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Post by Drummond Island Rocks on Mar 25, 2020 13:58:40 GMT -5
This is the rough mock up. Will completely disassemble and build a final version after the statewide lock down. This is functional so I can at least use it while cooped up at the house for the next few weeks. The two rocks I used for a test run will now only need 1 to 2 weeks in stage one instead of possibly needing 6 to 12 weeks. This is not a quite grinder. Not sure this sheet metal arbor setup was designed to have 15 pounds of steel spinning on it. I think a poly arbor would be a better choice. Not real happy that there is not a weld where the center section meets the base pan. Water goes into the cavity of the center section. I think this is a fragmented membrane Lake Superior Agate. toiv0? Dendritic opal Chuck
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NDK
Cave Dweller
Member since January 2009
Posts: 9,439
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Post by NDK on Mar 25, 2020 14:22:04 GMT -5
Hey Chuck, I was just razzing ya. Gotta keep it light, right bud? ✌️
Looks like it does quick work of removing that rind.
I bet after the powder coating is done a bead of silicone wouldn't be a bad idea around that center section.
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Post by Jugglerguy on Mar 25, 2020 15:57:58 GMT -5
Whoa, that opal cleans up nice!
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Post by toiv0 on Mar 25, 2020 16:48:43 GMT -5
Yep right on with the laker I'd. Going to be a time saver.
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Post by Drummond Island Rocks on Mar 25, 2020 18:11:54 GMT -5
Hey Chuck, I was just razzing ya. Gotta keep it light, right bud? ✌️ Looks like it does quick work of removing that rind. I bet after the powder coating is done a bead of silicone wouldn't be a bad idea around that center section. Thanks. Caulking that seam came to mind. I was just surprised there was not a weld there to begin with. Chuck
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Post by RocksInNJ on Mar 26, 2020 0:25:25 GMT -5
Super sweet!
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Post by Drummond Island Rocks on Mar 26, 2020 9:37:15 GMT -5
Whoa, that opal cleans up nice! Thanks Rob. I have had about 12-15 pounds of that opal sitting in a box for the last 4 years. I had seen a listing on craigslist for a gemlap trim saw at a local pawn shop. When I got there and bought the saw they tossed in a bunch of rocks that they got with it. They had no idea what anything was and I walked away a happy camper. I have been hanging onto that material thinking it should be cabbed but I might sneak a few into the tumbler. I have cabbed a couple Chuck
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 29, 2020 6:50:26 GMT -5
Professional build Chuck. Pre-shaping is the way to fine tumbles.
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Post by Drummond Island Rocks on Mar 29, 2020 9:55:01 GMT -5
Professional build Chuck. Pre-shaping is the way to fine tumbles. Thanks JamesP. I do not really plan to preshape any rocks. I was just using that for a test to see how long it would take to remove that much material. I still plan to tumble everything first and just use the grinder for the few spots on each rock that would hold up the process. I have used a good amount this weekend and I still think the arbor is not suited for the wheels. The bearings are just brass slip fit and the housing is stamped sheet metal. 25 pounds of wheels spinning does not sound good on it. I will keep my eyes out for a more robust 8" arbor. Chuck
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 29, 2020 10:18:10 GMT -5
I see. Removing specific defects, concave areas, divots, etc. Such spots can really slow things down, why hold up a whole batch because of 3 rocks that can be touched on a grinder for 20 seconds.
Spinning heavy grinding wheels at elevated speeds can get tricky in a hurry if they grind unevenly to an imbalance situation creating bouncing and imbalance. Always something to keep in mind. Hard to beat robust bearings and well balanced arbors. I think 6 and 8 wheel cab machines benefit from having multiple wheels that may suffer from slight imbalances in each wheel by cancelling some of the imbalances.
In a single wheel system it is probably best to have a cheap high rpm rated diamond wheel so that it can be trashed in the event of it becoming unbalanced. Tricky to fix if +1000 rpm. And mounting the wheel directly to a precision balanced shaft like that of a normally dynamically balanced motor output shaft. A cheap source of fine balance.
