Easy 3 Inch round shell hemispheres

[gordohigh]

I was in walmart yesterday in the kitchen area and saw a couple of hand juice extractors, the kind on a hinge that you squeeze a half at at time. Anyway, they had 2 sizes, one for a lime, which looked about 2in size, and a bigger lemon size that looked like maybe a 3 inch. I didn't have a tape measure but it might be worth checking on. Just a quick evaluation of it seemed like if the size was right that it would be the perfect tool for making hemi halves. If by chance it was a little too big you could probably make an insert for both sides that would reduce the size.

 

Of coarse I realize its a long shot but, ya never know.

[Weasel]

I made a mold for making hemis out of modeling clay, it's easy and it works great. Just make sure you don't use a clay that shrinks when it dries, and make it thick enough that it doesn't crack when you press a hemi in it. I had both of these problems and I have had to make 3 different molds because of it.

 

I just use a ball for the male half of the mold, the only trouble is finding a ball the right size. I have found that most bouncy balls are about the right size for 2" shells. Using a ball also makes it easy to make the mold, you just push the ball halfway into the clay and let it dry.

 

Using modeling clay might not be a good idea to use for larger shells, you would need a lot of clay and it wouldn't be affordable. A mold for a 2" hemi already takes about 3/4 of a small brick size bag of clay. And even though normal, kiln drying clay is really cheap in large quantities, it shrinks when it dries so that's not a possibility.

 

I have also found that making a disk with only 4 triangle cutouts in it works better than making a disk with several cutouts in it. you get more coverage around the shell. That's what they use in this video :

Edited January 31, 2010 by Weasel

[gordohigh]

I have this file, but have never used it. It's at least an idea. Is is probably easiest to put it in a program like photoshop or microsoft publisher so you can print off a template fit to size. Go a little big, and trim the edges to make them fit nicely.

 

A few convenient paper thicknesses

 

4 sheets

 

4 ply poster board - ~1/16"

5 ply poster board - ~3/32"

8 ply poster board - ~1/8"

14pt file folders - ~1/16"

#70 chipboard - ~1/8"

 

5 sheets

 

4 ply poster board - ~3/32"

6 ply poster board - ~1/8"

12pt file folder - ~1/16"

#90 chipboard - ~1/8"

#120/#125 chipboard - ~3/32"

 

6 sheets

 

5 ply poster board - ~1/8"

10pt file folders - ~1/16"

14pt file folders - ~3/32"

#90 chipboard - ~1/8"

#120/#125 chipboard - ~3/32"

 

 

Here is a template I made in open office draw and it wont take much ink, (dotted lines). Also, you can open it in Open office, (a free program just like Office), and adjust the size to fit your need. If you print one, you can tape the corners and cut a bunch at a time.

 

 

Edit, the system wont let me upload it, maybe because its an .odg file so if anyone is interested I can send it to a mod to post.

[Twotails]

I have the same lemon juicer from walmart as mentioned. i will try it tonight! seems promising!

[scarbelly]

For a 2" hemi former, would a golf ball work? I looked online and a golf ball is supposed to have a diameter of "no less than 1.68 inches". Would that be too large, meaning that the finished shell wouldn't fit in the mortar?

[gordohigh]

HDPE Pipe comes in 1.91 and 2.07inches ID so you would need to measure your mortar to see what size you need. A golf ball is slightly larger than my 2in hemis, both plastic and paper. If you use the 2.07 it might work because a golf ball is 1.67in which might give you enough room.

 

 

BTW, I sent the template I mentioned above to Mumbles to post.

[Twotails]

Tried the lemon juicer, and it seems it wont work

Looks like i'll have to make my press after all...

[angelluis]

I made a set of hemis today using approximately this method. We'll see how it looks tomorrow when it's all dry. Thanks for the tut. My first set of homemade hemis failed awfully, so hopefully this will work better. I used a styrofoam ball rather than a tennis ball.

Hello, I made a 1.75" hemi, but I used a golf ball, regular elmers school glue, but I can see how using the carpenters wood glue would work really well and give the shell a stronger, more durable finish. The savings are worth every penny, being a amature at this that helps alot, thanks to the both of you guys so after every thing has been done I will end up with a nice 2" shell

Edited July 26, 2010 by angelluis

[Lionel]

I'm unwilling/unable to work on any sort of compositions currently due to my job, so I've been practicing other things that I consider to be necessary skills, or just something I'd like to try out. I saw this post last night, and since I have a big roll of gummed tape, I decided to try to make a hemi out of some. I Took a plastic ball (the kind you used to see in a ball pit at mcdonalds, etc). First a layer of masking tape to act as a mold release, then five layers of kraft paper tape. A final light coating of elmers wood glue on the outside. I cut the whole pasted ball in half with a dremel since I couldnt find my razor knife... lol. Here's a couple shots of the end result.