Turning Balsa

For those of you turning your own stuff, do you use a cutting tool or sand paper to get your shapes? I have a 80 year old guy here who is woodworker and asked him if he would teach me how to turn. When he asked what type of wood was I wanting to work with, he told me it was too light. I told him that you guys' were doing it, I just didn't know how, you were doing it. I suggested sandpaper maybe, and he said that he thought maybe I could do it like that. So, what do you guys' use?

Thanks for any input
Steve

Depending on how you plan to turn the wood, (assuming it's balsa) I glue heavy duty thin cardboard to both ends of the stock. This keeps the chuck and spindle end from chewing it up. At a simi-slow speed, you can tool the wood until you get it round. Then increase the speed for shaping. Once you get near the shape and size you are after, then you can rough sand to almost there, then graduate to finer grits to the finish. A few tools you will need is a parting tool, rough gouge, I like using a fingernail gouge also & a skew tool. You really don't have to buy a whole set/kit of tools because some dealers sell then separate. For a cheap learning set, you can get them at Harbor Freight.

Knock off the corners on square stock or glue lams. I use a spokeshave. Then wrap some aggressive sandpaper around a 12" file. Some balsa will have soft grain that tears with a regular gouge. Wear a mask- because there will be lots 'o' dust. Spray your face shield with anti-static fabric spray- It'll clean off later. Spin to rough and change out for final finishing. Don't load the paper or it will burn. I like using the open weave used by dry wall finishers. A shop vac really helps contain the mess. I cut the leg off a pair of pantyhose (your choice of colour!) and fit that around the filter to catch the really fine stuff. I just unchuck the turn and cut off each end with a draw saw. Be safe and have fun with your new creation!
(duh- I realized I was thinking of 3-5" and above diameters- I 'spose this works for really smaller ones too. Adjust your grit accordingly.)

I use sandpaper... wrap various grits around paint mixing sticks from the hardware store...

Start at about 36 grit to get the stock round (both balsa and pink closed cell house insulation foam that I've turned) and then switch to about 60 grit when getting closer to the actual size/shape desired...

You have to "sneak up on" the final size and shape, using progressively finer grits for the last quarter inch down to the final size and shape...

BTW, I use a simple electric drill mounted on a board for turning parts, with a hardwood dowel glued into the stock for a spindle... works fine, but you can't use too much pressure-- the dowel can't handle a lot of pressure on the piece...

Later! OL JR

Steve, you've asked a question that is going to give you a lot of different techniques and variables, which is good. You can decide what works best for you. Like fyrwrxz says, knocking the corners is a big plus. And you can still gouge on softer woods but do be careful when you do. I turned some cones with some awfully soft balsa before but I was careful. I would recommend buying some cheap 2x2's white pine or something to practice on first.

All the suggestions here are just what you do, nothing really I can add but... Learning on pine from that 80 year old wood worker is an opportunity you should not pass up. There's nothing wrong with a pine nosecone up to like 2.5", either. Many early high power rocket nosecones were made from other than balsa, basswood being another good choice. Later you can use this skill to turn larger cones from glued-up foam insulation. I looked like a blue snowman after even though I used a shopvac



edit: Thought I'd add my Conformation rocket used a 3.1" 5:1 Ogive pine nosecone just over 15" long with a 3" shoulder. It's got a sectioned together balsa one, now.

dave carver said:

Learning on pine from that 80 year old wood worker is an opportunity you should not pass up.

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Dave, I'm not 80 years old dood....LMAO!

Thanks for all the great advice guys. I'll give this all a go with Fritz as my instructor. Hopefully I'll have something respectable to show you.

I use xacto knives as gouges for small balsa parts. I wear a full face shield and use a light touch when turning with xacto blades. They work very well for balsa and basswood.

PM Gordy (aka sandman).

He does it for a living.

Greg

Not 80 years Old either but have been turning Balsa, Foam, Basswood and tons of "normal" hardwoods for many years.

As Gary and others have mentioned Balsa comes in a number of densities which help dictate what tools are used to turn it. Fyrwrxz's knock off the corners is particularly good advice for most balsa work.
As for tools: Really depends on the size and shape your trying to accomplish. Standard and Mini turning tools, chisels and gouges CAN be used once you have a bit of experience on setting up the lathe and work piece.
Adding Heavy cardstock to the ends and/or gluing in a hardwood dowel for the Chuck end really take all the fight out of keeping soft balsa and foam on the lathe.
Other have mentioned using sandpaper wrapped around files but neglected to tell you the Files work very well also.
I turn cones and transitions from .246" to BT-101 (just under 4") diameter using a combination of ALL these turning tools to get the job done, generally finishing with folded Sandpaper alone to smooth out the surface just before parting the piece.

Don't miss the opportunity to lean the tricks and tips your older friend has to share. I'm sure he has any number of really KEWL things he can show you on some scrap white pine

GregGleason said:

PM Gordy (aka sandman).

He does it for a living.

Greg

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I'm not sure how much help I could be. All the advise given so far is pretty much what I would say.

Figuring out how to mount balsa wood in the lathe is probably one of the hardest parts.
Small cones (BT-5 through BT-60) a glued in wood dowel works.*
Get good wood dowels! look for Made in U.S.A! The stuff from Taiwan or china WILL NOT WORK!!! It's crap!
Use oak or Poplar (Poplar is soft but better than the foreign stuff. Apparently the foreign trees aren't very good.)
Good hardwood dowels are available from Home Depot. Hobby lobby has the crappy stuff.

2" or larger balsa can be held on a 2" bowl plate.

Use a draw knife to knock off the corners.

Cut the piece to be turned a bit longer than needed and use the tail stock until the part is round.

I use regular lathe tools, don't use the scraper type lathe tools, those just don't work.

