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May 20, 2019, 09:09 PM
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Question

Uniform balsa thickness reduction


RCGroups,
I have the need to very uniformly reduce 1/4" and 3/16" balsa sheets from .010 to .030" from as delivered dimension.
I have large perfectly flat 3.5" x 11" sanding blocks that can thin it down......but the uniform thickness is NOT occurring due to varying hardness of the balsa stock. Is there a method to thin the balsa uniformly using only hand tools I need to be aware of?

Any guidance or pointing me in the right direction is appreciated. Thanks much.

Bruce in Austin
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May 21, 2019, 04:48 AM
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AA5BY's Avatar
Bruce, could you affix some steel rails on either side to establish the the thickness? Perhaps easiest is to find a friend with a planer.

I have a stash of rough cut balsa and thickness mill it using a planer.
May 21, 2019, 07:15 AM
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epoxyearl's Avatar
Be very careful of 'standard' planers.. Those knurled drive drums can imprint your balsa with the mark of doom ! (Experienced loser).

A guy in our club made a sanding fixture to use on his 6" belt sander, but he's no longer with us.. He had purchased a lot of Balsa that was tapered from 1/4 to 3/16" edge to edge that needed leveling off..

I don't think there's an 'easy' way. His method was a pair of smooth rollers fastened above the belt sander, adjusted to hold the balsa in contact with the spinning belt. I'm not sure how 'accurate' it was , but there was a lot of dust, to be sure.

I'd be interested in a great solution, as well.
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May 21, 2019, 08:47 AM
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Quote:
Originally Posted by AA5BY
Bruce, could you affix some steel rails on either side to establish the the thickness? Perhaps easiest is to find a friend with a planer.

I have a stash of rough cut balsa and thickness mill it using a planer.
Using music wire as guides on the sides of the balsa sheets should work for keeping your sanding flat. That is going to be a lot of sanding when you consider the size of the flat surface. Perhaps a belt sander would help. I have used the music wire trick for making tapered ailerons out of flat stock.
May 21, 2019, 08:54 AM
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epoxyearl's Avatar
Bruce- How'd you get yourself in that position, anyway ?

I'm curious as to what you're doing..
The music wire / spacer thing is a good idea, and maybe you could space the balsa up with stacked paper shims to reach your goal ?
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May 21, 2019, 09:06 AM
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The worst $450 you can spend IMO but they do sell a LOT of this high cost miniature crap tooling

https://www.micromark.com/MicroLux-D...ickness-Sander
May 21, 2019, 10:40 AM
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epoxyearl's Avatar
Roger S. bought their table saw.
I have NEVER seen a table saw with no side play in the shaft..... The Micro saw has none. absolutely no side play.
The wood leaves the saw as if it's been sanded after cutting.
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May 21, 2019, 01:33 PM
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Quote:
Originally Posted by Fredvon4
The worst $450 you can spend IMO but they do sell a LOT of this high cost miniature crap tooling

https://www.micromark.com/MicroLux-D...ickness-Sander
Seems like maybe you could make a sander like that. A 2" drum 6" wide turned by a motor on a flat surface and set at the thickness you want and push the wood through. Hmmmmm naw... belt sander and push the wood through. you can rent a belt sander.
May 21, 2019, 01:55 PM
AndyKunz's Avatar
Quote:
Originally Posted by Fredvon4
The worst $450 you can spend IMO but they do sell a LOT of this high cost miniature crap tooling
"Serious" commercial woodworking thickness planers stop about 5/32" thick.

This looks to be a decent tool for the job.

Andy
May 21, 2019, 02:15 PM
B for Bruce
BMatthews's Avatar
Quote:
Originally Posted by epoxyearl
Roger S. bought their table saw.
I have NEVER seen a table saw with no side play in the shaft..... The Micro saw has none. absolutely no side play.
The wood leaves the saw as if it's been sanded after cutting.
Any good quality cabinet maker's table saw would not be a "good quality cabinet maker's saw" if it had any play in the blade shaft bearings. So they are out there. But they are not the cheap "construction saws" for the most part.

