Jig for cutting nose cones into tail cones

[BDB]

I am hoping to build a 6” dia rocket using Blue Tube for my L3 certification attempt. The design is a 150% upscale of a Binder Design Velociraptor.

One of the key steps will be converting a PML Pinnacle nose cone into a tail cone. I think I’ll need to build a jig to hold the cone while I cut it with a miter saw. Has anyone built something like this before? I already have some ideas for how to do it, but I wouldn’t mind seeing other jigs so I’m not reinventing the wheel.

 

[fyrwrxz]

Oh boy! This has been sorely needed for a long time! With the advent of 3d printing and all the wizzos here, this should be a snap. No, I'm not going to buy a 3d printer. Not that dedicated and way too lazy to find another learning curve to climb. Bought my oldest a very nice one and he paid me back by moving to Seattle. Some people's children, eh?

 

[ThirstyBarbarian]

Maybe you can ask around what they use at a nose-to-tail restaurant.

 

[BDB]

I have a 3D printer and one of my ideas for the project uses it. In essence, I could print a series of progressively smaller rings to support the NC. The key would be to mount them on a board and get the whole thing to fit into my power miter saw.

 

[ThirstyBarbarian]

Maybe instead of rings, print a few squares with different-sized holes. You could make the squares a bit bigger than the diameter of the cone — say 7” or so for a 6” cone. You could print one for the shoulder end with holes that the shoulder will fit through. Then print a few for the pointy end with different sized smaller holes — maybe one with a 1” hole to fit near the tip, one with a hole a bit smaller than the diameter where the cut will be, and one a bit bigger than where the cut will be. That way you get both ends supported, and also support on either side close to the cut. Making them square would give you even support on the table, and also on the fence (or whatever that is called — not very familiar with these tools).

 

[lakeroadster]

Seems like 2 pieces of plywood, with round holes would do the trick. Make the cut so the boat tail is too long, so you can sand it to size.

 

[David_Stack]

Could you not simply temporarily secure the nose cone to be cut to a length of body tube, and then support the body tube in a set of V-blocks so that the tube is parallel to the saw table, and perpendicular to the blade?

 

[OverTheTop]

I would be wary of using a 3D print for a tailcone. They can be brittle and the rocket comes down tail first.

My Velocirapror is my most-flown rocket.
https://forum.ausrocketry.com/viewtopic.php?f=6&t=1782

 

[David Schwantz]

Damn, and all I do is cut them on my bandsaw by hand. god, I gotta git more modern

 

[rharshberger]

Damn, and all I do is cut them on my bandsaw by hand. god, I gotta git more modern

I mark them using two different but appropriate sized centering rings with spacers. to mark where I want it, then cut slightly long with a bandsaw (metal or wood depending on nc material, then using a Dremel 543 bring it back to the marked line.

 

[fyrwrxz]

Maybe you can ask around what they use at a nose-to-tail restaurant.

Oh dude! I have a hilarious story about the infamous Vandenberg crew's Bbq's. Not fit for TRF. pm me if interested.

 

[BDB]

So here's my first crack at a 3D printed jig. I combined Thirsty and Lakeroadster's square idea with my idea of 3D printed concentric circles. It was pretty easy to draw up a 7" x 7" x 18" block with a cone-shaped hole in the middle. The cone has a 6" diameter cylinder at the base to accommodate the shoulder of the NC. I then removed 2" thick slices from the block to leave six 1" thick blocks with centered holes. I'll try to print a few of the slices to see how they could work. Then I'll need to figure out a way to mount them to a base.

Please feel free to give feedback.

Here's to over-engineering!!!

 

[jmasterj]

A cone-shaped hole won't quite fit an ogive NC unless you've over-sized it, which seems to defeat the purpose.

 

[BDB]

A cone-shaped hole won't quite fit an ogive NC unless you've over-sized it, which seems to defeat the purpose.

You are right. I don't have the CAD skills to match the ogive shape. My goal is to generate a series of concentric circles. Hopefully, I can place them along a wooden base to support the nosecone. Because of the differences between the conical and ogive shape, they won't be evenly spaced.

 

[rharshberger]

So here's my first crack at a 3D printed jig. I combined Thirsty and Lakeroadster's square idea with my idea of 3D printed concentric circles. It was pretty easy to draw up a 7" x 7" x 18" block with a cone-shaped hole in the middle. The cone has a 6" diameter cylinder at the base to accommodate the shoulder of the NC. I then removed 2" thick slices from the block to leave six 1" thick blocks with centered holes. I'll try to print a few of the slices to see how they could work. Then I'll need to figure out a way to mount them to a base.

Please feel free to give feedback.

Here's to over-engineering!!!

View attachment 530374View attachment 530375

Put wooden or aluminum rods in the bottom two corners (through holes like rails), then the panels can slide to where you need them, if the dowels are wood or aluminum they will not hurt the saw cutting boattail if you accidentally hit them.

