Straight Tube Cuts

[smstachwick]

“Get some straight cuts! Get some straight cuts!”

Joking aside, when I cut my body tubes down to size, especially for booster stages but also for coupler repairs like the one I’m doing for my Hi-Flier XL, I’ve found that getting them cut in a straight line all around the tube is impossible with my current technique. Typically I’ll mark all the way around the tube as best I can with a pencil, make shallow passes with my knife until the tube falls apart, then sand down the last fractions of an inch to smoothness, sculpting it as best I can. Try as I may, however, I can never get the end of the tube exactly square all the way around.

Are there any specific tools or methods that I can use to make my rockets look a bit neater when I have to cut a tube?

 

[jmasterj]

I use several wraps of masking tape and then follow that around with my knife. I've wanted to try metal hose clamps but haven't gotten around to it.

 

[Blast it Tom!]

View attachment 519722
“Get some straight cuts! Get some straight cuts!”

Joking aside, when I cut my body tubes down to size, especially for booster stages but also for coupler repairs like the one I’m doing for my Hi-Flier XL, I’ve found that getting them cut in a straight line all around the tube is impossible with my current technique. Typically I’ll mark all the way around the tube as best I can with a pencil, make shallow passes with my knife until the tube falls apart, then sand down the last fractions of an inch to smoothness, sculpting it as best I can. Try as I may, however, I can never get the end of the tube exactly square all the way around.

Are there any specific tools or methods that I can use to make my rockets look a bit neater when I have to cut a tube?

I can't @ the guy, but JS Antares has mentioned a tubing cutter he uses. I am trying much the same, to make almost invisible parting lines between tube sections to fool my grandkids with @hcmbanjo's marvelous "Breakaway" kit. He cut them pretty clean, then I soaked the ends in CA and carefully sanded against a known right angle - very gently. If I ever get time I hope to do a build thread, but I haven't got to the paint stage to let you know how it turned out.

 

[lakeroadster]

I cut them 1/8" too long, then true them up on my Ryobi Belt / Disc Sander. It's an outstanding tool for Model Rocketry.

 

[smstachwick]

I cut them 1/8" too long, then true them up on my Ryobi Belt / Disc Sander. It's an outstanding tool for Model Rocketry.

I had one of those, many years ago. I think that got downsized when we moved.

I might end up trying @jmasterj ’s masking tape idea, I have plenty of that lying around.

 

[kalsow]

When my cuts aren't perfect, I stand farther away!

 

[tsmith1315]

All you need to do is get a sharp blade clamped firmly to something at the right height.

Pic below was for cutting a switchband. The plywood blocks were stacked to the height I wanted for the band. A razor blade on top and the whole thing clamped to the bench. Just a couple mm of the razor blade tip protruding.

Then hold the tube down and twist it against the blade.

 

[Blast it Tom!]

All you need to do is get a sharp blade clamped firmly to something at the right height.

Pic below was for cutting a switchband. The plywood blocks were stacked to the height I wanted for the band. A razor blade on top and the whole thing clamped to the bench. Just a couple mm of the razor blade tip protruding.

Then hold the tube down and twist it against the blade.

View attachment 519724

That's a really good idea, but I never do my own clamping. I always let my brother Jed clamp it.

 

[rharshberger]

View attachment 519722
“Get some straight cuts! Get some straight cuts!”

Joking aside, when I cut my body tubes down to size, especially for booster stages but also for coupler repairs like the one I’m doing for my Hi-Flier XL, I’ve found that getting them cut in a straight line all around the tube is impossible with my current technique. Typically I’ll mark all the way around the tube as best I can with a pencil, make shallow passes with my knife until the tube falls apart, then sand down the last fractions of an inch to smoothness, sculpting it as best I can. Try as I may, however, I can never get the end of the tube exactly square all the way around.

Are there any specific tools or methods that I can use to make my rockets look a bit neater when I have to cut a tube?

Build or buy yourself a Kuhn style tube cutter. If you have access to wood working tools a Kuhn cutter is easy to make, if not Apogee apparently sells one.

https://www.apogeerockets.com/Building-Supplies/Tools/Kuhn-Tube-Cutter
Get straight and clean cuts, by using a sacrificial coupler on the inside of the tube being cut especially larger diameter airframes. I have used my larger version of the Kuhn cutter on upto 3" Estes airframes, for larger airframes (and heavier duty Loc tubes) a pipe marking wrap works nicely with an exacto to start the cut then a heavier razor knife to finish it.

