Enlarging an existing hole

[HookWorse]

I have a 3" hole in a tractor hood that I want to enlarge to 4-1/2". What would be the best way to go about this and have it look proper? Or should I say, what equipment would be needed and what type of place should I be looking for to do it? Thanks

 

[king nero]

tractor hood => how thick is that?
could you use a saw like this, with the appropriate blade? + finishing with a dremel or file?

 

[Rentawrench]

If you have a hole saw kit, clamp a 2x4 to inside of hood under hole the use 3in hole saw to get center,( just the small pilot hole) then use that center hole an put a 4 1/2 saw in an cut.

 

[Herb]

Yes,X2

 

[Jim Stabe]

Trace out the new hole outline and use either left hand aviation snips (red handles) or a saber saw with a fine tooth blade. You can lay masking tape around the outside of the hole if you don't want to scratch the paint.

 

[Underdog]

If you have a hole saw kit, clamp a 2x4 to inside of hood under hole the use 3in hole saw to get center,( just the small pilot hole) then use that center hole an put a 4 1/2 saw in an cut.

+1
Also for holes that you can't get under well, I've made a wood dowel from scrap and driven it into the hole just tight enough to drill, find center, re drill, knock dowel out.

 

[HookWorse]

Wow, and I was expecting you guys to say there is some ultra sonic hyper driven lithium crystal boring device that is the only way it can be done.

 

[Lotek]

Starrett Oops Arbor a19, Put a 3" saw on the inside as a guide, 4.5" on the outside, done.

Not lithium crystal driven, but very handy.

 

[tomd]

Is this hole round? Or oval?

 

[ZRX61]

Plasma cutter!!!

 

[HookWorse]

Is this hole round? Or oval?

Round hole, where the muffler goes through. Right now, the pipe comes up out of the manifold, through the hood, and the muffler clamps to it. I want to shorten the pipe, and lower the muffler so the clamp is under the hood instead of above it. As it is, to take the hood off, you have to remove the muffler because the hole is smaller than the diameter of the muffler.

 

[HookWorse]

Plasma cutter!!!

That may be a tad hard on the paint.

 

[back2class]

I would also think a round ginder, either a disk/wheel in a die grinder or a small drum insert for a die grinder with good oxcide paper on would work well. Just follow the outline you would draw first. I would use the hole saw if you have them and die grinder if you didn't and own die grinder. Snips will bend the steel too much.

 

[Quiksilver]

Starrett Oops Arbor a19, Put a 3" saw on the inside as a guide, 4.5" on the outside, done.

That's awesome! Didn't even know that those existed. This forum rocks

 

[bad_idea]

i have been meaning to buy one of those starrett opps arbors! this sounds like a perfect project to buy one for. (you, not me tho)

 

[StumpXJ]

That's awesome! Didn't even know that those existed. This forum rocks

+1. Had no idea. Thats ingenious.

Thanks!

~ Stump

 

[gorilla]

If you think that a hole saw will be kind to the paint it's obvious that you have never used one. The best tool would be a large hydraulic knock out punch or a sharp pair of aviation snips./

 

[mdbeck1]

You could draw the circle and use an air nibbler (requires an air compressor).
http://www.harborfreight.com/16-gauge-air-nibbler-96661.html

...or they make a hand version as well.
http://www.harborfreight.com/compact-hand-nibbler-65895.html

 

[klhitman]

what i have done to make a large hole larger is take a hole saw of the size i want and put it on the arbor and then put a hole saw of the size that is already there inside of the hole saw that i need. works for me and keeps it it centered

 

[anotheroldguy]

If you have a hole saw kit, clamp a 2x4 to inside of hood under hole the use 3in hole saw to get center,( just the small pilot hole) then use that center hole an put a 4 1/2 saw in an cut.

good idea. clever.

 

[Alchymist]

gauge-air-nibbler-96661.html[/url]

...or they make a hand version as well.
http://www.harborfreight.com/compact-hand-nibbler-65895.html

I'll guarantee you that if he uses this he will have blisters larger than the hole he's cutting!

 

[lilredex]

This is the one I'd try. I have one and it cuts smoothly as I remember, but haven't used it in a while. Can try it out again in the AM if you wish. Let me know..........I mainly work with 18 Ga.

http://www.micromark.com/Sheet-Metal-Shear,7163.html

 

[Milton Shaw]

If you have an electrician friend he might have a greenlee slugbuster Knockout punch that would do it with just a few turns of the wrench. Knockout punches are used to put holes in panels for conduit and a 4.5 inch is probably available. My set of punches goes to about 2" but an industrial electrician would have bigger ones. You might be able to find one at rental yards also.

 

[speed bump]

If you think that a hole saw will be kind to the paint it's obvious that you have never used one. The best tool would be a large hydraulic knock out punch or a sharp pair of aviation snips./

Mask out where you are cutting and your good to go. Good luck cutting a tractor hood with aviation snips.

 

[hunter1151]

Ditto that---------

 

[hunter1151]

If you think that a hole saw will be kind to the paint it's obvious that you have never used one. The best tool would be a large hydraulic knock out punch or a sharp pair of aviation snips./

This is especially true if it isn't flat!!!

 

[Frank The Plumber]

fasten a piece of hardwood to the back side of the 3" hole using screws within the 4 1/2" dimension. Center a pilot hole in the center of the 3" hole into the hardwood. Use a fine 4 1/2 "metal bit with a pilot bit into the hardwood hole and lubricate with a dish soap and water solution this will help to cool the paint so it does not shrink peel from the heat.. Be patient and hold the drill steady or use a press if you have one.

Do a test sample first to be sure your bit won't catch and travel.

 

[HookWorse]

I called a guy I know in a commercial electric company, asked him how big their knock out punches go. He said, 4-1/2", why?

 

[Rickochet]

And we have a winner!!!!!

 

[Altec]

Starrett Oops Arbor a19, Put a 3" saw on the inside as a guide, 4.5" on the outside, done.

Not lithium crystal driven, but very handy.

That is a cool arbor. I would normally say to use the 2x4 trick, but that is handy right there!

 

[nkachur]

I would second the knockout punches. They produce a beautiful smooth hole with very few burrs and no real cleanup. Only downside is they are pricy to buy.

 

[Alchymist]

Check the actual size on electrical knockout punches - they go by pipe size, not hole size. Actual size is usually larger than indicated. Example, 2" KO will punch a 2-1/2 inch hole. "Chassis" punches, used in electronics, however, punch indicated size. Just something to be aware of.

 

[HookWorse]

Ok, will do. Thanks