Cut tube ends

Joshua F Thomas

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So I've started cutting tubes for my first scratch built. The tube cutting rings are very helpful, and the cuts are very good. Just not *exactly* good.

How should I get the ends to match up as closely as possible? Just sand the ends down until they match?
 

rharshberger

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So I've started cutting tubes for my first scratch built. The tube cutting rings are very helpful, and the cuts are very good. Just not *exactly* good.

How should I get the ends to match up as closely as possible? Just sand the ends down until they match?
Connect temporarily with a coupler mark the high section and gently sand using a sanding block till you feel it looks right, then test fit and repeat of necessary.
 

David Schwantz

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Kind of like Rich said, but I use a belt sander with the guide to hold it in place. Little at a time and keep checking fit as you go. I also have a sheet of sand paper glued to a board that is screwed to the bench. You can use this and do it by hand, I use an orbital motion and keep turning it as one hand is stronger than the other.
 

neil_w

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What size tube are we talking about? For LPR tubes I stick a coupler in and sand on a sanding block. If it's an end of a tube that will not be glued to anything, then I'll give it a good CA coating before sanding.

Getting clean tube cuts takes practice. Try varying the angle of the blade against the tube.
 

Joshua F Thomas

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What size tube are we talking about? For LPR tubes I stick a coupler in and sand on a sanding block. If it's an end of a tube that will not be glued to anything, then I'll give it a good CA coating before sanding.

BT-70
 

Funkworks

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I like to work as manually as possible, so for a 5.38" tube, I:

- drew 8 marks around the diameter, to see the right length from any viewpoint
- joined the marks with masking tape
- set the tube on a typical cradle
- held a utility blade against the tube and the masking tape with the back end of the knife against the table top with hand A,
- spun the tube about 10-20 times with hand B, such that the blade followed its own cut, but cutting deeper each time.

A little sanding and it made it as a straight a back end as I could possibly want.
 

Hooked On Rockets

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So if you are talking about making true edges to match up with which each other, you could do this:

IMG_2134.JPG

Glue up some sandpaper to a FACTORY EDGE body tube with CA and then cut out the sand paper inside the tube with an exacto...
then use a body tube coupler inserted in the rig to true up the cut edge.
And of course, since it looks like you have cut a BT shorter than factory, you should have a factory edge on your "cutoff"....that's the edge you wanna glue up to the sand paper.
 

Aeronerd

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So if you are talking about making true edges to match up with which each other, you could do this:

View attachment 424979

Glue up some sandpaper to a FACTORY EDGE body tube with CA and then cut out the sand paper inside the tube with an exacto...
then use a body tube coupler inserted in the rig to true up the cut edge.
And of course, since it looks like you have cut a BT shorter than factory, you should have a factory edge on your "cutoff"....that's the edge you wanna glue up to the sand paper.
Super idea!
 

caveduck

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hmm this just gave me a great idea for some 3D printed widgets...all you need is a coupler-sized cylinder with a flange on it and a way to cut sandpaper rings (maybe make it 2 parts with coupler and flange separate).
 

neil_w

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I just tried making a couple of these and affixing and cutting the sandpaper is a bit tricky. How do you cut that clean circle out of the middle?

I also realized that my tube cuts have gotten so good that I don’t really need this, but it’s still too cool not to try.
 

neil_w

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hmm this just gave me a great idea for some 3D printed widgets...all you need is a coupler-sized cylinder with a flange on it and a way to cut sandpaper rings (maybe make it 2 parts with coupler and flange separate).
That could be an excellent item... cutting the sandpaper is the hard part I think.
 

Joshua F Thomas

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So if you are talking about making true edges to match up with which each other, you could do this:

View attachment 424979

Glue up some sandpaper to a FACTORY EDGE body tube with CA and then cut out the sand paper inside the tube with an exacto...
then use a body tube coupler inserted in the rig to true up the cut edge.
And of course, since it looks like you have cut a BT shorter than factory, you should have a factory edge on your "cutoff"....that's the edge you wanna glue up to the sand paper.

Wonderfully clever idea! Thanks!
 

neil_w

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If I understand this very-clever idea correctly...one could glue a sheet of sandpaper to a stock coupler. Set coupler on a flat surface, slide tube over it, rotate back n forth. No need to cut out a circle.
This could work as well, but the incredible appeal of the suggested method is that you just rotate the two tubes against each other in your hands, so you don't have to work to keep it flat against the sandpaper.
 

neil_w

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OK, here we go.

I glued the tube to 220 grit sandpaper (seemed like a good choice for this) by applying a nice bead of medium CA around the joint. Pro tip: give it plenty of time to fully cure.
Tube sander-2.jpg
I then carved the hole out with a #11 Xacto. Turned out to be pretty easy job, only took a minute. The harding of the tube/paper joint from the CA made it pretty easy to remove only sandpaper and not damage the tube (not that small nicks will make any difference).
Tube sander-1.jpg
Of course I had to test it out. Insert coupler halfway...
Tube sander-3.jpg
Then insert tube to be sanded...
Tube sander-4.jpg
Then twist the two tubes against each other. Worked great! Will need to knock the lip off the edge of the tube when finished, but that's super easy.

I made a BT55 and BT60 so far, with a BT50 in progress. Bonus: they nest nicely for storage!
Tube sander-5.jpg
I rate this as an A+ tip.

Now if only I had ordered a BT-70 coupler in my last order...
 

Joshua F Thomas

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I tried this today with a BT-70 tube and 220 grit and I'm not particularly impressed.... I still have a visible gap on my tube ends after sanding.

109069035_319909222523429_8145398455485496317_n.jpg

109862897_1166318687055522_2643029542413581490_n.jpg
 

neil_w

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1) Sand off the lip on each piece
2) If the tubes are going to be glued, then there's nothing to be concerned about anyway. Just use some filler to smooth the joint.
3) If they *are* going to be glued, do some more sanding. :)
 

mooffle

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That's a cool technique with the sandpaper on the end of the coupled tube.
My go to is just rough cut and then sand with a 320 grit block. The key is circular motions. If you try to go back and forth you'll end up skewed almost every time. Going in circles means you introduce the slant evenly, making it average out to completely flat. Hope that makes sense.

Sanding is 90% of my builds...
 

prfesser

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I tried this today with a BT-70 tube and 220 grit and I'm not particularly impressed.... I still have a visible gap on my tube ends after sanding.

You want to try to remove the burr that's sticking out on each tube. That may be the reason they don't fit together. Try sanding the edges of each tube very lightly with finer sandpaper, holding the sandpaper in a curve at about a 45 degree angle, and stroking only toward the center of the airframe (don't saw back and forth).
 

neil_w

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Just did some tube cutting over the last couple of days. One additional tip: if you wrap the cut edge with cardstock or something before sanding the edge (using whatever method), it'll prevent the splayed-out lip you usually get. Seems obvious in hindsight.

I cut some BT70, and since Estes doesn't have a tube cutting guide that size, I did my usual and wrapped a piece of cardstock around the tube as my guide. Then I left it in place and sanded the top off with a sanding block (easier with large tubes). Came out perfect with very little effort, no lip.
 
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