To thickness the balsa using only hand tools is going to require sanding it down. And I'd say that the way to do this is a flat bench or "tray" with raised guides and a very wide sanding block where you can move the block with sandpaper on part of the face along in a "WWWWWWWWWWW" motion side to side along the length of the pass. This will cut rapidly while also clearing the dust to avoid clogging the sandpaper. But it means a heavy thick sanding block to avoid flexing and it also means a longer block and wider spaced thicknessing guides to allow for the side to side motion. Sandpaper only on middle portion and "wings" that ride on the thicknessing guide rails. The block could be something like a well flattened 2x4 or two layers of 3/4" plywood. And you'll need to trap the balsa with fences to stop it moving around. And check frequently to ensure dust does not "pump" it's way under the balsa and lift it up.

I'd go with 80 grit for the roughing and finish with a light 120 along the grain to remove the last couple of thou and give a nice finish.

Another thing to watch for is that you'll "stretch" the wood on the side being sanded if you use a lot of pressure. I learned this years ago when I sanded down balsa for indoor duration models from 1/32 to 1/64 and even thinner in some cases. So use good fresh sandpaper and switch it frequently and light pressure on the block so it floats over the wood and let the grit do the work.

I also found that good ol' open coat garnet works best on balsa. It has the very sharp razor like edges that cut the wood instead of bulldozing it like some other papers do. Although the new "high performance" sandpapers also are doing a great job in this respect. And they last well too.

At the balsa mills this sort of work is done with a thickness sander...... and a VERY strong and effective dust collection package.
May 21, 2019, 03:31 PM
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Norm Furutani's Avatar
I use the attached two devices in a drill press. On the left is a Wagner Safe-T-Planer and is good for hard balsa and other woods. It will chew up soft balsa. On the right is a home made, cast aluminum, disc sander. Very good for reducing the thickness of balsa. You might be able to reproduce this tool from plywood and a threaded bolt for a shaft. Both are used for doing exactly what you want to accomplish.


Norm
May 21, 2019, 04:14 PM
Registered User
Thread OP

Guys, thanks for the ideas.......


........and suggestions. Because I need to do this so seldom, I won't invest much to get it done. My drill press is only semi-accurate as it is needing some "new and Improved" non-Chinese spindle bearings....lol. BUT.....since it is balsa I'm trying to massage to tolerance....I may not experience any run out. This idea I will try and I appreciate your input and any further comments or ideas you guys have.

Sincerely,
Bruce in Austin
May 21, 2019, 05:35 PM
Bellanca Kruesair
epoxyearl's Avatar
I like Norms' idea. I'll probably make one of those, just 'because'.

I've been force feeding large , built Balsa parts across my Belt Sander to get them 'roughed in, before block sanding.

I can see using a fence, and making several passes across the drill press table for perfectly flat parts. Thank you.

Bruce needs perfect tolerances , and this could be the answer.
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May 21, 2019, 06:43 PM
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Norm Furutani's Avatar
For balsa, I do recommend using only the sander. The planers tend to tear balsa. I think a very usable one could be made from two 3/4" pieces of plywood glued together. Epoxy or screw in a 1/2" shaft. True the face by running it against a piece of sandpaper. Because I'm trying to remove stock, I usually have 60 or 80 grit paper on the face of the sander.



Whether the sander or planer, this is the technique I use- https://www.bing.com/videos/search?q...5&&FORM=VRDGAR


Here's another video using a fence-
StewMac Safe-T-Planer Video (3 min 57 sec)



Norm
May 21, 2019, 07:41 PM
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AA5BY's Avatar
I've come to sense that I've been fortunate with the ability to plane balsa. It could be blade sharpness has something to do with it or perhaps the cutting speed of the particular planer.

My planer is a Hitachi and does a good job. In fact, my old Sears belt drive joiner produces a good surface as does a hollow ground planer blade when cutting sticks from a plank that has been planed.

Minimum height on the planer is just over 1/8" but I've had no problem piggy backing sheets and milling 1/16" x 4" sheeting.

This 28% Fly Baby that I finished yesterday, had all the balsa milled via the joiner, planer, band saw, and hollow ground planer blade.


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