Quantcast

Cutting Body Tube

The Rocketry Forum

Help Support The Rocketry Forum:

danieljh14

Well-Known Member
Joined
Jan 29, 2009
Messages
87
Reaction score
1
I'm sure this is has been covered but I can't find it anywhere. Is there an easy way to cut body tube? I build low power stuff so the biggest body tube I will be using is BT-80. I have a razar saw and miter box that I use for small stuff but it isn't big enough to cut anything bigger then BT-50. Even with the miter box I have had problems with the body tube moving in the miter box so it doesn't cut straight. What am I doing wrong or is there a better/easier way to cut body tube?
 

powderburner

Well-Known Member
Joined
Jan 18, 2009
Messages
7,356
Reaction score
4
Hi Daniel,

Good qstn. I'm sure you know that there are lots of ways to do this and you are likely to get many answers.

When TRF1 gets back online you will be able to find tons of advice (and some great photo illustrations) on how to do this. Until then--

Mark carefully, use a sharp blade, cut slowly, and be careful not to add your fingers to the project. Mark carefully by using a clean new sheet of paper with a "factory" straight edge to wrap around the BT, and use a sharp pencil point to mark the circumference. (I suggest pencil because BIC pen markings can come back later to cause problems by ink soaking through the paint from behind.) Use the sharpest blade you can find, as in: this is definitely the time to use one of your brand new Xacto blades that you have been saving. Cut slowly and don't try to cut all the way through the BT on one pass--it may take you 3 or 4 or 7 times around the circumference before most of the BT is severed. And cut slowly and pay attention to keep the blade's cutting edge in the same cutting path, and not wandering back-n-forth all over the BT. Remember, to do the fastest overall job of cutting BT, you usually have to work slowly.

Other guys here on TRF have used hose clamp hardware to gently grip the BT and provide a guiding edge for the tip of your Xacto blade. This can work well too, but it requires a trip (or two) to the hardware store to find the right size clamp.

And if you are cutting very much BT, there are some very good illustrations of a fairly simple cutting jig that Micromeister has designed. My description would be a poor substitute for his pictures, so hopefully he will jump in here and share his photos again.
 

Micromeister

Micro Craftman/ClusterNut
TRF Lifetime Supporter
TRF Supporter
Joined
Jan 19, 2009
Messages
15,074
Reaction score
38
Location
Washington DC
As Powder mentioned lots of folks have had fine luck using steel hose clamps to gently squeeze the tube while cutting with a single edge razor blade or Shape X-acto blade. Key is the blade should be NEW, or stropped razor sharp.
It's also advisable if trying to cut tubing without an internal mandrel to try to do the cutting of the tube on the "PULL OUT" part of the blade stroke. This helps reduce the amount of damage to the interior of the tube.

I guess the most important "tip" I can pass along is to get really clean cuts on most Standard thickness and heavywalled Body tubes is to use an internal mandrel to backup the area under the knife blade. This is how the tube manufacturers do it. They have hard rubber expandable roller mandrels, We have to make do with spent motor casings, wooden dowels, PVC pipe, Heavy cardboard tube cores and built-up areas on these items with masking or Duct tape.
Driving a 1/2" down thru 13mm motor casings, 5/8" in 18mm and I believe 7/8" for 24mm casings you can sand and CA the exterors to make some great, very long lasting mandrels.
Once you have a set of internal mandels made they'll be around for a very long time.

Years ago I built an all Scrap aluminum cutting jig that works great but seems to been a little over the top for most folks;) The reason I chose aluminum angles to build this thing are First; The pieces involved are truely scrap I had laying around the shop. Second: Aluminum is stable, not tending to warp over time as wood parts have a tendency to do.
Others have used wooden corner angles or nailed or screw joined 1by angles for their jigs with fine results. The big thing is to have a way to adjust the depth of blade being used to cut into the tubes and some sort of adjustable stop to allow repeatable cuts. This can be as easy as an additional block of wood and a C-clamp. Again I'll stress the need for internal mandrels to really get factory quality, no sanding required tube cuts. I use my little 19" jig to cut all size tubing from under 1/8" to BT-101's (about 4").
Hope these pics will helps.

