Looking for best way to cut fins........

[Re-Bar Ricky]

Hello all - I am working on rebuilding a rocket that I lost for a couple of months in a tree at our launch site. When I finally recovered it the nose cone was fine but the tube was warped and fins falling off. Also, the motor was stuck in the motor mount so I destroyed it when trying to get the engine out. Anyways, I've got everything ready to rebuild it but I am stuck on the fins. I purchased some 1/8" balsa for the fins and I am having trouble getting it cut. Is there a better way to cut something that thick other than with an X-acto knife? What are your tools of the trade for thicker balsa?

 

[neil_w]

Medium-weight balsa cuts easily at 1/8”. If you’re having trouble, and you’re using a good fresh blade, then you might have a dense/hard piece.

In my experience, cutting hard balsa is frustrating and challenging. But I still do it with a knife (a larger snap-off, with which I can get good leverage), just do many passes and apply more pressure when I hit hard grains.

If you have a scale, weigh your balsa and see how dense it is. If it really is a very dense piece, it’s going to be hard work to cut, no way around it.

 

[dr wogz]

don't try to cut it in one go. make several passes.

also, a small saw, a razor saw or coping saw, even a hacksaw to make "rough shapes", then refine with sand paper & sanding block

 

[prfesser]

A steel ruler or other metal straightedge is good for keeping the blade where you want it, at least on straight cuts. It usually takes me several passes to cut through hard balsa.

 

[David Schwantz]

Amazon.com: ZONA - ZON35-550 35-550 Fine Razor Saw, 42 TPI.010-Inch Kerf, Blade Length 6-1/2-Inch, Cut Depth 1-3/16-Inch : Arts, Crafts & Sewing

 

[SharkWhisperer]

Amazon.com: ZONA - ZON35-550 35-550 Fine Razor Saw, 42 TPI.010-Inch Kerf, Blade Length 6-1/2-Inch, Cut Depth 1-3/16-Inch : Arts, Crafts & Sewing

Agree it's a great hobby saw. But consider spending another $2.50 and get a quality saw set (4 blades) from the same company. Same handle with interchangeable blades.

https://www.amazon.com/Zona-35-140-...d=1648416665&sprefix=razor+saw,aps,120&sr=8-2
Though it doesn't have the 42-tpi blade you're looking at, it has a 32-tpi blade that will be a slightly less-fine-cutting replacement (but that's still pretty fine!), but also a super-fine, super-thin 52-tpi blade that also makes really nice razor-like cuts in all hobbyist woods. And a keyhole and larger saber blade for plunge-cuts and more maneuverability than the long flat rectangular blades (both at 24-tpi).

But if you just want to do nice linear cuts with a decent general-purpose razor saw, the one David linked to is good quality and should work for many different applications/woods beyond balsa (basswood and ply come to mind).

Make sure you know whether it cuts on the push or pull motion, and appreciate that the finer the teething, the shallower the teeth (and cut depth), so the teeth will fill up with dust and need wiping off a little more frequently than a rougher-cutting blade.

Razor saws are great!!!

 

[David Schwantz]

Yup. I've got the multiblade one also, even comes with a keyhole blade. But I like the solid one piece ones better, IMHO.

 

[Hobie1dog]

Do you know of anybody that has a saw or some smaller power tools such as a jigsaw with a fine blade, or a smaller hobby table saw that would make nice cuts in the plywood without having to go out and purchase individual manual tools?

 

[Re-Bar Ricky]

This sheet of balsa is from Hobby Lobby so it's not the highest quality out there. And I'm cutting an odd shape, not straight lines. I'll start with a fresh blade and go from there. Thanks all!

 

[neil_w]

This sheet of balsa is from Hobby Lobby so it's not the highest quality out there. And I'm cutting an odd shape, not straight lines. I'll start with a fresh blade and go from there. Thanks all!

Hobby Lobby has plenty of perfectly satisfactory balsa (well, balsa supplies are bad right now, but in general). The key is to get the correct density; medium density balsa strikes the perfect balance between rigidity and weight and ease of use. I always bring my scale and weigh each piece until I find one within my target range (or as close to it as I can get. I will err on the denser side, but not too far). I use the table below, which I keep on my phone.

It is totally worth doing this, and you will only feel a little self-conscious.

Balsa sheets weight reference
Target 10-12 lb/ft^3

1/32 x 3 x 36: 9g - 11g

1/16 x 2 x 36: 12g - 15g
1/16 x 3 x 36: 18g - 22g
1/16 x 4 x 36: 24g - 29g

3/32 x 3 x 36: 27g - 33g
3/32 x 4 x 36: 36g - 43g

1/8 x 4 x 36: 48g - 58g

1/4 x 3/8 x 36: 9g - 11g
1/4 x 1/4 x 36: 6g - 7.5g
3/16 x 3/8 x 36: 6.5g - 8g

 

[bjphoenix]

The last fins I cut out of 3/32" and 1/8" I used a razor saw.
If the OP is cutting curves then it might be necessary to cut straight line segments and then sand to shape.