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Post by Drummond Island Rocks on Mar 29, 2020 14:11:32 GMT -5
I see. Removing specific defects, concave areas, divots, etc. Such spots can really slow things down, why hold up a whole batch because of 3 rocks that can be touched on a grinder for 20 seconds. Spinning heavy grinding wheels at elevated speeds can get tricky in a hurry if they grind unevenly to an imbalance situation creating bouncing and imbalance. Always something to keep in mind. Hard to beat robust bearings and well balanced arbors. I think 6 and 8 wheel cab machines benefit from having multiple wheels that may suffer from slight imbalances in each wheel by cancelling some of the imbalances. In a single wheel system it is probably best to have a cheap high rpm rated diamond wheel so that it can be trashed in the event of it becoming unbalanced. Tricky to fix if +1000 rpm. And mounting the wheel directly to a precision balanced shaft like that of a normally dynamically balanced motor output shaft. A cheap source of fine balance. The wheels were balanced at the factory by drilling holes but no telling how accurate at this point. Chuck
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 29, 2020 20:01:00 GMT -5
Bench grinders are notorious for having off balance loads so they build them with heavy shafts and out board bearings close to the grinding wheel to reduce vibration. The bearings are close to the wheels on the machine you posted. Looks like bushings, could have play in them allowing vibration perhaps ? Those may be able to be replaced with face mount ball bearings with a stepped up shaft diameter. The wheels seem to have red spacers for smaller shafts. I believe you used them. This is a hint that these fairly heavy wheels and may prefer to run on heavy 7/8" to 1" shafts to off set any potential imbalance. Shafts keyed ? Wheels keyed ? Other stuff to consider if changing shaft/bearings/pulley(sheave bore). Those are fine wheels probably gotten cheap, should be well worth the modifications to the machine... An example is a real heavy duty bench grinder with heavy structural bearing cups to prevent vibration from commonly off-balance stone wheels.
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Post by mohs on Mar 29, 2020 20:31:02 GMT -5
Way back in the archives I was mentioning how I only use the 6'' flat lap in the early morn so as not to make too much noise for the neighbors Whisper quiet Then after 10 o’clock I start up mofo Mohs
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 30, 2020 4:23:18 GMT -5
Way back in the archives I was mentioning how I only use the 6'' flat lap in the early morn so as not to make too much noise for the neighbors Whisper quiet Then after 10 o’clock I start up mofo Mohs Old heavy iron spinning true for true hearts from the mohs. Or is this the grinder you use for hearts Ed ? If so do you wet wheel ? Spray bottle ? SiC wheel ? Curious mind...
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Post by Drummond Island Rocks on Mar 30, 2020 12:15:19 GMT -5
Bench grinders are notorious for having off balance loads so they build them with heavy shafts and out board bearings close to the grinding wheel to reduce vibration. The bearings are close to the wheels on the machine you posted. Looks like bushings, could have play in them allowing vibration perhaps ? Those may be able to be replaced with face mount ball bearings with a stepped up shaft diameter. The wheels seem to have red spacers for smaller shafts. I believe you used them. This is a hint that these fairly heavy wheels and may prefer to run on heavy 7/8" to 1" shafts to off set any potential imbalance. Shafts keyed ? Wheels keyed ? Other stuff to consider if changing shaft/bearings/pulley(sheave bore). Those are fine wheels probably gotten cheap, should be well worth the modifications to the machine... An example is a real heavy duty bench grinder with heavy structural bearing cups to prevent vibration from commonly off-balance stone wheels. Purely coincidence that a really heavy duty lapidary arbor pops up in my Facebook feed today. About an hour north of me but out of my price range at $550 for a two wheel used arbor. Absolutely perfect for what I need though. Chuck
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 30, 2020 15:40:46 GMT -5
Sweeeeet All problems solved in one purchase. That is a rock solid beast with water management to boot. By the time good pipes, fittings, valves and lighting is purchased and installed cost goes up up. Add motor, pulleys, belts, tray and the budget's cooked. Even has wheels. Well done. Does it have a brand name ?
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Post by Drummond Island Rocks on Mar 30, 2020 15:54:21 GMT -5
Sweeeeet All problems solved in one purchase. That is a rock solid beast with water management to boot. By the time good pipes, fittings, valves and lighting is purchased and installed cost goes up up. Add motor, pulleys, belts, tray and the budget's cooked. Even has wheels. Well done. Does it have a brand name ? By the time I thought about and went back to check it out it was listed as sale pending. Only took two hours. Chuck
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 31, 2020 7:15:04 GMT -5
Dang it man !
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Post by mohs on Mar 31, 2020 19:55:55 GMT -5
All I really know james Is when that mofo is powered on The sparks -friction & electrical- really Fly spark testing that a study
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Post by mohs on Mar 31, 2020 19:58:53 GMT -5
That poly arbor w/ green wheels is happening Chuck ! I need one for Rock'n Heart Factory grind efficient smooth
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