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

Zack Lau

Well-Known Member
Joined
Feb 13, 2009
Messages
538
Reaction score
0
I find that a body tube coupler works great as backing when cutting larger sized tubes. Instead of building a kit with several short tubes and couplers, I'll substitute a long tube and save the couplers and tubes for other uses.
 

peter_stanley

Well-Known Member
Joined
Apr 12, 2009
Messages
221
Reaction score
0
I cut a strip of card stock paper, and wrap around the tube, using the straight edge as a cutting guide. Once the wrap is perfectly aligned, I put a piece of masking tape on the wrap, and another piece to hold it to the tube. I use a fresh blade and rotate the tube while lightly scoring with the blade, keeping blade against the wrap edge. I continue this until the blade cuts through the tube. Once the tube is cut, take the wrap off, and light sand. It will be cleaner if the exposed part of the tube is the part being cut off, and not the part you keep. If I'm cutting a thicker tube I'll do the same thing, except use a razor saw instead of a razor blade.
 

judo

Well-Known Member
Joined
Jan 18, 2009
Messages
2,342
Reaction score
4
I used a cheap wooden version of something similiar to Micro. I got the idea from infocentral.org but their site is being referbed, or something.

PP45.JPG


PP46.JPG


PP47.JPG
 

El Cheapo

Well-Known Member
Joined
Jan 20, 2009
Messages
1,654
Reaction score
2
I cut a strip of card stock paper, and wrap around the tube, using the straight edge as a cutting guide. Once the wrap is perfectly aligned, I put a piece of masking tape on the wrap, and another piece to hold it to the tube. I use a fresh blade and rotate the tube while lightly scoring with the blade, keeping blade against the wrap edge. I continue this until the blade cuts through the tube. Once the tube is cut, take the wrap off, and light sand. It will be cleaner if the exposed part of the tube is the part being cut off, and not the part you keep. If I'm cutting a thicker tube I'll do the same thing, except use a razor saw instead of a razor blade.

Ditto....I've used this method very successfully on 2" x .125 mailing tubes which are alot thicker than most tubes.
 

RangerStl

Well-Known Member
Joined
Jan 17, 2009
Messages
1,080
Reaction score
1
Mine looks just like that as well. The only problem I have is that the end with the blade is not quite square... So if you don't hold the tube against the stop carefully, it will walk up the tube making a spiral rather than a square cut. And the mandrels are indeed a necessity.

Made the BT-80 mandrel out of an empty Testor's spray can wrapped with gobs of tape. :)
 

RimfireJim

Well-Known Member
Joined
Jan 20, 2009
Messages
988
Reaction score
0
Mine looks just like that as well. The only problem I have is that the end with the blade is not quite square... So if you don't hold the tube against the stop carefully, it will walk up the tube making a spiral rather than a square cut.
If you can't square up the end of the fixture, maybe you can square up the blade itself by putting a shim under one end of it. Depending on how out of whack it is, something like masking tape could work, allowing you to build it up in layers until you get the blade square. If multiple layers are needed, you can also make them in different lengths to get a tapered shim. Put the tape on the fixture, not the blade, so that when it comes time to replace the blade you're still all set.
 

RangerStl

Well-Known Member
Joined
Jan 17, 2009
Messages
1,080
Reaction score
1
RFJ;

That's probably the best solution. Now the inconvenience of the crooked end must win out over my laziness before I actually do something about it! :D

Thanks!
 

prowlerguy

Well-Known Member
Joined
Jan 18, 2009
Messages
419
Reaction score
0
My method is a little more low tech, but I haven't had any issues with it. I use an Estes tube marker to get a straight line around the tube. I then use that mark to guide the application of several wraps of masking tape, enough to make a significant guide. Then, like others have said, I make several passes with a new blade until I get through the thickness of the tube.
 

MarkH

---
Joined
Jan 18, 2009
Messages
1,073
Reaction score
2
Location
El Segundo
I ran some 2.6 inch aerotech tubes thru a table saw to get perfect cuts for some tube fins. Had to sand a little bit of fuzz off but that's about it. I know not everybody has a table saw but it worked like a charm.

TF01.jpg
 
Top