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Sphere Cutting Jig for the lathe #1: Sphere Jig

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Blog entry by Jim Jakosh posted 09-16-2015 09:47 PM 2801 reads 5 times favorited 28 comments Add to Favorites Watch
no previous part Part 1 of Sphere Cutting Jig for the lathe series no next part

I have a job in the future to make some perfect spheres and I could do it with a template and lathe tools but I have often thought I’d like to have a jig to swing the arc to cut spheres. so I decided to make one that will cut convex spheres and concave pockets. I had some sketched but then started looking at what was commercially available and found the Carter Perfect Sphere jig. I followed that design since they had put in all the engineering and all I had to do was determine the size and workings of the parts of the jig.

I used aluminum for the arm and fitted it with a ball bearing that was laying around the shop.

I made the center post adjustable for a 15” or 16” swing lathe. The top of the post is drilled out to hold the horizontal cutter arm with the center shaft that advances with the turn of the handwheel in the back. I could not see how Carter made their adjusting mechanism so I devised one with a ball on the screw and a hole in the cutter arm that works very well.

I made the base mechanism adjustable for different gaps in the bed similar to the Carter design. I scribed the width lines on the bottom instead of the top.

I made some support rings off center so I had a thicker area for the thread without going to a huge diameter.

All the screws that go against the steel shafts have a brass insert in the end to prevent galling.
The horizontal bar has a flat on top and one at 15 degree to either side for doing a shear scrape cut in either direction ( A Carter idea).

The handle on the swing arm is Rosewood.

I made a sample sphere out of a piece of mesquite just to try it out. It cuts very smooth. The cutter is tipped down at 13 degrees. I measured that from a still shot of the Carter tool on You Tube. I think that idea has merit in hollowers as well. The tip is a round Hunter carbide insert that comes with a 4 mm screw.

Here are some shots of the assembly and the parts layout. The steel round parts are coated with Gun Bluing so as to not add to the diameter and yet protect from rust.

Now I’ll need a box for it!!
Also,
I have started on 2 pair of wooden cups (2” and 4”) to hold a partial sphere in order to cut the ends round and make it a perfectly round piece. Finding exact center again will be a challenge, I think.

Cheers, Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!



28 comments so far

View Redoak49's profile

Redoak49

1954 posts in 1454 days


#1 posted 09-16-2015 10:15 PM

Very impressive…..we will be anxious to see some finished spheres.

View Mark Wilson's profile

Mark Wilson

1756 posts in 529 days


#2 posted 09-16-2015 10:26 PM

As though “finding the center” is a challenge. Jeeze, Jim. I don’t think you know what difficult is. You’re a freakin’ genius. You’ve been keeping secrets.
Now. If you’ll look at pictures of Shopsmith Mk5, and pictures of bowl coring devices, I’m sure you could help me figure out a set up I can use. Your brain brain works, evidently, on levels mine hasn’t yet reached. PM me with any ideas, if you don’t mind.

-- Mark

View HillbillyShooter's profile

HillbillyShooter

5811 posts in 1758 days


#3 posted 09-16-2015 10:44 PM

Extremely fine work—beautifully done and far above my pay grade.

-- John C. -- "Firearms are second only to the Constitution in importance; they are the peoples' liberty's teeth." George Washington

View Jim Jakosh's profile

Jim Jakosh

17172 posts in 2571 days


#4 posted 09-16-2015 11:01 PM

Thanks for the nice comments.
Hi Mark, you just gave me another idea. Since this will hollow and cut the outside, If I left the pivot locked in place, I could cut the inside and outside of a bowl with it and get a perfect wall thickness. I would have to do something less than 180 degree so the cutter can come out of the center okay.

cheers, Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View kiefer's profile

kiefer

4881 posts in 2133 days


#5 posted 09-17-2015 12:35 AM

Must be satisfying to be able to build a tool like this in your own shop .
Great looking tool Jim but that rusty bolt has to go .

BTW what size of box would it fit into ?

Klaus

-- Kiefer https://www.youtube.com/user/woodkiefer1/videos

View shipwright's profile

shipwright

7174 posts in 2264 days


#6 posted 09-17-2015 12:39 AM

Pretty slick Jim.
I love the way you think and your ability to follow through in the real world.
This is one sweet piece of work.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

View Arlin Eastman's profile

Arlin Eastman

3557 posts in 2027 days


#7 posted 09-17-2015 01:41 AM

Jim

How do you like that design? Do you think it is better then mine?