 

[Stewman]

Do you know of anybody that has a saw or some smaller power tools such as a jigsaw with a fine blade, or a smaller hobby table saw that would make nice cuts in the plywood without having to go out and purchase individual manual tools?

You might try Micro Mark. I have their mini table saw and it's great for balsa, basswood and thin plywood.

 

[BEC]

Do you know of anybody that has a saw or some smaller power tools such as a jigsaw with a fine blade, or a smaller hobby table saw that would make nice cuts in the plywood without having to go out and purchase individual manual tools?

I have one of these for that purpose: https://www.homedepot.com/p/Dremel-...Plastic-Laminates-and-Metal-MS20-01/203899883

 

[Hobie1dog]

I have one of these for that purpose: https://www.homedepot.com/p/Dremel-...Plastic-Laminates-and-Metal-MS20-01/203899883

I have never heard of that, but what a great idea, and super practical for rocketry. Thanks for posting up the link.

 

[Hobie1dog]

Look on your local Facebook Marketplace for a scroll saw. There are 4 in my area for less than $50

 

[jqavins]

Your thread title says "Looking for best way to cut fins". Good luck with that. I'm looking for the best barbeque sauce.

 

[lakeroadster]

I cut fins a little oversized on my scroll saw. Then stack them up, clamp them together and finish sand them on a combination belt / disc sander.

It works pretty great.

 

[Hobie1dog]

Have you looked on Marketplace for a scroll saw yet?

 

[dpower]

Use Excel brand #11 blades, I've found them to be sharper than X-Acto brand. And they're made in the US.

 

[BigMacDaddy]

Came up in a "Similar Thread" and only 1 month old so not so dead... I strongly recommend a hobby CNC for people cutting complex or curved shaped fins or doing lots of different scratch-built rockets. Cutting fins used to be one of my biggest headaches and now, with the CNC, it is only a minor headache (the sawdust mess and space it takes up - which is only a few square feet).

 

[jqavins]

How much does a good quality machine with decent features cost? In other words, a basic, relatively inexpensive machine, but not crap. One can do pretty well with a $10 to $15 coping saw, a file or two, and sand paper. (And the files are optional.)

 

[BigMacDaddy]

How much does a good quality machine with decent features cost? In other words, a basic, relatively inexpensive machine, but not crap. One can do pretty well with a $10 to $15 coping saw, a file or two, and sand paper. (And the files are optional.)

I got this unit which works quite well for 2mm plywood with a 2mm downcut bit -- I think it was $179 + $49 when I got it (the upgrade to the 3040 extension lets you easily cut 200x300mm sheets).

 

[jqavins]

A little pricey for me. I guess I'll have to, ahem, cope with simpler tools.

 

[BigMacDaddy]

A little pricey for me. I guess I'll have to, ahem, cope with simpler tools.

I just stopped buying kits and only buy raw materials now which saves some money

Kudos to the folks that scratch build these complex models without 3D printers and CNCs. I do not have those skills (or that patience)...

 

[G_T]

Are you by chance not using a fresh blade? #11 Xacto blades don't stay sharp long. I buy the 100 packs? The ones that are dark blue colored, from the tempering process. Not the silver ones.

Gerald

 

[BABAR]

Something outside the box that may help, especially since you apparently have some curves so a straight edge won’t work on all edges.

cut a template out of medium cardstock, heavy enough that you can confidently trace around it with a ballpoint pen.

use the template to trace your fin pattern on the balsa (make sure you get the grain direction right, don’t ask how I know this), not just once but several times, pressing the ballpoint a little harder each time into the wood. Because balsa is soft, you can get some pretty deep “trenches” with just the ballpoint. It won’t cut the wood for you, and you will still have to go slowly and carefully and make several passes, but it will help keep the knife “in the groove” a bit easier.

 

[bjphoenix]

I've been working mostly with the larger XActo handle, I think it uses a #2 blade. I was going to cut some tubes so I pulled out a new unused small handle, I think with #11 blade. I noticed that the blade seemed a lot thinner than the larger blade. I've had trouble with the larger blade trying to cut all the way through 3/32" and 1/8" balsa, next time I'm going to try the thinner #11 blade.

 

[Back_at_it]

If I'm cutting Balsa or Basswood I typically use with a sharp Xacto knife. For long straight edges I use a steel ruler and make multiple shallow cuts until I get though the media. For plywood I'm currently using a table top Scroll Saw.

Really need to get on buying that laser cutter.

 

[BigMacDaddy]

A little pricey for me. I guess I'll have to, ahem, cope with simpler tools.

I should have also said -- anyone in a CNC group would never say that is a good/decent machine with good/decent features but it works well for cutting fins from plywood.