What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

New Circle Cutter

cka357

cka357

Active Member
I just found this sheet metal circle cutter at a HVAC supply house. It's also available at Home Depot. It consists of a three flute endmill that rides on a couple of bearings. The endmill inserts into your drill. It's much better than a hole saw or a fly cutter for cutting access holes in the fuel tank. Here's a few pictures of the operation. And the brand name is Malco.

CircleCutter1-1.jpg


CircleCutter2-1.jpg


CircleCutter3.jpg
 
These work great on aluminum, they've been around for quite a while. A small angle grinder gives very precise control...

I tried mine on my stainless firewall but did not even get penetration before dulling the bit. Went back to the multiple hole / dremel method. Maybe at slower speed with lots of lube?
 
Yup, I purchased mine 19 years ago. It is a useful tool for the job described above, tank holes, but I have not really used it for too many other jobs as it is quite slow. Another tool to add to your tool box.
 
Malco Circle Cutter

Here's the link to the Malco circle cutter. Like stated above... $60

http://www.homedepot.com/h_d1/N-5yc...d=10053&langId=-1&keyword=malco&storeId=10051

Stainless requires that the RPM be less than that used on AL. (about half) Also, when machining stainless, if the bit turns without bringing out a chip then you can be for certain the bit is dull. Some variations of stainless are free machining. Others require a bigger hammer.

Happy Machining,

Chuck
 
quality drill bits

Hi,

Does anyone have a good source very high quality drill bits?

Thanks,
Mickey
 
Quality Drill Bits

There's tons of drill bit suppliers on the net. I use MSC for my source. They are quick to deliver. They give you a good description of the bit material and coatings when using their sort menu.

http://www1.mscdirect.com/cgi/nnsrhm

Search for aircraft drills.

Cleveland or Precision Twist Drill are two quality manufacturers.
The 135 degree split point really helps to prevent bit walking as well.

Chuck
 
Circle cutter

Being a part time machinist, my guess is that the bit is High Speed Steel (HSS). Slowing the speed down will help, but just delays the inevitable. If the blade can be removed, and looks like a normal bit, you should be able to find a carbide bit to replace it for stainless work. Go slow as suggested above as the bit will grab and turn your stainless into scrap at high speed. Take your time and you should get a perfect hole.

303 Stainless is free machining although shallower cuts, slower speeds and feeds are required.

304 Stainless will eat carbide for breakfast if you go just a little to fast or heavy cut. And forget about tapping it by hand.

Ask me how I know.
 
MSCDirect

cka357 said:
There's tons of drill bit suppliers on the net. I use MSC for my source. They are quick to deliver. They give you a good description of the bit material and coatings when using their sort menu.

http://www1.mscdirect.com/cgi/nnsrhm

Search for aircraft drills.

Cleveland or Precision Twist Drill are two quality manufacturers.
The 135 degree split point really helps to prevent bit walking as well.

Chuck
Click to expand...
Chuck, thanks for the tip on MSC Direct - I have not visited their website in a long time and I can see it's really made a lot of improvement!

Regards,
Mickey
 
Great Tool!

I bought one of these, a Malco HC-1, from Amazon to cut the lightening holes in the wing ribs of my RV-3B. The holes were very easy to cut, with none of the danger associated with a fly-cutter.

24fe8e8.jpg


For these holes, it was hard to clamp them down and still get a full swing of the tool. I started with this corner clamp and one more, and later added a third and removed the corner clamp - for each rib.

Since the tool rides on a pilot, when I got near the end of the cut, I had to be sure that the tool was firmly pressed against the backing wood piece to keep it from wandering. This wasn't hard and there were simply no issues at all. All 23 cuts went real easy. Yes, the RV-3B wings are symmetric - I made a practice cut before attempting the ribs.

I used a Sioux air drill and used about 95 psi. My compressor needed to recharge five times for the drilling.

The hole was slightly rough and needed cleaning up. I used a drum sander in the drill press for that, finishing off with a Scotchbrite drum in an air die grinder. A piece of 220 grit sandpaper would have done as well, been quieter and taken considerably longer. With the air die grinder going, the air compressor was on constantly, but never dropped below 100 psi. I was running about 95 to the grinder motor.

Dave
 
Last edited:
Has anyone used this tool to cut access plates in rear of fuel tank when the tank is already built?

Wondering whether there's enough clearance for the tool to clear the skins when cutting into rear baffle.

Thanks,
Tom H.
 
I have used one to cut access holes in the rear baffle. You only get part arcs however before the frame hits the flange on the baffle. I finished mine freehand with a dremel and carbide burr designed for aluminum, then a sanding drum in a drill.
 
Hi Guys,

I just cut my first panel using a Malco hole cutter and each hole came out perfectly. Using a cordless drill, it took about 60 seconds per hole and is completely safe. I laid the panel down on a piece of pink styrofoam board to do the cutting. My neighbor loaned the cutter to me. Turns out that he helped design this tool way back when. One third the cost of a hole punch and adjustable to just about any size hole you want.
 
Last edited:
Stainless steel not only requires slower RPM, its properties also mandates a "feed rate" sufficient to continue cutting in "new" material.

Once a tooth of the end mill cuts through the material, it is work hardened to a particular depth. If you advance the cutter just enough, you'll be cutting in relatively "soft" material and the cutter won't (first) "appear" dull and (second) won't become dull from dealing with work-hardened material.

Usually this is successfully achieved on a mill that provides a driven, adjustable, feed rate.

FWIW

mjb
 
I had to do a 2" hole in my firewall for the cabin air. I tried a hole saw, with some trepidation. I was worried that it might grab and damage the surrounding material or stretch it out of shape. I need not have worried. The hole saw didn't do anything except get really hot and smooth - the teeth were basically burnished smooth. So I used a unibit, an air nibbler to open up the hole and remove material and then a carbide burr, which did catch a couple of times but I managed to get a neat hole. The hole saw did a nice job of scribing the circle so that I could follow it with a burr. I gained new respect for stainless.

I would be quite nervous about using something like this on stainless. It just doesn't look rigid enough. The chip loading has to be very uniform or the cutter will dig in. That's why fly cutters are called fly cutters, because they like to fly across the shop, or make the work fly across the shop (haha old joke). A very sharp knock out punch is much safer, but it is hard to justify for one hole.

If anyone has used this on stainless with good results I would be curious to know. My skepticism might be unfounded, or biased by my previous bad experiences ducking flying projectiles.
 
You must log in or register to reply here.
Back
Top