Sphere Jig

[Peter Blair]

I wonder if anyone has made a sphere jig that rotates in the vertical rather than the horizontal position?
I have a home made one made that rotates parallel to the lathe bed. It scrapes rather than cuts. I use a 1/8" high speed steel cutter but sure get a lot of tear out that requires sanding.
I know, I know, there will be lots of you who say I shouldn't use a jig at all but with the hollow 2 piece spheres I like to make I really need fine tool control and am not quite able to get a wall thickness close to 1/16 by hand.
It would seem to me that if the bit were riding the bevel I should be able to get a better cut.
There is at least one commercially available model, I have a threader made by the same company and it works fine but really don't want to spend the extra $$ and anyway I truly like to make jigs for my lathe.
Here's a unfinished globe to give some sense of what I am making. Sorry about the photo but I have temporarily lost my photo booth/set-up.
310225

[Marvin Hasenak]

Rig up a ball cutting jig with a trim router and use a router bit to do the cutting. The speed of the lathe along with the speed of the router should get rid of the tear out problem. I learned that from the fishing lure makers.

[Thom Sturgill]

Could you rig up a router handpiece instead of a scraper? Kind of like the FluteMaster?

[Peter Blair]

Great ideas guys. Thanks for the suggestions, I now have all sorts of ideas running through my head. I already use a router with my lathe now I just have to figure out how to pivot it the same as my other jig and exactly what bits I should try. I'm very excited. I would like to figure out how to have the same set-up route the inside of the hollow spheres as well. Now to the drawing board!

[roger oldre]

this does a great job inside:

https://www.youtube.com/watch?v=k13-ikhy6X4&feature=player_detailpage

[roger oldre]

works like this: (at about 2:30)

https://www.youtube.com/watch?v=Z1sf00vxB3M&feature=player_detailpage#t=14 9

[Peter Blair]

Thanks again everyone. I think I'll stick to trying to devise a jig that works with my router.

[Ron Rutter]

Roger. You are heading for some very serious lung problems!!!!!!!!!!!!!!!!

[roger oldre]

Probably. I started out in my dads dads shop. His version of babysitting at 4 years old was to have me pick fishing bobbers out of the sawdust behind the lathe. Over the years we turned almost five million. I have never smoked! good thing right? lol I have been in the asbestos removal field though. I do fiber glass and body work, paint, sheet-rock and concrete. I do wear air filtration much of but not all of the time. lungs are good but I did have a run in with leukemia three yeas ago. thanks for the concern!

[Peter Blair]

Hi Marvin. I spent the day in the shop trying to figure out how to set up my trim router to do as you suggest.
Not gonna work for me, at least the way I have my router mounted. It's just too bulky to get it in close enough on the head stock end.
I am now working on assembling a Foredom hand piece but am doubtful that it is powerful enough to do the jog. Should know by the end of the week.

[Marvin Hasenak]

I think the Foredom has enough power, I use my Foredom to cut flutes etc., with a router bit on the large handle. Search Izzy Swan You Tubes, he has a lot of videos, but some are making spheres with routers.

[Thom Sturgill]

Check out ht e guy that makes the Flute Master (https://www.youtube.com/watch?v=Te362v5H03s). He uses both a Foredom/Weecheer and an air die grinder with his rig. Richard Morris (http://richardmorrisart.com/site/pierce-carved-cherry-ball-on-a-pivot-stand/) gave a demo of a home-brew sphere rig at the Florida Symposium this year. Might be worth talking to.

[Peter Blair]

Thanks again Thom. Actually I have made a similar jig to the one Richard Morris uses. I built it before I discovered him but do use his techniques to hollow my spheres. I looked at all the videos of the Flute Master but an not quite sure if it is the tool for me, for lots of reasons.
Here is a picture of a commercially available one that rotates vertically rather than horizontally like mine. In your experience do you think this motion and tool presentation would cut more cleanly than one like Richard uses?
310430

[roger oldre]

the flutemaster is only fixed in two axis. the third would be to manually maintain perpendicularity to the axis of rotation.. With this also the template has to be manipulated depending on the size and presentation of the tip of the cutting tool. as for the Morris type tool I would suggest using a bushing made of uhmw between the pivot shaft and the socket it goes onto. with bearings it is too fee to move and can lend to inconsistent feeding. it is possible to make a similar tool that will cut on the inside and out side by reversing the arm and using two individual pivot holes for the two operations. rough turn. chuck up for inside cut. rough cut inside. drop tool onto post. finish cut inside. cut tennon if you use one. reverse half of sphere. rough cut outside. finish outside. repeat for the other side with the socket or other half of tennon.

[Don Bunce]

Making something along the lines of a tool post grinder(used on metal lathes) might work well.

Here are plans for something similar that can be used with router bits.

http://www.billooms.com/Resources/OTCutting/DrillFrame2Construction.pdf

[Peter Blair]

Don, this is really nice looking and I'm certain it would work great but I am not certain that I could make the unit as well as you did, and I really don't have a means to power it as you do. Thanks for the ideas.

[Thom Sturgill]

Peter, I only recommended that you look at FluteMaster to see his mounting for the grinder/foredom handle . For a sphere you must rotate around the centerpoint which I'm sure your rig does. Morris had to go through a critical setup each time he uses his rig. That could be improved by having guides on the bottom of the mounting plate that guarantees alignment to the bed.

I'm not sure that there would be any advantage to rotating vertically, horizontally or diagonally. Conventional wisdom is that a scraper should cut on or slightly above the center line with a slight downward slope at the tip. This would tend to lend itself to a horizontal motion IMHO.

On the other hand getting the center point right only requires a one time set up for the banjo mounted vertical solution. It would seem that that would cut from the end to the vertical equator stepping inward as you remove material and then you would have to remount and that would be problematic. You would need a cup to hold the sphere and some way to hold pressure but that might get in the way of the rig. I would have to see one in operation to see how they handle that.

[Peter Blair]

Understood Thom.
Thanks for the suggestions.
In action the cutter is simply set up on the center of the lathe and then lowered after each cut to finish the sphere. It appears in the video to cut rather than scrape . .
Yesterday I messed around in my shop and made a few modifications to my jig. I now am utilizing a small Hunter "cup" style carbide cutter which cuts much cleaner bit with it on center it tends to be a little grabby if too much of the cutter is involved in the cut. This is not a big deal, just means that I need to make sure I cut fairly close at the headstock end before using my jig. It cuts clean enough that I think I will only need to start sanding at 220 rather than the 120 that I have been starting with.
This cutter comes with a 1/4" square shank that is raked and tilted a little but because my jig uses both sides of the cutter I had to set it up with the cutter top parallel to the ways.
I will continue to see if I can devise a router based jig but from what I have on hand the cutter is too close to the mass of the router to get very close on the Headstock end.

Thanks again for all your suggestions.