 

[smstachwick]

Build or buy yourself a Kuhn style tube cutter. If you have access to wood working tools a Kuhn cutter is easy to make, if not Apogee apparently sells one.

https://www.apogeerockets.com/Building-Supplies/Tools/Kuhn-Tube-Cutter

Interesting.

I’m going to have to make some investments in the workshop, apparently.

 

[prfesser]

I use several wraps of masking tape and then follow that around with my knife. I've wanted to try metal hose clamps but haven't gotten around to it.

Instead of masking tape I use the heavy cardstock that those mail advertisements for windows, Republicans, Democrats, whatever, that come in the mail. Wrap tightly around the tube to be cut, tape in place. It usually takes several wraps (the more the better). That provides a stouter guide against which the knife blade can rest. If the blade cuts into the guide that's usually not a problem because the guide is so thick, the blade doesn't cut through all the layers of the guide.

Sand afterward, checking as to whether the cut is square with a good carpenter's square.w

Best,
Terry

 

[DaHabes]

These for Estes tubes...https://estesrockets.com/product/002315-tube-cutting-guides/

This for LOC, Blue Tube fiberglass (and plywood fins)...https://www.acmetools.com/12-in-sliding-compound-miter-saw-dws779/885911450706.html

 

[Blast it Tom!]

Build or buy yourself a Kuhn style tube cutter. If you have access to wood working tools a Kuhn cutter is easy to make, if not Apogee apparently sells one.

https://www.apogeerockets.com/Building-Supplies/Tools/Kuhn-Tube-Cutter
Get straight and clean cuts, by using a sacrificial coupler on the inside of the tube being cut especially larger diameter airframes. I have used my larger version of the Kuhn cutter on upto 3" Estes airframes, for larger airframes (and heavier duty Loc tubes) a pipe marking wrap works nicely with an exacto to start the cut then a heavier razor knife to finish it.

Wow! JS Antares had mentioned it, but I didn't know Apogee sold it. I already have plenty of those clamps, all I need is a right angle and a scale and done!

 

[rharshberger]

Wow! JS Antares had mentioned it, but I didn't know Apogee sold it. I already have plenty of those clamps, all I need is a right angle and a scale and done!

use a razor saw to cut the slot for the blade, mine is made from 3/4" baltic birch.

 

[kuririn]

Kuhn tube cutter and a sanding block.
https://www.rocketryforum.com/threads/goonies.159406/#post-1998347

 

[Hobie1dog]

All you need to do is get a sharp blade clamped firmly to something at the right height.

Pic below was for cutting a switchband. The plywood blocks were stacked to the height I wanted for the band. A razor blade on top and the whole thing clamped to the bench. Just a couple mm of the razor blade tip protruding.

Then hold the tube down and twist it against the blade.

View attachment 519724

Genius

 

[neil_w]

Instead of masking tape I use the heavy cardstock that those mail advertisements for windows, Republicans, Democrats, whatever, that come in the mail. Wrap tightly around the tube to be cut, tape in place. It usually takes several wraps (the more the better).

That’s what I do, although I find two wraps is plenty.

Actually I use the Estes tube cutters (yellow plastic things) which work great for the tube sizes they support.

 

[JoePfeiffer]

Some sort of jig is key. I use a piece of angle aluminum in my bench vise, with a pair of vise-grips holding another piece as a stop at the right length.. put the time in the first angle up against the stop, hold the knife against the end to position it, rotate the tube.

 

[cwbullet]

These for Estes tubes...https://estesrockets.com/product/002315-tube-cutting-guides/

This for LOC, Blue Tube fiberglass (and plywood fins)...https://www.acmetools.com/12-in-sliding-compound-miter-saw-dws779/885911450706.html

I use this multi-material double complex miter saw for large tubes.

 

[rharshberger]

I use this multi-material double complex miter saw for large tubes.

Its a compound miter saw with a special blade that can cut steel, the average power miter saw (compound miter or regular miter) with a standard carbide blade will cut most rocketry materials except steel.

 

[cwbullet]

Its a compound miter saw with a special blade that can cut steel, the average power miter saw (compound miter or regular miter) with a standard carbide blade will cut most rocketry materials except steel.

