwing up the cut.

-Ben M.

I...errr, my dad... has a bunch of these 'chassis punches' for making electrical boxes. Up to 2.5" if you want to borrow one.

Don't know why you'd want to cut holes there for but as an indea you might want to think about welding edges on for reinforcement. Grind it clean and the initial cut quality won't matter as much. Or as said before fiberglass, it's easy to fix.

Sorry Airsix, but I totally disagree! We use hole saws on every access opening we cut, and there is zero deformation of the material, even in the real thin skins. Hole saws are WAY cheaper that a KO cutter of the same size (a 1/2" radius would IMO look too boxy with the size of holes it appears he's making), with just as clean of a finished hole. Besides, once he cuts out the sides, he'll have to go back with a file (rotary or hand) to smooth out the transistion area anyway. That said, I still think that a template made out of 1/8" hardboard and plasma cutter would be the quickest and easiest way to go.

My 2.5 cents

Here you go.

2\" KO punch on ebay

.Or even better - here they are in any size you want.


-Ben M.

Way ahead of his time.

I don't think that's what brad meant when he said 914s were going to go the way of the 356

I just know, having used both ko punches and hole-saws, that if Mike dropped his lid off at my house and said "please cut out these rectangles with radiused corners" I would not dare do it with a hole-saw. I've NEVER seen a hole-saw make as clean or accurately located hole as a ko-punch. In this application accurate location of the hole is really important IMHO. I'm interested in your comment about using a plasma cutter and a template - I've never used a plasma cutter. Maybe that's the way to go.

If I had to do it myself using the tools I have and know, I'd stip the lid, mark it with dykem, scratch-awl precise layout lines, use a compas to locate the center of the corner radii, center-punch and drill pilot holes, enlarge holes to size for ko-punch draw-bolt, ko-punch the corner holes, and then nibble inside the layout lines connecting corners. At that point you'd have perfect corners and rough sides. I'd then use a belt sander with ceramic belts to true up the sides of the rectangles (nibbled cuts between the radiused corners) removing matterial until you touch your layout lines. The important point here is just kissing that layout line. I say belt-sander because that will help you keep the line straight, and only a ceramic belt will hold up to the job (I recommend 3M Cubitron) At that point you should have a perfect rectangle with radiused corners and you've done zero filing or hand-sanding. Now all you've got to do is dress the edges which shouldn't take long at all.

-Ben M.

Even better!

KT

opps, I forgot to mention, it's a 'glass lid..


just kidding

I thought about the Greenlee punches Trekkor mentioned, but it seems that with such thin sheetmetal, they might tweak it.....I guess I can try it on a damaged donor lid first

Whats it for?

Well airsix, I guess we'll have to "agree to disagree" on this one.

The hole saws we use are this type (note the "major aerospace corporation" reference in the discreption. I work at the military aircraft division of the same corporation in St. Louis- see Avatar for clue).

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...3834474077&rd=1

These aren't the hardware store type hole saws you'd use around the house. They're made specifically for metal, and cut it like butter (titanium in my case), leaving an exceptionally clean hole. We're in total agreement on using scribe lines as opposed to other marking methods; when the shiny line disappears, you're there. As for the belt sander, I've never thought about using that tool for grinding metal. I suppose with the right belt, it'd work like a champ. I'm a fan of the rotary file, I guess because I use them alot. We use hand files (bastard) to finish the opening because of the close tolerances required between skins and the access doors (which incidentally is how I got nicknamed "Special K" by a friend/co-worker. I'm way to anal about how the assembly turns out...pretty sure he didn't mean it as a complement though , whatever works for you "is" the best method.

Oh, and by the way, that's a GREAT DEAL on those ebay hole saws so far. If anyone on this board buys them, contact me about the special arbor you'll need to use them.


Kevin

er, I mean, good question...


ventilation for the VR6 perhaps???

Mike,
Lot's of good suggestions. On the reality rod builder shows, I've seen the fabricators use hole saws and scroll saws and then clean the edge up to the drawn shape with grinding wheels. These are $100k rods with new metal bodies...
Felix

Im tinkin radiator or intercooler (come on mike, I know your thinking turbo...)

ROFLMAO!

Considering the source I did almost fall out of my chair when I read that.

Cool. If it works it works. And I like any tool that can cut Ti like butter (I work with it too and know how hard it is on cutting tools)

-Ben M.

Maybe the holes are for a second set of air horns for the flat 12 conversion

I'm thinking that Mike's tail light and trunk seals work too good, and he wants to increase the amount of water intrusion into the rear trunk area. Even with the modification, I doubt it could compete with mine!