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Old Feb 05, 2013, 11:39 AM
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Joined May 2012
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Routers and Balsa

Ok, I don't like to sand. That said I've got endless sets of tail feathers, (OK maybe 25 sets - seriously) that will need to be radiused or beveled. I've sanded these things for years and I've got a nice Great Planes sanding bar but I do a lot of large scale furniture projects and if I want a full radius or a bevel or something fancier it goes on the router table and I get very good configuration control with very little sanding required. I am talking about a full radius really centered on the part not something that looks sort of full radius which may or may not be centered on the part

I've got two Dremel tools and a router table from Dremel that allegedly fits one or the other and I've got some high speed steel router bits for them. That said. I can see chewing through the elevator in a heart beat. For the straight edge, particularly an elevator with a dowel used to join the two panels I can set a cutter up flush with the fence and if I've got a beading bit center it up on the dowel and ... I guess I need to set up on some scrap pieces and try this out.

Anyone have some experience with this kind of an operation, source of fancier full radiused cutters?

Regards, Cliffc
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Old Feb 06, 2013, 03:30 PM
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Joined Apr 2012
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I've tried routing balsa wing ribs. Didn't work out too good. If the grain changes or the router is pushed a little too fast...BOOM... Shacker, Lacker, Lacker. Best thing was the debris wouldn't hurt you. Routing ribs was more trouble than it was worth. Even new bits were not sharp enough.

I did see a drum sander type bit for routers somewhere, but they were all straight sided. Looked promising for some operations.
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Old Feb 06, 2013, 07:31 PM
-insert witty saying here-
Hemikiller's Avatar
United States, CT, Killingworth
Joined Dec 2005
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I've used my full size router table to bevel and radius sheet balsa. Never had any real issues. It took 95% of the work out and the rest was a quick job with a sanding bar....
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Old Feb 06, 2013, 08:13 PM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
11,427 Posts
The softer and lighter the balsa the worse it cuts with stuff like routers I've found. As gwilliams said they just con't seem to be sharp enough to not catch and pull out fibers. Actually if working with a hand pushed plane on balsa is any indicator the fibers get pulled from the wood and fold over the edge and then you push a little harder and all hell breaks loose.
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Old Feb 06, 2013, 09:06 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
Joined Jul 2011
4,091 Posts
OK, so how do the CNC routers work when cutting balsa? I've heard some are using routers instead of a laser. Of course you don't hear about some of the issues so I may be talking out of turn.

Ken
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Old Feb 07, 2013, 05:56 AM
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Marysville, WA
Joined Oct 2008
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Even with a brand new bit on our CnC router it still shreds the edges of balsa parts from time to time. Seems the lighter and softer the balsa the worse the "fuzz" around the edges. Santa did leave us a new 40watt CO2 laser cutter for the shop, but that still wont help me round any edges over.
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Old Feb 07, 2013, 11:01 AM
You sabotaged my plane.
eliworm's Avatar
Arizona
Joined Jun 2002
2,806 Posts
How about trying a climb cut with the router. Works where needed on "normal" wood.
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Old Feb 07, 2013, 11:11 AM
AndyKunz's Avatar
Illinois
Joined Sep 2001
24,083 Posts
Has anybody ever wondered why the routed balsa LE on a Ringmaster kit is hard as oak? It's not because you want it to survive an in-tree landing ...

Andy
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Old Feb 07, 2013, 11:46 AM
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I tried a climbing cut on those ribs. Say you're are looking at a rib blank with the trailing edge pointing to six o'clock-leading edge pointing to 12 o'clock. Starting at the spar notch (thickest part of rib) I routed counter clockwise to the leading edge (twelve o'clock). Then starting at the spar notch again, I used a climbing cut to the trailing edge (six o'clock).

This gave better results than a counter clockwise cut all around, but still not acceptable.
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Old Feb 07, 2013, 01:50 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
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It's possible that some experimenting with the surface feet per second would help. Every material has an optimum speed for a cutting edge to pass by where it gives the cleanest cut. Balsa, especially the lighter density stuff, likely is different enough that it needs a higher or lower SFM of the cutting edge to get a clean cut. Or perhaps it needs specific face and back angles to the cutting faces to get a clean cut. It's a mistake to assume that router bit cutting angles intended for more normal woods will be optimum for soft balsa.

Just don't ask me what the angles or edge speeds should be. My own cutting is limited to how fast I can drag an XActo knife around...
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Old Feb 07, 2013, 02:07 PM
Pronounced "High Duck"
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Marysville, WA
Joined Oct 2008
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From my experience, there is really no "optimal" cutting speed/direction/rpm to router cut balsa. If the grain were always the same direction as every cut it wouldn't be a problem, but that's not practical. Eventually you will still need to cut across or with the grain. The best you can hope for is finding a cutting speed/direction/rpm that consistently reduces the amount of "fuzz" (and splitting) on the ends of the parts. I cut the ribs for this project with a CnC router using a 1/16" grout cutter bit. The "fuzz" at the ends of each rib wasn't too bad, but they still got sanded by hand.

I really don't see a way to completely eliminate sanding to round off the edges of balsa parts, but I'm sure there is a way. I'd love to hear about it.
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Old Feb 07, 2013, 02:52 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,411 Posts
My favorite tool for trimming down some balsa wood is the razor plane. They can be set for fine or coarse cut, and the shaving are easier to clean up than sanding dust.

This type of plane -


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Old Feb 07, 2013, 04:53 PM
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Illinois
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Can you find blades at the grocery store or do you need to get them on ebay?

Andy
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Old Feb 07, 2013, 09:41 PM
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Tucson, AZ, USA
Joined Nov 2000
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Just got a kit from RBC (Holland). All of the parts, ply and balsa appear to be routed with a 1mm cutter. Very clean and accurate with very smooth edges/cuts. Sure looks better than die crunching or burnt edges.
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Old Feb 08, 2013, 09:59 PM
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United States, AZ, Tucson
Joined Jun 2011
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I recently cut ribs for a CL-215 (76" wingspan) out of light balsa with a router. I use a 1/8" bit in a pin-guided router table using hard templates. I have found that the best way to get a clean cut is to climb cut first around the template and then go back around with a conventional cut to clean up the fuzz. The cutter length of a 1/8" bit limits the number of ribs that can be cut at one time; 1/2" length, so 4 to 8 ribs/parts at a time.
Plywood parts cut just fine with a conventional cut.
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