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Post by joshuamcduffie on Sept 1, 2020 8:22:36 GMT -5
You should not be seeing the bolt heads protruding through the pad. I've put a lot of hours on mine, and don't see any evidence of this at all. You should be able to buy a new UV-18 base pad. I see that rocktumbler.com is out, but perhaps you could contact Thumler's directly and get one. When you pull off the old pad, check to see if the bolts are seated or torqued down correctly. Also, is it possible you've been putting the wing nuts on too tightly, and pushing the bowl down into the foam, causing the extra wear?
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Post by HankRocks on Sept 1, 2020 8:45:41 GMT -5
I have added two different materials for the under-bowl cushion. First was automotive gasket, has the look of cork but it's not. You can buy it at at most Auto Parts stores in sheets or rolls. Worked well, I finally took it off and added a wore out(in the center) gasket from a Model B rotary. In both case I left the original foam cushion in place. Since I replaced the bolts twice I used a 1/2 inch longer bolt to accommodate for the extra cushion thickness.
During all this I have not noticed any change in performance.
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victor1941
fully equipped rock polisher
Member since November 2011
Posts: 1,983
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Post by victor1941 on Sept 1, 2020 10:58:26 GMT -5
My solution was a little different and very cheap. My neighbor works for a computer company and I showed him the problem and he suggested I try some high density foam used in the computer industry. He had several scraps from work in different thicknesses to test between the bowl and vibrator cradle(base). I cut circular shapes, made an x-cut for the center, slipped on, and tried different thicknesses. 1/2 inch worked for me with good UV-18 motion and the foam shaped very quickly when under load. When I see the need to change this pad I slip off the old one and put the new one on. The top nut screwed on with no problem.
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 768
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Post by lordsorril on Sept 1, 2020 11:54:42 GMT -5
It is possible I don't know my own strength: But, I don't think I over-tighten the wingnuts. I was thinking along the lines of victor1941 and using high density foam cut to size. However, I don't see the need to replace the entire pad. It seems primarily worn at those four bolt spots equally: I would not want to tear everything apart unless I had to: seems like more chance for error if I do. HankRocks idea of using a worn out gasket from a tumbler is an awesome thought! Just for fun: I grabbed my latest Lortone QT12 gasket casualty and put it on the center post--it fit perfectly. Because the gasket has a lip on the top edge that is facing down it seems to provide a bit of a cushion above the bolt heads. All I need to do is to add a few layers of insulation directly on top of the bolts then seal the gasket to the pre-existing foam and try it out. Going to use my repaired bowl for this test (once it is complete). Worst case scenario--I will be back to square one...and out the $10 I spent to repair the bowl.
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Post by HankRocks on Sept 1, 2020 12:14:25 GMT -5
A failed repair is not the worst thing in the world, it's a good learning experience. It also makes you a bit more comfortable when(not if) the next repair situation comes along. Since almost all of my Lapidary equipment was acquired used, repair opportunities arise fairly often. It's good to keep the grey matter from rusting up more than it already has!!!
Good luck.
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 768
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Post by lordsorril on Sept 1, 2020 14:37:52 GMT -5
So I'm nearing completion of repairs on my UV18 bowl. I went with filling the cracks with Loctite Plastic Super Glue and then coating the inside of the bowl and the bottom with JB Clear Weld Epoxy (rated 3900psi). I'm waiting for the resin to cure before I try it out. I noticed that the resin made the bowl feel heavier so I weighed the old repaired bowl to the new unused bowl to see what the weight difference is...I found it interesting: Comparison below (lids not included). Old Bowl repaired with Resin @ 1 year: 800 grams New Bowl - Mint - Unused: 1196 grams Side by side picture of the top edges of the two bowls: ~33% mass loss on the bowl after 1 year of constant use...
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 768
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Post by lordsorril on Sept 6, 2020 15:15:34 GMT -5
Just an update: I coated the inside and outside of the bowl with epoxy resin after patching the hole. The rocks stripped 95% of the Epoxy from the inside of the bowl after 1 week, but, no surprise there--as long as the patch over the cracks held---that was all I was interested in...and it did...The issue is: The inside of the polypropylene bowl itself is now covered in micro perforations on the bottom and the sides (everywhere)--the plastic is too thin overall to continue use. The bowl also deformed on the bottom due to my modified cushion and the lack of remaining rigidity of the material. Thankfully it did not leak from the hundreds of new tiny holes due to the outer coating of epoxy I applied--so at least that was a plus... Final Disposition: Scrap
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