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Post by mohs on Jun 16, 2012 16:47:54 GMT -5
Howdy Guys Let see if we can’t start a good Double Dome - Groove & Wrap (DD-G&W) advice thread  What I have here is an ornery stone with a flat spot in the middle of the stone . Scratches ! My normal procedure would be to dome it higher to get into the center & get the scratches out. But in order to do this I’d have to get into the grooved edge. That may have to happen So one of my questions would be Is there a optimum size thickness for DD-GW ? Seems like the minimum should be at least ¼” thick? What about removing scratches that are in a flat spot ? Can you get them out with a shallow dome? Or do have to increase the dome to a least curve the flat spot? I’m not sure I explaining this well and my picture could be better but I’m due to go to Don Jose restaurant (so my blood sugar is off at the moment) :drool: But hopefully by the time I eat someone will have made some sense out this and be able to advise Thanks! Edmostly |
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Post by mohs on Jun 16, 2012 16:49:51 GMT -5
O and feel free to add any advice thoughts experiences you had with this procedure ect..all doesn't necessarily have to do with my problem Luc\jhbreak!  |
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Post by Deleted on Jun 16, 2012 21:01:59 GMT -5
It is difficult to tell without a side view but it looks to me like you could lower the dome to almost flat and get the scratches out. You would have to use PI (which is wrong) or 2r to figure out the arc. I am not a mathematician and I am old school (maybe really old school) so I would use PI because I still think it is right.
Depending on the size of the stone I think that 1/4 inch would be the minimum thickness that you could use to make a DD. If you get your GW edge too thin the edge will chip while you are doing the G which looks pretty bad from the front or the side. Since I bought G burrs too thick I could not use a slab thickness of less than 5/16 to make a DD GW. I do not understand why anyone would want to make a DD GW unless you are putting a swivel on the top. A D GW would look just as good and you have 1/8 for the D and 1/8 for the G. Simple, clean and neat and you do not need PI or 2r to accomplish it so that would leave all the Pie for me.
Jim
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Post by mohs on Jun 16, 2012 23:01:35 GMT -5
That is beautiful Jim ! I see things much more clearly I think you’re exactly right that DD is redundant Just a front D w/a flat back (FB) then a G & W with a swivel bale would be the ticket But I don’t have a flat lap so polishing FB is beyond my capabilities Another point is the chipping of the edge Trying to DD a stone that not thick enough. This particular stone I’m doing well I got the scratches out (mostly) but the grooved edge is real thin. Might end up being to weak? As you can see I’ve domed the one side and that grooved edge is chippy thin!  I’m figuring that a stone thickness should at least be 7/16th thick to do the job justice. Of course, this dependent on how large the cab is going to be But I wonder what the ratio is of: cab size to thickness for doming? There must be a general formula involving Pi ? Thanks ! Ed |
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Post by mohs on Jun 17, 2012 12:40:57 GMT -5
Since I bought G burrs too thick I could not use a slab thickness of less than 5/16 to make a DD GW. Jim Hey Jim would you have a picture of these G burrs ? |
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Post by Deleted on Jun 17, 2012 13:39:09 GMT -5
Here is a post from a while back showing the burr and how I use it. forum.rocktumblinghobby.com/index.cgi?board=ccabs&action=display&thread=52431If your groove is the same on the other side as it is on top you should be ok with it. I figure that if I have 1/32 to 1/16 inch flat below the dome it is ok. I have had some where the dome and the groove met in a point and it chipped off pretty bad. If you are not doming the back side you could have lowered the groove a little so it was centered on the side. I always use a scrap piece of slab to check the height of my groove. I hope this helps because I do not have a formula for PI other than "buy a frozen crust" it is much easier than using 2r. My super duper formula is to buy a complete frozen PI and eat at will. Jim |
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Post by mohs on Jun 17, 2012 14:14:57 GMT -5
Thanks Jim for the link Hopefully other will contribute I'd like to see some input regardless If it turns in a Pi thread that's fine You can bet I'll be eating my Pi between the fence posts ||||||||||||||||||||||||||||| but my Father day project is to finish this DD-G&W hopefully I can post some pics  This was my technique I can tell that I didn't get the groove (G) deep enough so I'll be dremeling later.. |
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Post by Deleted on Jun 17, 2012 15:52:05 GMT -5
You can flat grind and re polish the edge to get a little more depth on the sharp edge but then you will have to make the G deeper which is pretty hard to do if you already have the DD because it will wobble all over the place. I only G if I have a flat back to spin the cab on because I can not see what is happening with the water swirling around.
Jim
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Post by mohs on Jun 17, 2012 16:11:13 GMT -5
well I just ground the back dome ()=BD I see some scratches but going to let it ride So besides the G not being deep enough the overall cab a bit misshape'n which will need some finesse'n better call in a pro! :help: stay tuned though I'll post a pix of my G deepening process on a already ground DD .... hopefully |
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Post by mohs on Jun 17, 2012 17:06:26 GMT -5
manual deepening groove zipping procedure (MDGZ) for an already ground DD  It was how I originally zipped the grooves in my rock’n hearts When both flat sides are zipped & epoxy together waaa la a pre-drill hole really an act of genius !  Sometimes I add 2 S/C disc together, on the Dremel , to widen the groove Then use a single disc to deepen the G I suppose a person with a really steady hand could G a rock with just this method for a W This is the the DD with deepens G using my MDGZ method I’m not multi -task-able enough to hold the camera in 1 hand and MDGZ at the same time  You’ll have to use your imagination mostly |
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Post by Deleted on Jun 17, 2012 17:47:46 GMT -5
Slapping my forehead with my hand. I was not genius enough to think of 2 S/C disc together to make a wider G.
Your G is looking quite nice and straight for using the MDGZ method. How do you use water when you are using the MDGZ method? Are you clamping the C and holding the D or clamping the D and holding the C? Have you tried to use the TDDs (tiny diamond discs) to do your G? I either need to switch to your method or order some thinner burrs. It takes 2 large wires or 3 small wires to fill my G so it does not look funky. And trying to do a GW with 3 wires is quite a task.
My highest form of multitasking is chewing gum and walking so I understand your dilemma when trying to take a photo.
Good luck with your DD GW C.
Jim
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Post by mohs on Jun 17, 2012 18:07:12 GMT -5
 My double disc silicone carbide (dds/c) setup I'm sure you could go ts/c for even a wider G but at some point your bound to pick Pi wobble  mostly |
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