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  #1  
Old 06-20-2005, 10:05 PM
gaia gaia is offline
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Default how to cut weird angles?

I'm about to start on a project which requires me to cut square tubing at angles like 51, 63, 71, 79,109, etc. degrees.

That is the edge of the one tube should be 90 degrees while the other should for example be 71 degrees.

Is this possible with my cutoff saw or must I revert back to the old hand hacksaw.
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Old 06-20-2005, 10:33 PM
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I think it would be hard to hold that kind of tolerance with a cutoff saw. Plus if you're trying to mate two completely different angles there will be a slight problem. The mating surfaces will be a different length because of the different angles. The bigger the angle difference, the bigger the problem. Essentially the mating surfaces are the hypotenuse of a right triangle.
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Old 06-20-2005, 11:27 PM
bgott bgott is offline
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What are you trying to build?
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  #4  
Old 06-21-2005, 12:22 AM
JTMcC. JTMcC. is offline
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Quote:
Originally Posted by gaia
I'm about to start on a project which requires me to cut square tubing at angles like 51, 63, 71, 79,109, etc. degrees.

That is the edge of the one tube should be 90 degrees while the other should for example be 71 degrees.

Is this possible with my cutoff saw or must I revert back to the old hand hacksaw.

You'd be crazy to even think of using a hacksaw.

I also think it's crazy to try to mate pieces with different angles on the ends.


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Old 06-21-2005, 04:26 PM
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Hi gaia, I agree with the others, mating different angles like this, seem as they never look right. The best you can hope for is to place the very best welds you can. This will impress the less knowing people out there. They will be concentrating on the quality of the weld, and not the fit. Whenever I have to cut really oddball angle cuts, I like to use my Port-a-band saw. What I do, is scribe the top of the box tube, and both sides. I start the cut in the upper corner closest to me; go half way down the vertical wall closest to me, at the same time cutting half way across the top. Then roll the saw up on the top and down the backside. Once both vertical walls have been cut I cut the remaining bottom. I personally hold 85 to 90 % of the saw’s weight at all times, never set the entire weight of the saw on the material being cut! HACK SAW, I have one of them somewhere.

http://www.weldingmart.com/Qstore/p000724.htm
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Old 06-21-2005, 04:34 PM
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I think I have a hack saw somewhere on the truck, but I refuse to look for it. Port-a-band is the way to go. I don't even drag the torch out for 4" pipe on down, and I wish the port-a-band would fit on the 6" pipe. I don't push on the port-a-band, just let its' own weight drag thru the metal.
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  #7  
Old 06-21-2005, 07:18 PM
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you could use a zip/slice wheel to cut the angles if the tubing isn't to thick .


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Old 06-21-2005, 07:40 PM
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Quote:
Originally Posted by Pile Buck
Hi gaia, I agree with the others, mating different angles like this, seem as they never look right. The best you can hope for is to place the very best welds you can. This will impress the less knowing people out there. They will be concentrating on the quality of the weld, and not the fit. Whenever I have to cut really oddball angle cuts, I like to use my Port-a-band saw. What I do, is scribe the top of the box tube, and both sides. I start the cut in the upper corner closest to me; go half way down the vertical wall closest to me, at the same time cutting half way across the top. Then roll the saw up on the top and down the backside. Once both vertical walls have been cut I cut the remaining bottom. I personally hold 85 to 90 % of the saw’s weight at all times, never set the entire weight of the saw on the material being cut! HACK SAW, I have one of them somewhere.

http://www.weldingmart.com/Qstore/p000724.htm
After the cut,,we had a big job years ago, with alot of compond angles,,and some of the fits were awfull,one pc being almost a half inch longer,because of the hypotonus,,The co told us weld and blend, it was all 309 for a heat treating ovens,,,long door sections,,,Lost my shirt on that one,,Made it up when the second furnace needed new dooors,,,they left ct. and went with every one else,,Just wondering if you had a trick? Thanks,Jack--PS They were all 2x2x1/4 angle,,,so that really threw it off,,there head engineer came to the shop,,,he drew it,,and he could not figure it out either,,,alll autocad...
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  #9  
Old 06-22-2005, 03:17 PM
gaia gaia is offline
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Quote:
The mating surfaces will be a different length because of the different angles.
That I completely forgot - tho learned it the hard way in the past.


Quote:
What are you trying to build?
Space frame chassis using 1 by 1 inch .06 inch mild steel square tubing.

Quote:
You'd be crazy to even think of using a hacksaw.


Quote:
you could use a zip/slice wheel to cut the angles if the tubing isn't to thick .
Considered using a stainless steel cutoff disc. Damn thing is so thin that I'm a bit hesitant to use it.

I do'nt know. I feel like sitting betw a rock and a hard place: I want to build the chassis but my time is so very limited and we are moving in the next 3 - 4 months. It's kinda of a make or break situation - if I do'nt start now I'll probably never do it.

Thank you guys for all your input.
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  #10  
Old 06-30-2005, 10:30 PM
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Walker Walker is offline
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The fix for the long/short hypotenuse is to cut both agles the same and 1/2 of the total angle desired. The same way you cut two 45*s to make a 90*. As far as anle accuracy I would mark it on the tubing using a sharpie, then jig/shim it in the cut off saw a little on the long side, then just use a 4 1/2" angle grinder with a sanding disk an trim to perfection.
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