Is it easy to rotate back and forth? How big a sphere can you make?

I really like how you can whip up something so fast.

That reminds me of a guy here Roger something who did a DVD on what you made. I will try and find it or him for you.

Arlin

-- Please help me help other Vets click..> http://www.gofundme.com/m1abko.....It is always the right time, to do the right thing.

View BobWemm's profile

BobWemm

1814 posts in 1392 days


#8 posted 09-17-2015 02:05 AM

Geez Jim, you never cease to amaze me.
That jig is something to be very proud of.
Congratulations on your skills.
Bob.

-- Bob, Western Australia, The Sun came up this morning, what a great start to the day. Now it's up to me to make it even better. I've cut this piece of wood 4 times and it's still too damn short.

View Jim Jakosh's profile

Jim Jakosh

17172 posts in 2571 days


#9 posted 09-17-2015 02:13 AM

Thanks Klaus, Paul and Arlin.

Hi Klaus. That bolt it is not that rusty, the photo in that light turned everything brownish. It is the bottom bolt that fastens the post to the arm. I’m running short of socket head cap screws so I use everything I have without buying anything. I did have to buy that 1” block of aluminum. This box needs to be 5 1/4×7 1/2×11 1/4 ….......inside dimensions. I drew it up tonight. I’m thinking 6 pieces….. all lock mitered…. and then cut on a curve to open.
Hi Paul. It does work slick too!!
Hi Arlin. I know you have plans to make the cuts over the top with a skew type cutter but I have to say this cuts smooth. I wrote Carter and they said they put that ring insert on an angle for a better cut and they were right. I measured it at 13 degrees from the video with a straight on photo and it worked. It rolls on a bearing and it easy to rotate. I can off set the cutter to either side to get more clearance just like the Carter. I don’t have a video, but take a look at theirs. I’ll see if I can put it in here. It was not fast. I spent a whole week solid on it and three pages of drawings…modifications all the way.

Cheers, Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View doubleDD's profile

doubleDD

5241 posts in 1509 days


#10 posted 09-17-2015 02:14 AM

Excellent thinking Jim. Great way to keep the mind busy. Wish I had the tools to do some metal work like that.
You say you figured out the possibility of hollowing the inside. I have been making stick bobbers for my son and thought of making a round one for myself as a novelty item. Looks like you may have that figured out.

-- Dave, Downers Grove, Il. -------- When you run out of ideas, start building your dreams.

View Jim Jakosh's profile

Jim Jakosh

17172 posts in 2571 days


#11 posted 09-17-2015 02:23 AM

Thanks, Dave. I love it when I can get back on the metal lathe again. I got to use a lot of my own tools that I made to make this tool….like the boring head in the mill and the fixture for drilling exactly on center of round pieces up to 2” diameter. It drills within a half thousandth. I spent 40 hours grinding that fixture to get it perfect.

Cheers, Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View Joe Lyddon's profile (online now)

Joe Lyddon

9447 posts in 3518 days


#12 posted 09-17-2015 04:38 AM

Looks COOL, Jim…

A short video would be nice to see how it really works though…

Thank you!

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: http://www.WoodworkStuff.net ... My Small Gallery: http://www.ncwoodworker.net/pp/showgallery.php?ppuser=1389&cat=500"

View UncleStumpy's profile

UncleStumpy

707 posts in 1778 days


#13 posted 09-17-2015 05:49 AM

Really cool!

I think I will stick to just eyeballing it though. Or maybe actually buying a couple of balls if i need them perfect.

Amazing jig!

-- "They don't want it perfect - they want it SPECIAL"

View Bob Collins's profile

Bob Collins

2321 posts in 3149 days


#14 posted 09-17-2015 10:13 AM

Very smart work there Jim, must be great to see something and then turn around and make it. Well done.
Using that tool will take all the fun and challenge from turning a sphere by eye and feel but sure will make the task easier.

-- Bob C, Australia. I love sharing as long as it is not my tools

View Jim Jakosh's profile

Jim Jakosh

17172 posts in 2571 days


#15 posted 09-17-2015 10:56 AM

Thanks Joe, Ray and Bob.
Hi Joe, here is the Carter video. Mine were like that: https://www.youtube.com/watch?v=EHLhhV6unYk

Hi Bob. I have wanted to make one of these for a long time but never had the need. I can see many uses for it now.

Cheers, Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

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