tumblingjake
off to a rocking start
Member since January 2021
Posts: 9
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Post by tumblingjake on Jan 18, 2021 10:14:33 GMT -5
Ok, so I've decided to give some cab cutting a try. Previously I've only tumbled stones, so I'm totally new to this side of things. Instead of spending thousands on a new cab machine, I've purchased an old Covington grinder that needed some love. It has 3 wheels inside the machine, with a 4th polishing pad on the right end. Two of the wheels are silicone carbide 100 & 220 wheels. The third wheel is what I've figured out is a split drum, where you cut and make your own belt. The dilemma I'm having is this: I understand how the split drum works, and getting belts for it would be easy, but doesn't it create a bump in the wheel where the belt folds into the lock? Also the rubber pad under the belt is all cracked, and chunks are missing. I believe I'd have to replace the wheel due to that. I don't really want the bump in the wheel however. Due to the fact that it's on the inside, I cant really go with an expando drum, since there'd be no way to change the belt without taking the machine apart every time. I guess my question to the experienced out there is this: Do I find another split drum, and learn to work around the bump, or is there one grit wheel that you'd just replace it with, and call it a day? I was thinking maybe a 600 grit wheel, but I'm not sure. Any help would be much appreciated. Thanks
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Fossilman
Cave Dweller 
Member since January 2009
Posts: 20,723 
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Post by Fossilman on Jan 18, 2021 11:43:34 GMT -5
I threw my bump wheels away and went to expando drums.. Best move I ever made...
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tumblingjake
off to a rocking start
Member since January 2021
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Post by tumblingjake on Jan 18, 2021 12:07:18 GMT -5
That's what my initial solution was, but I don't think it's the right move for this machine. The wheel I'd be changing is actually inside the machine. I'd have to unbolt the whole shaft at both ends to be able to change the belt. It's an old unit. I'm thinking of just replacing the split drum with a 6oo grit. That would just leave me with 3 grits and a polisher.
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Tommy
Administrator 
Member since January 2013
Posts: 12,989
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Post by Tommy on Jan 18, 2021 12:09:11 GMT -5
Ok, so I've decided to give some cab cutting a try. Previously I've only tumbled stones, so I'm totally new to this side of things. Instead of spending thousands on a new cab machine, I've purchased an old Covington grinder that needed some love. It has 3 wheels inside the machine, with a 4th polishing pad on the right end. Two of the wheels are silicone carbide 100 & 220 wheels. The third wheel is what I've figured out is a split drum, where you cut and make your own belt. The dilemma I'm having is this: I understand how the split drum works, and getting belts for it would be easy, but doesn't it create a bump in the wheel where the belt folds into the lock? Also the rubber pad under the belt is all cracked, and chunks are missing. I believe I'd have to replace the wheel due to that. I don't really want the bump in the wheel however. Due to the fact that it's on the inside, I cant really go with an expando drum, since there'd be no way to change the belt without taking the machine apart every time. I guess my question to the experienced out there is this: Do I find another split drum, and learn to work around the bump, or is there one grit wheel that you'd just replace it with, and call it a day? I was thinking maybe a 600 grit wheel, but I'm not sure. Any help would be much appreciated. Thanks welcome to the forum! With three land-locked wheels I would probably opt for a fixed wheel (600 grit) as opposed to continuing to have to mess with the split wheel. Also an excellent goal would be to replace the two SiC asap with diamond grinding wheels. I was searching the web for photos of a "three inside" Covington - does your machine look like this one below? If it does I'd be tempted to add more collars and wheels - seems like an awful lot of real estate going to waste on that shaft. I might even consider looking for a way to extend the water pans out to the right and adding an expando wheel where the flat disk is currently. As fossilman said an expando in your setup would add a world of possibilities to your cabbing experience. You're going to be seriously limited with two grinders and a fixed wheel. Edited to add: These upgrades would probably require you to look at upgrading stuff - motor, shaft, bearings, etc.  |
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tumblingjake
off to a rocking start
Member since January 2021
Posts: 9
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Post by tumblingjake on Jan 18, 2021 12:14:10 GMT -5
Yes, my unit looks exactly like that one. I was trying to upload the crappy picture I took of it, but couldn't figure out how. I never considered if I could add more wheels to it. I'd have to think a while on how to go about that. Where I would get spacers and collars for this old of a machine may be hard. Maybe I'd have to make them. I have to add a motor anyway. It was missing when I got it. The bearings are nice and smooth so far.
