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09-17-2008, 10:52 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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I have had success...
...with a Sears drill press at 600 rpm and a General Brand (from Ace hardware) fly cutter.
Clamp everything down and press very lightly - cut the least you can off in every revolution.
For increased accuracy, I have removed the drill bit and replaced it with a 1/4 inch steel rod section. If you have a clean pre-drilled hole in the plywood backing piece, this will stop any side cutting, and movement, that the original drill bit might do as it penetrates the plywood.
If my reading of the tables is correct, a 650 rpm cutter for a 3 1/8 hole in aluminum is only 30% overspeed... That's for a 350 ft/min cut... some charts show a 600 ft per/min....
A liquid lubrication helps - the non-oil cutting fluids seem to be OK and less messy.
I got good instrument panel holes this way, and even large wing rib lightening holes (before Van cut them out for you...  ...)
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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09-17-2008, 10:57 PM
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Join Date: Sep 2007
Location: Albuquerque, NM
Posts: 659
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I've been using the Harbor Freight one. It scares the heck out of me everytime I use it due to the wobble. I also have to resharpen the cutters every hole.
I always clamp the piece on top of some MDF and use lots of boelube. If I had more holes to cut I'd probably get a good one like the one Avery sells.
__________________
Andy Compton, PhD EE
RV-10 - #41414 (building)
RV-9A - N643AC (built,flying,sold,missed)
My blood and sweat, the Wifey's tears
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09-18-2008, 01:39 AM
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Join Date: Mar 2007
Location: Sonoma County
Posts: 3,821
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I used a GENERAL brand mounted in a 90 degree head connected to my cordless drill set on low speed..... used about 60 rpm to cut a 1.5" hole in the rear baffel mounted on the motor............... SLOW..... IS VERY GOOD!!! This was just above a stall speed for the cutter, and had very good control.
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09-18-2008, 05:48 AM
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Join Date: Feb 2005
Location: Huskerland, USA
Posts: 5,862
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I use the fly cutter in a hand drill to cut holes in canopies for snap vents.
As far as the measurement, here is what I do. Take a dial caliper and measure the distance from the outside of the cutter to and including the center drill. Subtract 1/2 of the center drill diameter. Do the reverse to set it to a dimention you want. Works every time. Cut a test hole for accuracy.
On metal are you using a lubricating oil on the cutter?
__________________
RV-7 : In the hangar
RV-10 : In the hangar
RV-12 : Built and sold
RV-44 : 4 place helicopter on order.
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09-18-2008, 05:58 AM
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Join Date: Apr 2006
Location: south carolina
Posts: 1,111
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i used the avery one. @30.00$ and one from lowes @10.00 $ both work great, look identical, except one is smaller.. no lube , clamped when possible, cover the surface with tape sometimes, 620 rpm's
clamping down the part really helps. however i dont always do that and that is risky to say the least. clamp when you can..i also cut the hole undersize about 1/16 to allow for deburring.
i found the harbor freight one to be useless and it cost more than the one from lowes.
now a hole saw i cant get to work on alu for ****.
__________________
William Weesner/ still kicking.
Last edited by cytoxin : 09-18-2008 at 07:07 AM.
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09-18-2008, 06:02 AM
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Join Date: Apr 2006
Location: south carolina
Posts: 1,111
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Quote:
Originally Posted by Geico266
I use the fly cutter in a hand drill to cut holes in canopies for snap vents. 
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Larry , you are a brave man...i salute you. 
__________________
William Weesner/ still kicking.
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09-18-2008, 06:25 AM
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Join Date: Sep 2006
Posts: 66
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I have the same one ...worked fine..
I think I have the same fly-cutter from Sears. I have the cheapie Ryobi drill press, which only goes down to around 600RPM as well.
I had no problem cutting the tie-down spacer holes with it. I set the drill press to the lowest speed, clamped down the spacers on top of a small piece of 2x4, and used lots of the cutting lubricant they sell at Harbor Freight. As I was doing the first one, the cutter did get stuck in the aluminium, and the drill press got real angry real quick.  After that, I learned to put very little pressure at a time. It was messy with all the cutting fluid, but the result was a very nice hole.
BTW, I started out with the harbor freight fly-cutter, but just watching it spin scared me enough to go buy the sears one....
Good luck...
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Luis Orozco
Austin, TX
RV7A - Flying!
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09-18-2008, 06:53 AM
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Join Date: Jan 2005
Location: Roy, Utah
Posts: 1,144
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fuel tank repair
We just cut 5 5" diameter holes in the baffle plate in an RV6 fuel tank last Sunday using 650 rpm on a benchtop drill press and the Sears fly cutter. The biggest problem was getting the workpiece square to the cutter.
Steve
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09-18-2008, 07:07 AM
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Join Date: Feb 2005
Location: Huskerland, USA
Posts: 5,862
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Quote:
Originally Posted by cytoxin
Larry , you are a brave man...i salute you. 
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Trust me, I have a beer afterwards.
The trick is go 1/2 way though one side and then finish it on the other side. Maybe that would work good for metal and a drill press also?
__________________
RV-7 : In the hangar
RV-10 : In the hangar
RV-12 : Built and sold
RV-44 : 4 place helicopter on order.
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