# Fin cutting

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#### JStarStar

##### Well-Known Member
TRF Supporter
I admit it, I am a balsa butcher.

Anything with a straight edge, I am fine with a razor saw, but as far as freehand cutting with a knife, I am hopeless. Hack City.

And that's on standard hobby balsa... I haven't even made the leap to basswood or plywood yet.

What's the best way to cut that stuff? A scroll saw?

Ebay has an imported Electro-Lux mini-jigsaw that looks like it might be good. What about centering rings, elliptical fins, intricately notched TTW fins, etc?

I know we have a lot of woodworking wizards here, I am just trolling for ideas.

#### wwattles

##### Well-Known Member
I've done centering rings quite nicely with a flycutter. I've seen both bandsaw and scroll saw fins, tubes, etc., but never done any myself.

WW

#### powderburner

##### Well-Known Member
JStarStar, when you say 'freehand' do you literally mean with no cutting guide at all?
I cut balsa all the time using a cheapo school ruler with the little metal strip inset into the edge. I position the ruler over the 'good' side of the cut (the side where the part is/will be), line up the metal ruler edge with the line to be cut, and make several light cuts with an Exacto. I don't try to cut all the way through with one cut. If I screw up and the blade wanders away from the ruler, then it cuts up on the 'waste' side of the line (the side that will not be included in the final part). This works just fine for balsa fins and other parts that have straight edges.
For curved edges, sometimes it is just better to cut well outside the curved line, stack the cut balsa parts using some of the straight sides as indicators, clamp them together and use a sanding block to finish them to the correct edge line.
If it helps your confidence, you can cut the parts a hair oversize (1/32 to 1/16 inch) on all sides, even on trapezoidal fins, and sand them down to final shape later.

#### rocketsonly

##### Well-Known Member
A bandsaw works very also.

#### Stymye

##### Well-Known Member
If your using an exacto type knife it can get tricky depending on which way the grain is running , cutting across the grain usually takes a few more passes with the blade , if your cutting at an angle to the grain, it helps to go against the grain otherwise your blade can wander and even pull out slivers of balsa from the edge as you cut.

when cutting curves your almost always going to have a rough edge so as powder mentioned , it's best to leave some material for sanding

I've cut alot of balsa and still mess up now and than , I often forget to keep the blade straight up and end up cutting the edges on an angle, resulting in more sanding

the best advice is to use a sharp blade and cut the balsa using light pressure, and as mentioned, use a straight edge whenever possible.

any type of saw blade is going to tear the edges up
and is way overkill for balsa fins, but is nice to have for plywood and thicker basswood fins

#### JStarStar

##### Well-Known Member
TRF Supporter
Powderburner, anything with a straight edge, I either use a razor saw, or a heavy-duty X-acto knife with a flat stainless steel ruler as a cutting guide. But I still seem to just hack up the balsa every time I use a knife, especially cutting across the grain as stymye says. I do, obviously, always try to cut outside the lines, and figure I can go back and sand off the excess.

Scroll saws seem like a good idea. You can get a decent one for $30-$50 on e-bay, and when you see the kind of designs the real scroll-saw gurus are able to do, obviously you can make almost any kind of cut you want with it.

I'm just trying to get a handle on what everyone thinks is the best option. I'm thinking of maybe taking the leap of starting to build some MPR/HPR stuff, and you need more than just basic balsa for that.

What we need is somebody to invent a computer laser-cutting unit, that you would hook up with a USB port, feed the balsa or basswood in like paper, that would die-cut the parts right off the computer.....

#### rkt2k1

##### Well-Known Member
What we need is somebody to invent a computer laser-cutting unit, that you would hook up with a USB port, feed the balsa or basswood in like paper, that would die-cut the parts right off the computer..... [/B]
Check out the following: Versa Laser

It's very cool, but at $10k, it's on the pricey side! #### jflis ##### Well-Known Member Originally posted by JStarStar What we need is somebody to invent a computer laser-cutting unit, that you would hook up with a USB port, feed the balsa or basswood in like paper, that would die-cut the parts right off the computer..... Yep, and that's what the folks who offer laser cut fins and rings use.... Works just like a printer. In fact many little shops are set up during the holidays to use these laser cutters to etch glass and tiles as gifts. cool stuff #### JStarStar ##### Well-Known Member TRF Supporter Originally posted by rkt2k1 Check out the following: Versa Laser It's very cool, but at$10k, it's on the pricey side!

Yeah, I think I'll spend $40 or$50 on a scroll saw instead!!

Remember, though - computers used to be $5,000 each, DVD players used to be$2,000 each, etc etc.

#### jflis

##### Well-Known Member
Originally posted by JStarStar
Remember, though - computers used to be $5,000 each, DVD players used to be$2,000 each, etc etc.
$5,000?? Heck, I come from the day where$5,000 wouldn't even purchase a 16K core stack (that's 0.016MB).....

A low end computer was in the neighborhood of \$150,000 - half a mil...

#### powderburner

##### Well-Known Member
Do you remember the Olivetti-Underwood "Programma 101" computer? It was the size of a (big) suitcase, had a teeny little paper-strip printout, and would accommodate a few hundred lines of machine language programming. We had one of those things in school, and played Olivetti roulette during study halls.

#### DynaSoar

##### Well-Known Member
Originally posted by JStarStar
I admit it, I am a balsa butcher.
...
What's the best way to cut that stuff? A scroll saw?
I'm pretty bad at it too. Basswood is actually easier, but still not easy for me.

What I've learned to do is, mark the wood, use a metal straight edge to cut against, hold it VERY tight so cutting doesn't make the straight edge slide, and make the cut several times, a little at a time. 1/8" basswood usually takes about 5 cuts.

I usually don't try to cut curves. I cut only straight edges and sand down to the drawn line.

#### edwardw

##### Well-Known Member
I don't have any power cutting equipment so here is how I cut my fins. I take a good metal straight edge off a square. Once I have my pattern traced onto the balsa I put the metal straight edge so it covers the line. Then I clamp that down to my benchy with a piece of wood underneath it. I have a very fine toothed wood pull saw. You can bend the blade at 90 degrees and cut still, very flexible. (I use it at work for cutting out sill plates and trimming stuff overhead) I keep the blade tight against the wood and start slowly. Once I've got a groove in there it's good to go. Nice easy cut. I just square off any rounded portions pretty close. Then I start with some 60 grit sandpaper and shape everything that way. Once I get the shape I take out the 200 and finish it.

For centering rings I have two fly cutters, one set for outside and one for inside. I love them. Works really nicely.

Edward

#### DynaSoar

##### Well-Known Member
Originally posted by DynaSoar
I'm pretty bad at it too. Basswood is actually easier, but still not easy for me.

What I've learned to do is, mark the wood, use a metal straight edge to cut against, hold it VERY tight so cutting doesn't make the straight edge slide, and make the cut several times, a little at a time. 1/8" basswood usually takes about 5 cuts.

I usually don't try to cut curves. I cut only straight edges and sand down to the drawn line.
duh.

I fergot. I use an Xacto.

One thing I have found, the blade tries to follow the grain. If you're not cutting exactly along the grain, the blade will tend to go off the line in the direction of the grain. The thicker or denser the wood, the more it tries. I've learned to "lean" against the grain when I cut, applying a little lateral pressure to prevent this.