Swede Posted April 4, 2008 Share Posted April 4, 2008 This is a bit of a continuation of the previous thread where we were discussing standard plumbing test plugs as end caps for PVC pipe sections. I was thinking of using heavy plastic bag material, but figured there'd have to be a better way. I think there is. I start with the Oatey brand plug. This is available at Lowe's, as are all the other materials necessary to modify them. http://www.5bears.com/firew/fwp001.jpg They consist of two plastic disks, a deformable and thick rubber ring, and a 5/16" carriage bolt. The head of the bolt is the metal we are concerned with. Beneath the head is a rubber washer. Remove that. http://www.5bears.com/firew/fwp002.jpg We are going to use epoxy putty to fill in the plastic cap and cover the bolt. Those who have worked with the epoxy putty in a stick know that it is some pretty amazing stuff and should easily withstand the abuse of a ball mill. Epoxy on plastic is more of a mechanical bond than anything, so it is best to at least roughen the plastic. I used a dremel tool to create some undercuts and generally roughen the plastic... http://www.5bears.com/firew/fwp003.jpg Link to comment Share on other sites More sharing options...
Swede Posted April 4, 2008 Author Share Posted April 4, 2008 This is the brand I used. Lay your stuff out and be ready to roll, because it sets in about 10 minutes, no more. http://www.5bears.com/firew/fwp005.jpg Mix the epoxy putty. Roll a bead like play-dough and place it below the head, like so: http://www.5bears.com/firew/fwp006.jpg Then, tighten the screw down pretty hard with the supplied wing nut. http://www.5bears.com/firew/fwp007.jpg Build up the rest of the encap into a mound of smooth epoxy. I recommend using vinyl or butyl gloves. I actually chucked the bolt in my lathe and on a very slow speed, used the palm of my hand and fingers to give it a nice shape. You can use dabs of water; that will help smooth it out. This is what it looked like: http://www.5bears.com/firew/fwp008.jpg It will get quite warm. After it sets, reassemble the plug. Your plug is now ready to do some serious ball milling! I like the concept of plugs, because it means you can make barrels cheap, plentiful, and of any length. I'm confident this stuff will hold up well. If not, I think it should last long enough to make it worthwhile, and if it breaks or wears out, it can always be rebuilt. http://www.5bears.com/firew/fwp009.jpg Link to comment Share on other sites More sharing options...
ST1DinOH Posted April 4, 2008 Share Posted April 4, 2008 thats some nice clean work there... but i wonder if it's possible to find a replacement bolt thats made of plastic? i've seen them before so i know they exist...but where you would purchase one is beyond me... the idea of the bolt is to apply a "squeezing" force to draw the two plastic plates together correct? not sure on the PSI required here but i'm sure some of the denser plastics out there could withstand the force it would require to squish that rubber ring to grip the inside walls of the milling chamber. i only recomend this in case the mechanical action of the grinding media begins to deteriorate that epoxy dome at all. if someone can find plastic threaded bolts to fit it would eliminate the problem all together would it not? behold...the magic of google http://www.google.com/search?hl=en&q=plastic+bolts more specificly a site like this http://www.voltplastics.com/catalog.html hope this works as a secondary option. Link to comment Share on other sites More sharing options...
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