Replies

1. 
   forestgirl | Oct 25, 2009 11:07pm | #1

   I'll be interested to see the responses you get to your query.  Having just finished my first turning class, I'm curious as to what challenges you'll face.  In the class, it appeared that turning a round ball was pretty easy once you had a few miles at the lathe in practice.  Turned between centers, they were true as long as they didn't slip (we had one glue block that came unglued part-way through, the stock slid over 1/8" and then things got a little quirky).  Also, we turned stems (like your dowel, yes?) that were very, very small -- I was surprised to get mine down to ~1/8"

   This was all done with one or two standard tools.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 
   
2. 
   zolton | Oct 26, 2009 12:46am | #2

   If you're only doing the one table - or maybe even if you're doing several - you might be overthinking this. You can purchase round wooden balls from a number of different manufacturers for just a few bucks.

   Drill a hole through the balls, insert an appropriately-sized dowel rod and get on with the rest of the project.

   While you could certainly go through the gyrations you're proposing (and paying big money to have a one-off tool made), there is something to be said for taking the easy way sometimes.

   But you don't even have to purchase the balls pre-made. You could pretty easily do the turning yourself. The dowel/tenon ends give you the means to turn them between centers. Also, you don't need to have a special scraper made to fabricate round wooden balls the way you're describing them. And you'll get a far-better finish from a skew chisel than from a scraper, and way less sanding to boot.

   In the final analysis, the balls won't have to be perfectly uniform or round. Aside from those who measure such things with precision instruments, the eye sees only perfection..

   Zolton

   If you see a possum running around in here, kill it. It's not a pet. - Jackie Moon

1. 
   Rossman | Oct 26, 2009 02:26am | #4

   Zolton and Jako:

   Thanks for the insight. I think I will just sharpen my tools and get to work turning the balls.

    

    

   Edited 10/25/2009 7:30 pm ET by Rossman

1. 
   jako17 | Oct 26, 2009 03:19am | #5

    Rossman  Sorry I forgot one most important thing before you start. make a template out of laminate or thin metal .Drill with a holesaw or fly cutter a hole the diameter that you need ,cut it in half along the diameter .Then reduce the ends by a little more than the spigot radius so you can stop the lathe and test the shape. The first two may seem eternal but like most copy turning once you get your eye in they go quickly.

2. 
   islanddog | Oct 26, 2009 05:34am | #6

   And, if your turning skills are not super sharp, you can pretty easily modify a card scraper to finish up the surface. Simply trace the circumference, cut the scraper using an abrasive wheel on a dremel tool or somesuch, clean up the cut with a file, burnish and turn the edge. Don't overheat the edge.... go slow.

3. 
   jako17 | Oct 26, 2009 02:19am | #3

    Depending on the number of spheres you need it is a simple matter to turn a cylinder of the required diameter layout the spigots and diameter along the axis and turn with a skew or if that is too difficult to handle a gouge with a long grind. Just roll the tool down the end grain .You should end up with a burnished finish far smoother than scraping tools. Just burnish with  a handful of shavings and call it done. 

4. 
   philip | Oct 26, 2009 09:10am | #7

   Ross,
   I do think you are over-complicating this.
   I assume you have a small number to make like four or so, so the easiest way to produce them in the absence of a ball making attachment is to turn them between centres with the end spigots in situ: if the diameter of the ball is X then the distance between the spigots measured at the point of contact with the ball face is also X-that is the first point.
   The second point is the need for a template which again will have a radius of X/2 and a width of X.
   So you just turn a cylinder to diameter X then use a parting tool to define the distance between the spigots-then remove the waste, checking regularly with the template until it fits. Turn them one at a time.
   No need for form scrapers at all-in fact that is a good way to get a dig in.If you are not a confident turner then just use scraping chisels to do the whole thing: that is the way I did it on the one occasion when there was a very similar requirement.

   Philip Marcou
5. 
   Samson | Oct 26, 2009 06:36pm | #8

   How perfect do the spheres need to be?  I'm pretty much a beginning turner, and often practice with scraps turning spheres with either a gouge or skew.  It's not hard to make something that is pretty round straight from the tool.  What would be a bit harder is making them all the same exact size.  If you can tolerate slight divergences, then this sould be easily done by even an intermediate turner. 

   The purpleheart sphere in this bowl is about the size you're talking about.  Neither of these was sanded (which would have perfected them more):

   View Image

   
   

   ---

   Edited 10/26/2009 11:58 am ET by Samson

6. 
   giraffelt | Oct 27, 2009 12:42am | #9

   In his book Woodturning Wizardry, David Sprangett describes a simple jig for turning balls. It basically just holds a cutting bit at the centre line of the work and swivels in an arc. with each pass of the jig you advance the cutting tool - a bit tedious so it helps to rough out as much as possible free hand. its a simple jig to make and has the advantage of allowing you to be precise in dimensioning the ball. the fact that you want to have tenons on each end actually simplifies things in that you don't need to free hand the ends.

   LT

1. 
   Rossman | Oct 27, 2009 01:28am | #10

   As usual there is a lot of good advise out there... thanks to all who have commented.

   I think I will turn the dowels first then use a skew to simply cut from the hemisphere down to the poles. This should be a fairly smooth cut because it is with the grain. I will definately use a profile guide/template/guage of some sort or various sorts. I will experiment with a guage that is the true profile of the finished ball-and-dowels to check as I go with the lathe stopped. I will also try to make a custom scraper from a card scraper cut to the profile and maybe one cut to a lot less than half a circle and move it in an arch. I did not plan on doing this project soon but my interest has been piqued by everyone's comments so I may be giving some feed back soon.

   Thanks again for all the ideas.

   Ross Welsh

7. 
   PSeverin | Oct 27, 2009 01:37am | #11

   Wouldn't it be easier to buy four or eight 2 inch wood spheres from Rockler? I know there's the challenge of making them, but $150 and weeks wait to even begin would make me check my sense of proportion.

   My suggestion is to buy the spheres, drill a hole and place a dowel in them. Even that is not as easy as it seems. Otherwise just approximate the spheres with the tools you have. Nobody's perfect.

   Peter

1. 
   jako17 | Oct 27, 2009 02:00am | #12

   I dissagree with you PS. It is extremely easy to drill holes in spheres .First you set a block of wood on the faceplate then turn s hemispheric depression in it that is a slight bit smaller in diameter than the ball.Next fit a forstner in the tail stock and bore about 1/4 " relief into the cup.Then take a piece of  1/4  " luan ply drill a hole 2/3 the diameter of the ball and fit it to the block on the faceplate with 2 long screws. This acts as a collar to capture the sphere.If you take your balls and restrain them in this way and use the forstner to drill the spheres all your drillings are centered

2. 
   Rossman | Oct 27, 2009 02:04am | #13

   Peter:

   Like others have mentioned, I think that you are right about me over thinking this project. When work is slow I tend to make grandiose plans on paper because I can and because it's fun. After reading other's suggestions my approach will be to just sharpen my tools and turn some 2" balls. I think will use a template to check the final size. I will be using Douglas fir and alder which are probably not stock items for Rockler but I will check.

   Ross

8. 
   Moksha | Oct 27, 2009 04:25am | #14

   Rossman,

   I've always wanted to make a wooden ball turner jig by copying the methods
   used by machinists using metal lathes.

   http://www.bedair.org/Ball/ball.html

   http://littlemachineshop.com/products/product_view.php?ProductID=2568

   http://www.omwcorp.com/prod_lrt.shtml

   I started to make one of these one time to make croquet balls; however,
   it never was completed. The ideas at these web sites do provide
   a pretty good guide on how to make such a jig.

   Moksha