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Tommy
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Member since January 2013
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Post by Tommy on Jan 18, 2021 12:16:35 GMT -5
Yes, my unit looks exactly like that one. I was trying to upload the crappy picture I took of it, but couldn't figure out how. I never considered if I could add more wheels to it. I'd have to think a while on how to go about that. Where I would get spacers and collars for this old of a machine may be hard. Maybe I'd have to make them. Yeah posting photos is a pain around here that's why I went straight to google instead of asking you to upload lol. We are available to help you if you decide to go down the rabbit hole and set up a Cloudinary account. First think to figure out is what is the diameter of the shaft. After that, you should be able to find collars pretty easy on Ebay etc. |
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Post by woodman on Jan 18, 2021 12:17:07 GMT -5
That's what my initial solution was, but I don't think it's the right move for this machine. The wheel I'd be changing is actually inside the machine. I'd have to unbolt the whole shaft at both ends to be able to change the belt. It's an old unit. I'm thinking of just replacing the split drum with a 6oo grit. That would just leave me with 3 grits and a polisher. I would go to a 600 or finer diamond wheel myself. Diamond on all three would be good! |
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tumblingjake
off to a rocking start
Member since January 2021
Posts: 9
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Post by tumblingjake on Jan 18, 2021 12:42:34 GMT -5
Yes, my unit looks exactly like that one. I was trying to upload the crappy picture I took of it, but couldn't figure out how. I never considered if I could add more wheels to it. I'd have to think a while on how to go about that. Where I would get spacers and collars for this old of a machine may be hard. Maybe I'd have to make them. Yeah posting photos is a pain around here that's why I went straight to google instead of asking you to upload lol. We are available to help you if you decide to go down the rabbit hole and set up a Cloudinary account. First think to figure out is what is the diameter of the shaft. After that, you should be able to find collars pretty easy on Ebay etc. Well I have measured the threads on the end where the polishing head goes, and they're 1" 12. So I would guess a 1 inch shaft, but I'll have to get it dismantled to make sure. |
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Tommy
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Post by Tommy on Jan 18, 2021 13:10:25 GMT -5
Well I have measured the threads on the end where the polishing head goes, and they're 1" 12. So I would guess a 1 inch shaft, but I'll have to get it dismantled to make sure. Yeah pretty high likelyhood that it's a 1" shaft but I didn't want to assume. If this were my project I would pull the shaft snd strip everything off it and with the new motor installed spin the shaft and thoroughly clean it to bare metal with super fine grit - emory - then lay out a series of wheels that make sense. Two diamond grinders and two or three soft diamond - wheels and you've got a great machine there. BTW I looked it up and 1" collars can be easily found in bulk packs on ebay and then all you need is some flanges - 1" id washers work. |
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tumblingjake
off to a rocking start
Member since January 2021
Posts: 9
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Post by tumblingjake on Jan 18, 2021 13:22:52 GMT -5
Well I have measured the threads on the end where the polishing head goes, and they're 1" 12. So I would guess a 1 inch shaft, but I'll have to get it dismantled to make sure. Yeah pretty high likelyhood that it's a 1" shaft but I didn't want to assume. If this were my project I would pull the shaft snd strip everything off it and with the new motor installed spin the shaft and thoroughly clean it to bare metal with super fine grit - emory - then lay out a series of wheels that make sense. Two diamond grinders and two or three soft diamond - wheels and you've got a great machine there. BTW I looked it up and 1" collars can be easily found in bulk packs on ebay and then all you need is some flanges - 1" id washers work. Thank you so much for the help. I'll get it tore down, and see what I come up with. I'll let you know the outcome. |
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tumblingjake
off to a rocking start
Member since January 2021
Posts: 9
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Post by tumblingjake on Jan 18, 2021 14:17:35 GMT -5
Also, what would you guys suggest for a polishing pad on the end. I see there's leather and vinyl options. I assume you'd want a nice pad behind it?
