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  #81  
Old 12-26-2013, 02:21 AM
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GWIZ GWIZ is offline
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Quote:
Originally Posted by johnyradio View Post
Still awaiting these two shipments:

nibbler/shear (flat blade, doesn't punch little half-moons):
http://r.ebay.com/Pd8EA1
In my post #55 I refused to call that a Nibbler siding with FabberMcGee.


Look at the picture in this e-bay link, the back ground you see a magnified rolled up endless chip guessing 3/32" wide.
Its a pair of scissors that makes a 3/32 wide cut (it does not snip off the chip with each nibble)"

http://www.ebay.com/itm/Precision-Ha...#ht_1437wt_736
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  #82  
Old 12-26-2013, 02:29 AM
johnyradio johnyradio is offline
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Quote:
Originally Posted by GWIZ View Post
In my post #55 I refused to call that a Nibbler siding with FabberMcGee.
Sorries, they call it a 'nibbler' in that product page.

Quote:
you see a magnified rolled up endless chip guessing 3/32" wide
OK, i see, it cuts a 3/32" gap in my material. Maybe i can compensate for that? Will test.
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  #83  
Old 12-26-2013, 04:43 AM
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GWIZ GWIZ is offline
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Originally Posted by cutter View Post

1. This is the waste. Notice how much it curls and bows because the chisel inserts itself into the aluminum & spreads it so the scrap has to have somewhere to go.
It "bunches up" on both sides of the cut.
By placing the bevel side of the chisel in towards the waste you can force most of the distortion inwards, leaving you less cleanup on the hole.

Also notice the marks left in the sacrificial masonite that I used to back the cutting.
You're going to need something dense enough to support your work but not so hard as to ruin the chisel.
That is just in case you want to use the chisel at full width some other time just regrind.
1) the remedy would be remove the center first. drilling three 1/4" holes should do it.

As for backing a piece of oak wood, the thicker the better.

As for grinding the width of the chisels, don't grind the full side length, the depth is less then 1/16" so that is all you need
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  #84  
Old 12-26-2013, 12:59 PM
Al 2 Al 2 is offline
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Not exactly what the OP wants to know for this current project. By chance I came across this on You Tube. Some may find it interesting. Once on You Tube it leads to other videos and another one of them is 'Drilling a square hole' Look here: http://www.youtube.com/watch?v=7n1r5XfVkyk
Al
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  #85  
Old 12-31-2013, 04:48 PM
johnyradio johnyradio is offline
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Quote:
Originally Posted by Al 2 View Post
I came across this on You Tube. ...'Drilling a square hole'
http://www.youtube.com/watch?v=7n1r5XfVkyk
yes, i've already drooled over that thing, it looks amazing. they are wobble or rotary broaches.

http://www.buybroaches.com/How-Broac...orks_ep_7.html

would love to use that, but too expensive: $50 bucks for a broach, plus $750 for a broach holder, plus the lathe, mill, or CNC machine to mount it on. Making it prolly the single most expensive option in this thread

(that said, i bet some DIY'er will someday DIY a hand-driven wobble broach for a fraction of the cost! But it won't be me)

For this project, i'm going for a very low-cost manual method, suitable for our youth fabricators (and suitable for our minimal non-profit budget). it looks like i am closing in on a method to cut any size/shape hole in aluminum, clean and burrless, with a tool costing about $10, including blades. Just waiting for the blades to be delivered. i will post the results here.

thanks!

Last edited by johnyradio; 12-31-2013 at 04:58 PM.
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  #86  
Old 12-31-2013, 05:45 PM
BukitCase BukitCase is offline
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An actual, honest-to-God D-sub punch would be the most idiot-proof, quickest and easiest way - but you're right, there's no way you're gonna do that for 10 bucks a pop. Best I can offer is good luck... Steve

(We all get stuck in that infamous triangle - the "good, fast, cheap" one - pick ANY TWO, you can NEVER have ALL THREE )
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  #87  
Old 12-31-2013, 06:10 PM
johnyradio johnyradio is offline
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Quote:
Originally Posted by BukitCase View Post
An actual, honest-to-God D-sub punch would be the most idiot-proof, quickest and easiest way - but you're right, there's no way you're gonna do that for 10 bucks a pop. Best I can offer is good luck... Steve
check out the thread if you have a chance. We've looked at the D-sub punch, which can cost in the range of $200.

You'll see the solution we're moving toward.
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  #88  
Old 01-12-2014, 01:16 PM
johnyradio johnyradio is offline
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the .028 spiral coping blades arrived, and they provide greater control and tighter turns than the .040 blade.

Later when i get the same .028 blades made for a jeweler's saw, i expect that will give even better control.

As far as i'm concerned, this thread is solved!

But would really appreciate these loose ends:

The workpiece will be clamped to the edge of a table with a quick clamp. i'm thinking to use some cloth or foam, to prevent the aluminum from getting marred by the clamp.

this process does generate metal filings, so i need to work out a setup to safely catch/remove them, keeping in mind that our bench is often temporary, in a classroom or carpeted area. Maybe i can just put a trash bin on the floor under the workpiece.

i found that a wet paper towel easily wipes away filings that collect on the workpiece itself.

and need to find the best way to smooth the edges. There are no burrs, just a slight roughness to the edge. So i'm guessing a very fine grit, flat-face file, with a handle to protect kids fingers.

re the best way to stroke, i found this: "turn my file around and draw it back towards me. I think thats called draw filing and it works really well with the edges of skins. 2-3 pulls, light pressure".

i'm looking at the following el cheapo files, but i can't tell their grade. Any thoughts?

http://r.ebay.com/vBJkU4

http://www.harborfreight.com/12-piec...-set-4614.html

Last edited by johnyradio; 01-12-2014 at 03:14 PM.
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  #89  
Old 04-02-2014, 08:23 PM
johnyradio johnyradio is offline
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Quote:
Originally Posted by GWIZ View Post
7/16" hole.
what nibbler make/model did you use for this? the nibbler i tried is so big, i don't think it could do what you show in your pix. It looks like this:

http://r.ebay.com/jCo6JC
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  #90  
Old 04-03-2014, 06:14 AM
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Roundrocktom Roundrocktom is offline
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I use a Klein Tools Nibbler

Klein Tools 76011B Nibbler Tool

http://www.amazon.com/Klein-Tools-76...ywords=nibbler
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