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Maplehead

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#1
Good morning All

I want to take a .5” by .5” by 3” long bar and cut one long side so that it has two sides at 120 degrees. This is so I can then cover the angled sides in high grit sandpaper and sand a 120 degree groove. (I’ve searched for an existing 120 degree file to no avail.)
I imagine I would afix the bar in my vice but it would lay on some complementary angled piece, (60 degrees?), and then cut one angled side at a time.
If this is the simplest approach, how would I do this? Those angle blocks don’t look like the right pproach, but maybe they are?
 

Reddinr

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#2
I wonder if you could use adhesive to glue two 60 degree files together. That might not make a clean angle at the bottom of your groove but if that is not needed, maybe it would work.
 

Maplehead

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#3
I wonder if you could use adhesive to glue two 60 degree files together. That might not make a clean angle at the bottom of your groove but if that is not needed, maybe it would work.
Interesting. However, for me the most important part of the angles is where they meet. I need that sharp.
 

Mitch Alsup

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#4
At 3" long, you could angle the milling head 30º and simply cut both sides of the bar; leaving you with a 120º angle and a fairly sharp edge.

On the other hand, if you can do the above, you probably don't need to make a tool and use sandpaper, you can mill the end product directly.
 

rock_breaker

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#5
Mitch Alsup has the easiest answer my $0.02 would be to hold it securely, perhaps 2 bolts through a holding plate into blind holes in your bar. The plate would be clamped to your mill table.
Ray
 

francist

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#6
At 1/2 X 1/2 X 3" long for a sanding block I think I would just drop the table on the disc sander 30degrees and dust off two corners on the working edge until they meet in the middle. Even in steel it wouldn't take but a minute. In aluminum, even faster.
If you're using cold rolled bar, be prepared for a bit of spring when the one side comes off. Might make it a bit banana-shaped.

-frank
 

Maplehead

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#7
At 3" long, you could angle the milling head 30º and simply cut both sides of the bar; leaving you with a 120º angle and a fairly sharp edge.

On the other hand, if you can do the above, you probably don't need to make a tool and use sandpaper, you can mill the end product directly.
Fixed mill column.
 

Maplehead

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#10
At 1/2 X 1/2 X 3" long for a sanding block I think I would just drop the table on the disc sander 30degrees and dust off two corners on the working edge until they meet in the middle. Even in steel it wouldn't take but a minute. In aluminum, even faster.
If you're using cold rolled bar, be prepared for a bit of spring when the one side comes off. Might make it a bit banana-shaped.

-frank
Hi Frank, I don’t get what you’re meaning but it does sound like my most doable option. Can you clarify for this novice?
 

francist

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#11
Does this make it clearer? I'm assuming you have a disc sander for your woodworking, so by dropping the table 30 degrees off 90 you could take half the width of one face off from two opposing sides of your 1/2 X 1/2 block and end up with a 120 degree ridge in the centre. Like this:

image.png

-frank
 

Maplehead

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#12
Does this make it clearer? I'm assuming you have a disc sander for your woodworking, so by dropping the table 30 degrees off 90 you could take half the width of one face off from two opposing sides of your 1/2 X 1/2 block and end up with a 120 degree ridge in the centre. Like this:

View attachment 277549

-frank
Before you replied here I got your idea but what I did was make a 30 degree wood wedge to use for the metal piece.
Now, with your drawing clearly stating what you meant, I am incredibly embarassed to say that yes, I do have that sander, yes, it does swivel with degree markings, and no, I didn’t even know that. Lol
 

WarrenP

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#13
Remember your sander markings probably aren't perfectly accurate. Better check the angles.
 
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