 

[BDB]

Put wooden or aluminum rods in the bottom two corners (through holes like rails), then the panels can slide to where you need them, if the dowels are wood or aluminum they will not hurt the saw cutting boattail if you accidentally hit them.

I was just thinking about something like that. Here's the mock-up with 1/4" rods. I could even use threaded rods with 1/4-20 nuts to hold everything in place. If everything is secure, I may leave one of the rods out to accommodate the blade.

 

[jmasterj]

You are right. I don't have the CAD skills to match the ogive shape. My goal is to generate a series of concentric circles. Hopefully, I can place them along a wooden base to support the nosecone. Because of the differences between the conical and ogive shape, they won't be evenly spaced.

Good point. They'll fit somewhere!

 

[cls]

How about a lathe?

 

[OverTheTop]

How about a lathe?

That's what I would use, but I am lucky enough to own one. I would fit my dental drill (slow speed, 180kprm) with a burr in the toolpost holder. Makes a nice job of cutting circular stuff that way.

 

[rharshberger]

I was just thinking about something like that. Here's the mock-up with 1/4" rods. I could even use threaded rods with 1/4-20 nuts to hold everything in place. If everything is secure, I may leave one of the rods out to accommodate the blade.
View attachment 530382

actually just pull the two upper rods back as far as needed to clear the blade, if you are cutting a NC tip off, then the blade should be clear of the lower two rods. If just pulling one rod (upper side closest to blade) will work then so much the better.

 

[James Duffy]

How about a lathe?

That would work. See this post for more detail.

 

[OverTheTop]

If you are going to use a lathe be careful with a parting tool. Very easy to have it jag in and rip the NC out of the chuck. You could use a Dremel with a cutoff wheel resting on the toolpost. Better job and safer.

[edit] I have been known to hold a small angle grinder in the same situation. It works.

 

[Glasspack]

BDB,

It worked great for mine........ Attached the nose cone firmly to a section of 4" body tube with a known good clean straight edge.
I used a jig made from heavy particle board (you can use any good wood) basically two pieces at a prefect 90 degree angle !

Secure the assembly to the jig and cut it with my Miter radial Arm Saw. Hold it all firmly and let the blade cut so you don't
push the cone down and make the cut less than square. This is the final cut "After" shot

 

[bwayne64]

You are right. I don't have the CAD skills to match the ogive shape. My goal is to generate a series of concentric circles. Hopefully, I can place them along a wooden base to support the nosecone. Because of the differences between the conical and ogive shape, they won't be evenly spaced.

If you want to match the ogive, cut a piece of cardboard to match the shape and scan it on a scanner. Your cad software should have a background image or tracing function. Use that to draw the profile in cad. Then lathe it out, ; )

 

[Gramparocket]

I put the cones in a body tube tape it in place. set it on the saw and cut with light pressure so you don't push down on the cones while cutting

 

[ThirstyBarbarian]

I know I suggested the 3D printed squares with holes, but I’m thinking the guys who are securing the cone in a length of tube and then cutting it with light pressure probably have the easiest method.

 

[rharshberger]

I know I suggested the 3D printed squares with holes, but I’m thinking the guys who are securing the cone in a length of tube and then cutting it with light pressure probably have the easiest method.

I like the lathe method best, instead of fully cutting through score it 90% then finish with a razor knife, should make for a nice perpendicular to axis cut aka "square"....on a round tube....

 

[heada]

Lathe is best. Set it up with a steady rest and then hit it with a parting tool. No muss, no fuss. Take less than 30 min to do.

Next best would be pieces of plywood to make a cradle to hold it level and then run it through the bandsaw/tablesaw. I wouldn't use hand tools or a dremel to cut it because then you're asking for it to be uneven or have it grab and tossed across the shop.

 

[ThirstyBarbarian]

I like the lathe method best, instead of fully cutting through score it 90% then finish with a razor knife, should make for a nice perpendicular to axis cut aka "square"....on a round tube....

I’m sure a lathe is the most accurate, but not everyone has access to a lathe. I think the OP has a power miter saw. Maybe he has a lathe too.

I had a custom rocket kit with a cut and slotted tail cone made for me by LOC. They used some kind of CNC for that. That’s what we all really need!

 

[BDB]

One would certainly get a "square" cut using a lathe, assuming you could carefully mount the 6" nosecone in the chuck. Unfortunately, I don't have a lathe, so that option is out.

I have thought a lot about inserting the NC into a body tube and holding it against the fence of my miter saw. That might work better for a radial arm saw with a large footprint as Glasspack described. My miter saw looks something like this, so it doesn't have a large fence to support a 6" x ~18" nosecone that has been inserted into a length of body tube. I would need to build an extension for my fence, but I suppose that is possible.