Hello all! This a new one on me!
We are adding a covered front porch to a clients house in January. The client has sketched the front porch columns they would like. They are approximately 8 ft 6 and start as basic tapered columns. On top they would like an 8-10 inch sphere. They have located the spheres (some sort of composite material) but I’m at a loss as how to cut/drill them accurately.
I figure the main support will be simple pt 4×4’s and I can do the tapered part no problem but how do I accurately cut or drill the sphere. Do I cut it in half and then cut out to wrap around the post or drill the middle and slide it on. Either way is there a trick or a jig to accurately marking the sphere??
Thanks in advance for your help!
Eric
Replies
My guess is that these are polyurethene formed balls. Whatever they are, if composite, they are unlikely to be structural, so they would have to be separated in half and fitted around the structural post, or mortised to slip over it before setting the post.
The owners are acting as designer/architects on this, so they need to do the work of one, that means they at minimum need to provide you all the materials data necessary to effect the outcome they desire. If they can't do that, you can't do the work - not without it falling apart or falling down.
Don't take that personal, I couldn't either. And if they spec it oin a way that I know will fail, I actfully point out why or refuse the job.
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Piffin,
Thanks for the warning so to speak. I've been doing work for this lady for 15 years and she's not working as the arhitect. She simply has very ecletic taste. She sketched the look of the columns she wanted but that was it. The tapered column and sphere are simply cosmetic. My question is more regarding how to mark the sphere to cut it half. You don't exactly have a factory edge to measure to and nothing flat to keep a saw from wandering. Any thoughts along those lines?
Eric
A laser might work if you mark the line by hand.
I would use my band saaw, but for just a few, and not having a shop, I would build a box to contain them, like the old handsaw mitre boxes. Think of the magician sawing the fair maiden in half in the sideshow. Th eslot guides the saw, while the box holds the sphere firm.
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Hi Eric,
I'd also be very interested in how to do this. I recently completed a job which included custom railings & balusters on an antique porch. It involved drilling 3/4" holes in several dozen 2" wood spheres. I figured "No problem, use the drill press." Even so - I had a difficult time getting the holes exactly in the center.
All I can suggest is to get extra spheres to screw up on!
LOL
Do you have access to a lathe?
You can mount between centres to find opposite points or even mount a bit in the tailstock and drill right there .......... maybe just thinking out loud..........hmmmm
Rik
To drill into a sphere (heading for the center, and perpendicular to the surface), use a drill press.
Set up the drill press with a sacrificial table, securely clamped or fastened.
Drill a large hole in that table, but smaller than your sphere.
WITHOUT MOVING the table or drill press head, remove the large drill bit and put in the size you want to drill into the sphere.
Put the sphere into the hole you just drilled in the sacrifical table and drill your hole.
The hole in the table centers the sphere, and should work if you don't change the table/quill relationship.
You could also drill a hole in the table, then in your workpiece, as above. Then put a protruding dowel or something in the table that will fit in the workpiece hole. Then drill a second hole in the workpiece, and it will be 180° away from the first hole.
Then you could use these holes to mount the piece on the lathe and halve it with a parting tool. Just taking a sphere and tying to get it perfectly perpendicular between centers would be difficult, I think.
Hope this was helpful.
Pete Duffy, Handyman
My first thought is to make a plywood box that the sphere fits in snugly, and then through the box on the table saw. The sphere would have to fit perfectly in the box though. If it's a 9 inch sphere, you couldn't cut all the way through with a table saw, but you could finish with a hand saw or band saw.
zak
I was thinking the same thing but with a couple refinements. First off, each sphere would need its own jig since the jig would be compromised with the cutting process. I'd make the inside of the box exactly the dimension of the ball for all dimensions (h, w, d) and pin nail the sphere to each jig box to keep it secure (out of the cut & milling line obviously). Index all the boxes so you can maintain alignment if your settings are off just a bit. Set up a table saw and cut all four sides of the box with the blade at maximum height. Finish with an appropriate hand saw or if you have access to a big enough band saw, that would be the best.
Once they're all cut in half, line them up end to end creating a long row of half spheres with the cut side up. Set up a guide for your router and gang cut them all at the same time. If the posts are not structural, you could get away cutting away some of the bulk on the posts themselves to minimize how much milling it would take to accomodate the spheres to your posts. Sounds like a bit of a challenge but jiggable...
I recently had to centre drill 40 spheres, though they were only 2" dia with a 15/16" hole it should work for you. .I used a lathe .First I mounted a block of wood on the face plate and turned a conical depression to allow the sphere to sit in it .Then with a fly cutter cut a hole in the centre of a piece of 1/4 ply a bit less than the diameter of the sphere.This was to retain the sphere in the conical depression.By putting a forstner bit in a jacobs chuck in the tailstock you can drill through the sphere ,on centre with great repeatability,using the faceplate to rotate the work.
Edited 11/29/2005 9:24 am ET by jako17
I'd make the hollow cone as Jako17 describes, then bolt it down to the drill press table, using the butt of a bit in the chuck to get it perfectly centered. The spheres can then be drilled with less setup work than tying them down with the 1/4" ply. The diameter of the circle of contact between the cone and sphere needs to be fairly large compared with the diameter of the sphere, like maybe in the 70 - 90% range. With good friction there, you can just hold them in by hand while you drill.
-- J.S.
part them in half on a lathe?
make a box or rough table with the plywood top exactly half the height of the sphere.* cut a perfect circle the diameter of the sphere and drop that sucker on in.
how you'll keep it perfectly braced is up to you -- perhaps opposable wedges at exactly the north and south poles.
now might also be a good time to pencil a few tick marks across the two sides you'll be cutting to help with re-alignment..
use your biscuit jointer to float around the sphere and cut it in half. If the depth is too much for the jointer, don't worry -- that fancy japanese saw will cut it through -- only the outside edge has to be 'clean'. while it is in the jig, make sure you leave enough 'chicken' still attached to the sphere so the top half doesn't drop. you'll pull it out of the jig with about 350 degrees removed. finish it up with a hand saw. you can re-use the jig over again without damaging it.
*remember to factor in the center point of your biscuit cutter in determining the height of the table.
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Eric Paulson - It's actually Pinkston so don't worry, you haven't lost it yet.
Thanks for all the replies! I don't have access to a lathe but do have a small drill press. I don't think it has enough travel capacity to drill throught the sphere though. I think the "box" idea seems the easiest. Build it tight, pin the ball in place and run it through the table saw. Finish with hand saw. Use router or table saw to plunge out space for the post.
I'll be sure to post a picture of the jig and finished project in mid January - Thanks again for all your creativity.
Hi Eric, you would not happen to be in mass?
Nope - Just south of Chattanooga, TN
Contact the sphere source/manufacturer & tell them you need some halves. Might be a stock item, might be something they have a simple answer for.
Joe H
Before you cut them in half, you might be sure you know how you are going to join them back together. Some plastics are very difficult to join. Are the spheres solid or hollow. A thin shell will give you very little surface area for an adhesive. If the spheres are not going to be painted and will be exposed to sunlight, some plastics do not take UV exposure very well.
I would probably be included to leave the spheres whole and figure out some way to attach them to a molding or frame that would be attached to top of the post. But then, I don't have too clear of an idea as to the specific design parameters...
The balls are solid polyurathane, so joining them back shouldn't be to bad.
I check with the manufacturer - no halfs available - goo thought though.
Thanks!
Eric