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My tube cutting, uh, "jig"

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neil_w

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Had this idea yesterday and tried it out tonight.

I use the Estes tube cutting guides for everything up to BT60, but don't have the equivalent for BT80, and my previous freehand attempts have been pretty frustrating. So, basing off my vague understanding of how the Kuhn tube cutter works, I rigged up this:
ImageUploadedByRocketry Forum1477531783.920966.jpg

That is an Exacto knife held in a vise. Underneath are a couple of shelves to prop up the tube, and a piece of waxed paper to provide a smooth, non scratching surface.

To use, I held the tube against the blade and rotated it toward me like so:
ImageUploadedByRocketry Forum1477531961.014063.jpg

It actually worked pretty well, especially considering it was my first try with it. I found that, contrary to when I hold the knife in my hand, I could apply quite a bit of pressure and cut the whole tube in about two passes. Here's my result:
ImageUploadedByRocketry Forum1477532090.177321.jpg

Like I said, not bad for my first try. A bit of sanding and it's all cleaned up.

When finished the entire setup is broken down and put away in about 30 seconds. Total cost: $0.

Pretty ghetto, but I'll call it a success.
 

Peter Olivola

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Using a piece of paper wrapped around the tube to align things and then masking tape to keep it in place, it's easy enough to hand hold a razor knife, making multiple light cuts, to get a really good, clean tube cut.
 

Micromeister

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Years ago I had exactly the same problem. Just not likeing the way tube cutting was going with both A-acto blades or Razor blades.
So I invented the Tube Annilator 42000. Made of scrap aluminum angle and bar stock I had laying around the basement. I believe the entire cost ended up at less then 10 bucks including the #24 X-Acto blade.
But the turely important addition was the discovering that CLEAN cutting body tubes REQUIRE an internal mandrel to get that Factory Clean edge.
The mandrel does not have to be as long as the tube but must be wide enough to support the tube in the area being cut. This little 19" long fixture works on tubes from 1/8" diameter to BT-101. See the photos below to see the mandrels I've found and made for each size body tube. and the pdf drawing of the Tube Annilator 42000. Hope this stuff helps a bit.

Cutter-f2a_Tube Anniliator 42000 Decals Bt-50_06-24-08.JPG


View attachment Tube Annihilator-42000-a_Section & views Dwg_02-25-10.pdf
 

pythonrock

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Don't use wax paper. As you rotate the tube, some of the wax can rub onto the tube and the paint will never stick
 

neil_w

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Using a piece of paper wrapped around the tube to align things and then masking tape to keep it in place, it's easy enough to hand hold a razor knife, making multiple light cuts, to get a really good, clean tube cut.
In my experience thus far (admittedly limited compared to others around here) the combination of hand-holding the blade, keeping it aimed correctly, and applying consistent pressure is troublesome for me. Holding the tube against a fixed blade was a lot easier for me.

But the truely important addition was the discovering that CLEAN cutting body tubes REQUIRE an internal mandrel to get that Factory Clean edge.
I had a piece of coupler inside the tube I was cutting, which maybe is not as good as a mandrel but at least supported the tube while cutting.

This little 19" long fixture works on tubes from 1/8" diameter to BT-101. See the photos below to see the mandrels I've found and made for each size body tube. and the pdf drawing of the Tube Annilator 42000. Hope this stuff helps a bit.
Very nice. I'm sure I'll incrementally improve mine as I go. I already have a couple more ideas just to hold the tube in position more consistently.

Don't use wax paper. As you rotate the tube, some of the wax can rub onto the tube and the paint will never stick
Now that is a good point, I will retire that wax paper pronto.
 

hcmbanjo

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One thing I've learned with tube cutter rig (doing kit production, I've cut a LOT of tubes)
Use just the very tip of the knife blade, or corner of the square edge of the razor blade.
I use single edge razor blades on my cutter. A lot cheaper than #11 X-Actos.

I first thought using the middle of the cutting blade would work better, You know, more surface
on the tube. On a fluke, I used the square corner tip of the razor blade and got the cleanest, quickest cuts ever.

It helps to use an internal dowel or spent engine casing on thin wall BT-20 and BT-50s.
When you get up to BT-55s and 60s you can cut pretty well without inside support.
BT-70s and 80s don't cut as well on the jig I have. The tube you cut looks pretty big.
 

mccordmw

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I cut tubes using my sliding miter chop saw. Seems to work well for me. I've cut everything from 1" tubes up to 6" tubes; all paper LOC-style tubes. Haven't tried FG yet.
 
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