I have a water grinding stone next to my lathe and constantly sharpen. KEEP TOOLS SHARP!

After the part is round pull back the tail stock to get the tip.

I make sanding block out of scrap wood. Glue on 40 grit auto body sandpaper. The kind used for long boards. Make 100 grit and 220 grit blocks.

Final sanding finish is from 320 or 400 grit but use a very light touch.

DO NOT wrap the sandpaper around the part being turned! You will get an oval part, guaranteed!

Balsa has very uneven density. Usually it has a soft side and a hard side so it will sand unevenly with even steady pressure. You will become aware of the density change in the wood when you cut the corners off with the draw knife.

If you are going to do a lot of balsa turnings make sure you buy extra ON/OFF switches for your lathe. This is important because you will have to turn the lathe off to take measurements. A metal caliper can do a lot of damage to a spinning balsa nose cone.
There are just so many ON/OFF's in switch and with the constant On/Off cycles the switch will burn out faster than you think and it will happen suddenly.

Basically it's just not something you can really learn by reading. Sort of like learning to dance from a book.

You have to turn the music on (in this case a lathe) and practice, practice, practice.

You will ruin a lot of balsa learning but that's the cost I guess.

If there is one tool I find indispensable it would have to be my drill press. Not only is is essential for drilling holes perpendicular to a flat surface, it can also be used as a vertical axis lathe.

I build mostly scratch built rockets and have built quite a few nose cones with my trusty Ryobi bench top drill press. I start from a rectangular block of wood (balsa, basswood, straight grained pine, cedar or redwood) that has a square cross section. Next I mark the exact centers on each end by drawing diagonals. Then I use a pencil compass or plastic circle template and draw a circle on each end that is just a bit larger than the body tube of the project. Then I drill a pilot hole into one end to accept a short piece of hardwood dowel which is then glued in place and left overnight to cure. The hole depth will vary dependent upon the diameter of the finished nose cone and the length should be about twice the depth of the hole, leaving a short stub which can be chucked into the drill press as Luke Strawwalker suggested.

Before I actually start turning the workpiece I always shape it into an octagonal cross section with whatever hand tool seems to work best (hand plane, utility knife, whatever). I then chuck it up and start making sawdust, often by eye and sometimes by using a home made template. The key, especially with balsa, is to use light pressure. I usually start with a wood rasp, very gently, and progress using various grits of sandpaper and files. Like everything else there is a learning curve to this technique.

I've also had good results by plain old whittling and sanding. I find it time consuming yet strangely therapeutic. :wink:

I just turned two 54mm balsa nosecones on my metal lathe. After roughing in with the gouge, I used some steel wool to polish it. The wool cut better when I ran the lathe backwards. I think the three most important things are to use sharp tools and to sneak up on the final dimensions and a hard anchor point in the chuck.

Are there any tricks you guys use to get the shank back of the shoulder even or parallel? It seems I have difficulty in that area with too much removed at one end or the other and the nose cone wobbles in the body tube.


Richard

TheTellurian said:

Are there any tricks you guys use to get the shank back of the shoulder even or parallel? It seems I have difficulty in that area with too much removed at one end or the other and the nose cone wobbles in the body tube. Richard

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This is tricky for me at best. Balsa is easy to over sand and even the use of a good set of calipers, I can still screw em up. Usually I have to set my OD (which would be the same as the tube of course) just a wee bit larger. Maybe 1/32" on the calipers. Then once I can fit the calipers on the rounded stock, I'll break out my trusty fat popsicle sanding stick and carefully apply some pressure making sure the raw edge of my stick (the side that is bare and has no sandpaper on it) is on the nose cone side creating a sharp step down from the OD of the nose cone creating a relatively flat shoulder. Most of the time I have to do a little manual sanding once I remove the completed cone from the lathe and I'm OK with that. Better too large than too small. Every now and then I get lucky and nail it but that's cutting it close with the likes of me. I hope this addresses your question.

Thanks Gary.

I have a 6x33 wood lathe and cutting the shoulder itself is easy but the shank is very rarely so. I think I'm moving the tool consistantly but still get tapers and wows. I've tried a sliding vise to hold and move the tool but setting it up is a major pain. Wish I could afford a metal lathe but thats not possible at this time. I suppose I should job it out if I go back to making commercial models. [for personal stuff its not really an issue :flyingpig:]


Richard

Woot! just had an idea! I know i'm shocked too. All I need is a copy attachment for this lathe and the accuracy will be determined by the accuracy of the pattern used. I need to keep an eye open for sales.

Thanks guys.


Richard

One other tip I'd add that makes things a LOT easier when doing complex shapes, such as the transition and BPC for the Orion capsule and "top hat" that I made for my 1/100 Ares I (build thread in the archives if you want to see the pic)...

Do a "full scale" drawing on light cardboard (like cut from a thick cereal box or a shoe box) of the profile of the cone, exactly the size and shape you want the final part to be. Cut it out of the cardboard very carefully, and save both sides... you can cut the "positive" in half down the long axis of the part for a handy template... this makes it very easy to transfer the exact positions of "steps" that need to be cut into the part, where it will transition from tapered to a cylindrical section, or go from a slight taper to a steeper taper. The "negative" part where you cut it out of the cardboard is an extremely handy template to periodically check the part against, to judge the depth of the taper and if the final shape is shaping up correctly. Just be sure you leave at least 2-3 inches BEHIND the outline of the part on the cardboard so it remains "dimensionally stable".

If you can't cut the pattern out without destroying the negative, you can always trace the positive on another piece of cardboard and then cut it out, by trimming away parts of the "second positive" until you get the exact negative template you need...

VERY handy for complex shapes...

Later! OL JR