But at that price, I added a carbide blade and I can use it for both.

 

[lakeroadster]

Its a compound miter saw with a special blade that can cut steel, the average power miter saw (compound miter or regular miter) with a standard carbide blade will cut most rocketry materials except steel.

I've got a power miter saw. Are you saying you've used a power miter saw to cut 1.64 cardboard LPR tubing?

 

[Paul Howard]

Here's the "light unit" construction and installation I made for a night flyer. I got several of these cool LED light strings from eRockets.biz (the Ohio fun kids who run Semroc). The battery pack used 2 common CR-2032 batteries. I made the body tube cutting jig awhile ago from wood sitting around. I used a BT-50 tube for the housing and installed a used 24mm D12-3 casing under the cut-line while cutting for a better cut. The shiny silver is self-adhesive material sold at most hobby shops. Anyhow, hopefully my tube-cutting jig makes sense by the pictures, hope this is of some use.

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[gb1113]

A universal fence clamp (Rockler Item # 31373) might work well for the clamp block instead of a hand clamp as shown. Light weight and low profile - and they work for hold downs for jigs too.

 

[SDramstad]

All you need to do is get a sharp blade clamped firmly to something at the right height.

Pic below was for cutting a switchband. The plywood blocks were stacked to the height I wanted for the band. A razor blade on top and the whole thing clamped to the bench. Just a couple mm of the razor blade tip protruding.

Then hold the tube down and twist it against the blade.

View attachment 519724

That works well assuming the end of the tube on the bench is also square.

 

[eugenefl]

I've got a power miter saw. Are you saying you've used a power miter saw to cut 1.64 cardboard LPR tubing?

I recently used my 12" Dewalt miter saw with a "DIABLO 80-Tooth Fine Finish Circular Saw Blade" to cut 3" mailing tubes and it was a thing of beauty for the thick walled cardboard. My curiosity led me to try with something much smaller and thinner - a BT50 (.976) tube. While the cut was 90deg, the edge was too rough for my liking despite moving the blade slowly. I had to use thin CyA on the edge and then sanded the rough cut smooth. Given the choice between trying to correct squiggly lines and "frayed" edge due to first/second/third blade passes with the Exacto, I'd actually try the miter saw again.

I've been on the fence on the Estes circle tube cutters. My main concern is a new blade catching an edge of plastic and gouging the material. I'd pay more for a more durable edge to ride a blade against.

I like the razor jigs and the suggestion to cut down leaving an 1/8" then sanding on a belt/disc sander. Always wanted one of those....hmm, heading to Harbor Freight tomorrow. Might have an extra tool to also support the woodworking hobby.

 

[teepot]

I use a compound Miter saw. Newish fine finish carbide tipped blade. From 24mm to 4". With blue tube it's a dream. When I've used a razor saw, a coping saw, a hack saw or exacto it never comes out square no matter how carful I am.

 

[rharshberger]

I use a compound Miter saw. Newish fine finish carbide tipped blade. From 24mm to 4". With blue tube it's a dream. When I've used a razor saw, a coping saw, a hack saw or exacto it never comes out square no matter how carful I am.

But with a compound and or sliding miter saw in the larger sizes and harder materials, careful of feed rate or the blade can deflect a small amount making a not square cut, talking about blue tube, FG, and large cardboard airframes. For bigger stuff over 4", I use a jig in my tablesaw that allows the tube to be butted against the fence and rolled around to complete the cut. No pictures of the table saw jig as its a quick and easy one to make from whatever is available in the shop (scrap wood) at the time.

 

[teepot]

I'm aware of that phenomenon. Learned the hard way. I go very slow. Always mindful of where my fingers are. I look where they are before turning on the saw.

 

[neil_w]

I've been on the fence on the Estes circle tube cutters. My main concern is a new blade catching an edge of plastic and gouging the material. I'd pay more for a more durable edge to ride a blade against.

This is something to be careful about, but after a few tries I got the feel for the angle to hold the blade, and the amount of pressure to apply, that it is no longer a problem.

Although the plastic is definitely not the most durable, it *is* extremely slick, and is therefore good for both sliding on the tubes, and providing a friction-free surface to turn against the blade.

They have worked well for me. But when cutting BT50H, BT70, or BT80, I use the cardstock-wrap method.