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Old Jun 28, 2007, 02:26 AM
65stang is offline
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How to cut balsa parts???


This might be a stupid question but........... I have tried to cut balsa parts before, but every time I do they crack or break in some way. I use a nice new sharp blade to cut with, so am I doing something wrong? Is there a better way? Thanks for the response
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Old Jun 28, 2007, 02:27 AM
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Hello 65stang,

What blades are you using? What thickness of balsa?

Paul.
Old Jun 28, 2007, 02:36 AM
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Quote:
Originally Posted by pldaniels
Hello 65stang,

What blades are you using? What thickness of balsa?

Paul.
I am using the normal standard exacto-style blade and I was cutting from Midwest 1/16 balsa sheet.........although I might be cutting from 1/8 sheet in the future also.
Old Jun 28, 2007, 02:46 AM
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You are pushing too hard and breaking the balsa. Many light cuts are better than a couple of hard cuts.
Old Jun 28, 2007, 02:51 AM
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Quote:
Originally Posted by tomahawkflier
You are pushing too hard and breaking the balsa. Many light cuts are better than a couple of hard cuts.
I'll try that, thanks
Old Jun 28, 2007, 02:57 AM
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when you say it 'breaks', does is it breaking with the grain? 1/16" isn't very thick but if the balsa is 'C' type brain (mottled appearance) it'll have a tendency to split.

As tomahawkflier says, try a few lighter cuts.

For cross-grain cutting on thicker balsa, make sure you get a small razor saw.

Paul.

Paul.
Old Jun 28, 2007, 03:19 AM
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You might also want to try a single edge razor blade instead. They are a bit thinner than #11 blades and work better in some circumstances.
Old Jun 28, 2007, 08:05 AM
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Several gentle passes with the knife are better than trying to go all the way through at the first pass. Also, don't rush it.
Are there any local modellers you are friendly with who could watch what you are doing and give you advice? It is much easier to demonstrate than describe.
After a little practice you will wonder why it seemed so difficult.
Old Jun 28, 2007, 10:05 AM
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There are some tricks to cutting balsa with a blade. I’ve been doing this for more than half a century now and have it down pat.

• 1/8” thick is about the maximum you can cut with a blade. More than that usually needs a saw, preferably a jig or coping saw.

• Use single-edge razor blades which can be bought in boxes of 100 for about $6 from hardware stores. Razor blades seem (to me at least) to more easily follow the line you want to cut without wandering. Sometimes you need an X-acto knife with a no. 11 blade to get into tight spaces. If so, always use a new, sharp blade.

• ALWAYS cut the inside curves while the parts are in the whole balsa sheet. It’s the cutting of the inside curves that seem to break the cut-out pieces. Therefore cut these curves before you remove the part from the balsa sheet.

• On tight inside curves cut as best you can, then use a sanding stick (a piece of round wood dowel with some fine sandpaper glued to it) to sand up to the line. I have various sizes of wood dowel and flat sanding sticks I have made and accumulated over the years.

• Learn to enjoy the cutting and sanding process. Don’t hurry it along. Be precise. I guess this is the difference between a “builder” and a “flier”. The “builder” enjoys the building process, the “flier” just wants to get something in the air as fast as he can.

Planeman
Old Jun 28, 2007, 11:20 AM
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Planeman's tips are great. I cut parts out oversized with about 1/16" to 1/8" left to trim to the line of the part. Trying to cut to the line out of a sheet of balsa can be frustrating. Often, when cutting a notch in a rib or former, I'll see the wood split but I just glue it back together with a shot of CA or whatever glue is handy.
Old Jun 28, 2007, 09:03 PM
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always make sure the grain is running away from the part you are trying to cut as you cut, so if a split occurs, it is away from your part.

Sand any time you are not 100% sure you can cut without splitting. I always use sandpaper on a sanding stick for cutting spar notches - I actually have a ruler that when neatly wrapped with sandpaper is nearly exactly 1/8 inch, works perfectly for cutting 1/8 spar slots..
Old Jun 30, 2007, 11:31 AM
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Yep, take your time and make a few cuts instead of trying to cut it all the way through with one cut. I like the idea of cutting them a little bigger then sand to size. What I have found that makes a world of difference is the tool you cut with. I got on ebay and bought #3 scalpel handles and #11 blades, you wouldn't believe the improvement over hobby blades. And you don't have to stop all the time and tighten the blade up again.

"Z"
Old Sep 04, 2010, 05:06 PM
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Norm Abrams on New Yankee Workshop also cuts outside the line when using a bandsaw (also applies to jigsaw) and then sands down to the line. So this is an established woodworkers trick.


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