PilotJunky

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Hi All...

When cutting balsa wood with a #11 Xacto blade I find that regardless of whether the blade is brand new, or how careful I am, the balsa tends to crush rather than cut (When going across the gain). I've tried multiple soft passes, and new blades but I'm not finding anything satisfactory. Are there any tried and true methods such as wetting the balsa or a technique I may be missing?

Thanks for your help.

David Cutler

Sometimes it's better to use a razor saw than a knife.

What thickness are you having problems with cutting?

-David C.

Red B.

Hi!

A sharp blade should be able to cut balsa without crushing it. Are you really using Xacto blades or some other inferior brand? There are definite differences in quality between different brands. IMHO the best scalpel blades are those made by [link=http://www.swann-morton.com/blades3.html]Swann-Morton[/link].

For best results the knife should be held at an angle of 30-40 deg. above horizontal in the direction of the cut. As you have noticed, cutting cross-grain is more difficult than cutting along the grain. Cross-grain cutting is best done in several shallow cuts.

I don't use scalpel blades very much for general cutting as I find them rather weak and "wobbly". My favourite knife is an ordinary Stanley knife that use Snap Off Blades. You will find these in any hardware store.

/Red B.

SoCal GliderGuider

Could be the balsa.

Rocketeer10

two suggestions, one is that I usually stack and cut ribs with my band saw instead of cutting with a knife. Even when only cutting two ribs at a time for tapered wings, I like to use my disc sander to sand them to shape after the saw.
two, if you carefully brak off the very tip of a hobby knife, it will cut better as the tip won't curve inder the pressure, perhaps this will help. If the balsa is too soft, make several ight passes with the blade to prevent crushing the grain.
Cheers,
GY

BMatthews

Sounds like soft balsa but a sharp knife should do a good job. I suspect like Red suggested that you're holding the knife too vertical. Lay it over to that angle so it tends to shear cut rather than plow cut.....

wrongwaywayne

Try using the one sided razor blades. They are much sharper than exacto. I also use them for covering. To get the exacto sharper you will have to hone on a wet stone, and then leather.

PilotJunky

My Feedback: (2)

I appreciate all of the responses...

The solution appears to be the angle at which I am holding the blade. As we all hold a pen differently, I suspect I was holding the Xacto knife at too great an angle. It feels a bit awkward... but I'm sure I'll adapt. I also used a piece of scrap balsa under the piece I was cutting such that the blade did not dull on a hard surface under the wood. It's now more cutting than crushing....

On to some scratch building

cltom

Don't hesitate to change blades often. You may need 2 or 3 just to cut out all the ribs for a wing. Also, I didn't see this mentioned in any of the thread, but thickness is important. There is a point where you must change from a blade to a saw. That's usually anything bigger than 1/8" thick for me. You can get get away with more than that for some sticks and a fresh blade - 1/4" spars, for instance, but a saw is still better.

SoCal GliderGuider

I've used a poking or "hidden line" type of cutting across the grain. Chiseling. Spent many years cutting ribs with #11. Best thing I did was to buy a band saw and belt sander. A scroll saw works too.

Stew99

It's almost impossible to make a really clean cross grain cut. For sticks I use a razor saw. For sheets I make multiple passes with an xacto knife. In either case I true up the cut with a mitre sander. For thicker material or curved cuts I use a jig saw and then sand with a disk or belt sander. If you're serious about building you will need a variety of sanders.

dicknadine

I have found that cutting the part oversize and then sanding to the proper size is the answer. makes no difference if your using a razor knife or saw, you have to sand to proper size. its like everything else in the hobby- you learn the best-- for you -- by trial and error. we have all gone thru this--there is NO SHORT CUT. dick

PilotJunky

My Feedback: (2)

All great advice... thank you.

I'm in a condo right now, so power tools are a limited option. I'm also building a small electric flier to start. Patience, Sand Paper, the right knife angle, and fresh blades all seem to help out. Being too much of a perfectionist can cause grief as well... after all, I'm not going to be getting in the thing :-)

Thanks again