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How to cut round holes?

R

riobison

Well Known Member
I'm going to be cutting a couple of round holes in my RV 4 to install a pair of ULTIMATE VENTILATOR's

So, I don't see anything much in the way of using circle cutters that are attached to the end of a drill with a pilot bit then followed by a hole cutter such as what is used on wood.

So is there anything designed for aluminum built similar to this?

Or is my best bet is to order the Circle Cutter that is on Air Craft Spruce that looks like Scribe powered by a drill?

http://www.aircraftspruce.ca/catalog/topages/holecutter.php?clickkey=29428

Any recommendation on what to use for tools for this as well as what to do or not do? I will practice on some scrap aluminum 1st to make sure I get it right the first time.

Thanks

Tim
 
I guess the real question is where are the holes located? How I would approach this would depend on the orientation of the place I had to cut the hole.
 
good advice on its way!

Tim,
I think most guys will agree that the 'fly-cutter' is the most medieval torture device known to man! pretty tricky to use, many fingers lost etc.

ideal is the punch....

http://www.aircraftspruce.ca/catalog/topages/knockout2.php?clickkey=8331

but very expensive. if you plan out your entire panel, you might get a decent price from an aluminum fab. shop that has a simple router table.

If just adding one instrument, get friendly with the shop that will end up doing your bi-annual altimeter recert and other tricky avionics stuff, they may be willing to lend or 'rent' you what you need.
there are some pretty slick attachments for a dremel tool. you can build a jig to control the hole size, and follow with the dremel head....with only some minor cleanup needed after.

old skool: tin snips and a file, case of Molsons', etc.
 
Apparently, you are not the builder, no worries,

Just take a compass, with a sharpie, draw a circle and mark the material to be removed. Check behind it so you know what you can damage, Drill a series of holes, then use a hand nibbler and a piece of 80 or 100 grit sand paper to make the hole smooth and round. Wrap it around a piece of PVC pipe near the correct diameter. Probably 45 min per hole.

I am a tool guy, but if there is an odd size and I don't want to wait or spend money I would not hesitate to use this method. Low skill threshold and good results.

It will be less prone to error, and you won't have a tool sitting around after a single use.

If you really want a punch, check Horror Freat. They have Greenlee copies for a reasonable price.
http://www.harborfreight.com/hydraulic-punch-driver-kit-96718.html
 
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I used Bill's method, except I used a Dremel tool to connect the small holes, then a sanding drum, maybe 2" in diameter, chucked up in a hand drill to sand down to the Sharpie line. Got the sanding drum attachment from Ace Hardware, less than $10 IIRC.
 
Hougen Rotacut

I've got some of these in various sizes.

http://www.hougen.com/cutters/sheet-metal-hole-cutters/Holcutters.html

http://www.hougen.com/cutters/sheet-metal-hole-cutters/Rotacut-sheet-metal-hole-cutters.html

They aren't cheap but they cut nice round holes thru just about anything. I once cut a 0.75" hole thru a piece of 0.375" thick high strength steel with a cordless drill. These are overkill on thin aluminum but will last forever. I bought a set of the smaller sizes 20 years ago and they are good as new. Excellent quality. Just use some coolant/lubrication with them so you don't overheat them. Hougen makes a "lube stick" that works great.

Very easy to use and come in a variety of different sizes. If I need to cut a hole larger than what I have with my Unibit, I go with the Rotacut/Holecutter's.

Just look online for them. Several places sell them.

I hope this helps.

Jeff
 
That's how we did: We used hole cutters with a pilot drill bit. Cut out a plug of thick wood. Drilled a hole in the aircraft structure with the same diameter as the pilot drill bit. Attached the wood plug with the bolt to the structure. Removed the pilot drill bit from the hole cutter. Cut the hole in the structure, using the wood plug as a pilot/drill guide. It's good to have some support from the opposite side of the sheet (especially if thin) to cut. We used a wood block with a hole for the bolt head/nut.

We used that method to cut hole in aluminum and stainless steel (firewall) up to 2 inch in diameter. Worked out well for us.

16531991306_290c0a78ab.jpg
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Depending on the size of the hole, a regular bi-metal hole saw works just fine. The fly cutter works well also. I have used both with no issues. Just make sure you buy a decent hole saw, the cheap ones have a lot of runout.
 
Use a wood bit... Really!

After testing it on practice material, I started using wood bits on all sheet aluminum penetrations. It has to be a bit with the spikes on the edge and they're only good for about 10 holes each, but super cheap, come in almost any size and make a perfect hole. Just drill a .040 pilot hole and then final drill. BTW, It will NOT work for stainless! Hope this helps someone.

Lance
 
fly cutter

Tim, I have used a fly cutter for many years in wood working projects before I started to use it to cut large holes in aluminum. Highly recommend not ever using it free hand whether in wood or aluminum. It can be a very dangerous tool but makes great holes when used properly in a drill press and having a solid backing behind the material.
Good luck.
Rick
#40956
Southampton, ont
 
Vents and more cracks in the rudder RV4

Thanks for all of the ideas. Lots of tools that I was not aware of. Yes I'm not the builder but the repair man as I'm the owner here in Canada.

Just adding some air vents as this little RV 4 gets some hot up here in the Okanogan. In the summer we get into the low to mid 40+ deg C. Normally we cruise at 8 to 10,000 ft where the air is cooler but until we get there my GF and I need a little more air circulation.

The hole will be 1 5/16" or 34 mm for the Vetterman Vents. I think I will try a good bi metal circle cutter as it sounds like these bits are doable as long as a guy takes it easy.

My rudder is now starting to develop new cracks along the trailing edge. It seems the more I side slip this the more cracks I get. So, next project over the summer will be to build a new rudder with heavier skins.

Thanks

Tim
 
riobison said:
Thanks for all of the ideas. Lots of tools that I was not aware of. Yes I'm not the builder but the repair man as I'm the owner here in Canada.

Just adding some air vents as this little RV 4 gets some hot up here in the Okanogan. In the summer we get into the low to mid 40+ deg C. Normally we cruise at 8 to 10,000 ft where the air is cooler but until we get there my GF and I need a little more air circulation.

The hole will be 1 5/16" or 34 mm for the Vetterman Vents. I think I will try a good bi metal circle cutter as it sounds like these bits are doable as long as a guy takes it easy.

My rudder is now starting to develop new cracks along the trailing edge. It seems the more I side slip this the more cracks I get. So, next project over the summer will be to build a new rudder with heavier skins.

Thanks

Tim
Click to expand...
The bimetal hole saw will work fine for that small of a hole. If you can, have an assistant hold a piece of ply or backing board against the back side. That will give your pilot drill more support and help to keep the saw square. Use boelube, the paste type, and just make sure you are making good chips and not overheating the sheet. You don't want any warping. A sharp or new saw is a must.
Your cracks are from poor construction technique. Build them right and you will have no worries even with .016. However, not much penalty in using .020 since you have to build them anyway.
 
Hello Ron,

I have a hanger here in Oliver. I'm at the airport most days during the week. We should get together for coffee. I'm assuming your in Penticton?

Tim
 
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