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Tommy
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Post by Tommy on Jan 18, 2021 15:31:15 GMT -5
Also, what would you guys suggest for a polishing pad on the end. I see there's leather and vinyl options. I assume you'd want a nice pad behind it? I'm gonna defer to rockjunquie - I know she uses one of those for finishing - or was using it. I use a separate slow speed flat lap for polishing if the stone still needs it after a 14.4k or 50k grit soft wheel. |
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Post by stardiamond on Jan 18, 2021 17:12:05 GMT -5
Diamond wheels have got very reasonable. I like recycling water instead of drip and would put geysers under the wheels using an aquarium pump assuming they will fit. Plug the drain to get the water and drain and wipe down and plug again. Use a canvas pad and diamond paste. 4 inch wheels and you would have a pixie.
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Post by rockjunquie on Jan 19, 2021 10:43:00 GMT -5
Also, what would you guys suggest for a polishing pad on the end. I see there's leather and vinyl options. I assume you'd want a nice pad behind it? I'm not familiar with what goes on the end of this machine. I have a genie and use a lot of different spin on (screw on) Nova pads and a couple with diamond paste. Sorry. However, I have heard it suggested that tin oxide on felt is a good polish. |
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Tommy
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Post by Tommy on Jan 19, 2021 11:56:45 GMT -5
Also, what would you guys suggest for a polishing pad on the end. I see there's leather and vinyl options. I assume you'd want a nice pad behind it? I'm not familiar with what goes on the end of this machine. I have a genie and use a lot of different spin on (screw on) Nova pads and a couple with diamond paste. Sorry. However, I have heard it suggested that tin oxide on felt is a good polish. Sorry - I didn't mean to put you on the spot  I think the Nova pads are the same basic concept ie: screwing the pad holder on to the end of the shaft. The question is is does the Covington shaft have male threads or female like the Nova would screw into. |
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NevadaBill
fully equipped rock polisher
Member since January 2019
Posts: 1,332
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Post by NevadaBill on Jan 19, 2021 13:35:24 GMT -5
tumblingjake, you have a lot of interesting questions here, and I am sure that some might be experienced here with your old model of Covington. I personally am not. And kind of have a difficult time imagining what it might look like. Thanks to Tommy for guessing the model of Covington which you might be trying to describe. And best of luck!
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tumblingjake
off to a rocking start
Member since January 2021
Posts: 9
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Post by tumblingjake on Jan 25, 2021 9:26:58 GMT -5
Also, what would you guys suggest for a polishing pad on the end. I see there's leather and vinyl options. I assume you'd want a nice pad behind it? I'm not familiar with what goes on the end of this machine. I have a genie and use a lot of different spin on (screw on) Nova pads and a couple with diamond paste. Sorry. However, I have heard it suggested that tin oxide on felt is a good polish. I actually have figured out what threads are on the end of my machine, and what all I need to get to physically add the polishing pad to the machine. I just didn't know if there was a basic preference on a canvas versus a leather polishing pad. I also wondered if getting a polishing base with a rubber backing for the pad is the way to go. |
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Post by hummingbirdstones2 on Jan 25, 2021 9:58:25 GMT -5
I think canvas used to be used a lot more than it is today. Leather has been good to us. Felt for soft stones or stones that want a lot of heat.
Rubber backers really make the job easier.
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tumblingjake
off to a rocking start
Member since January 2021
Posts: 9
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Post by tumblingjake on Jan 25, 2021 10:54:01 GMT -5
I think canvas used to be used a lot more than it is today. Leather has been good to us. Felt for soft stones or stones that want a lot of heat.
Rubber backers really make the job easier.
Perfect. Those are the options that I was leaning towards. Thank you! |
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I think the Nova pads are the same basic concept ie: screwing the pad holder on to the end of the shaft. The question is is does the Covington shaft have male threads or female like the Nova would screw into.
