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Author Topic: Dopping with epoxy  (Read 913 times)

Faceting Frank

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Dopping with epoxy
« on: September 25, 2021, 04:41:03 PM »
After being sick of burning myself and balancing stones on top of hot waxed dops, only to have the stone fall off, I had to come up with something better.
So, this is it, accurately dopping stones with 5-minute epoxy. I had an old transfer jig I never used, so found a good use for it.
Bolted a bit of angle to it so I could fit two bolt stops, one under the stone and one behind. This will accurately dop any shape stone bar a triangle. After preforming the stone, in this case round, I measure its diameter. So, the formular for this is simple, Diameter of the stone minus the diameter of the dop, answer divided by two equals the distance between the dop and the bolt stop. Have plenty of washers lying around, so use a suitable thickness one to set the bolts in position.
Then set it up in the jig using some blue tack to keep the stone in position.
Transfer dopping is as usual and removing the unwanted dop is by holding the wanted dop with a wet tissue to protect the glue. Putting a weight on the dop to be removed and heating with a BBQ lighter.

geowork

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Re: Dopping with epoxy
« Reply #1 on: September 25, 2021, 08:22:56 PM »
Great idea and use of old equipment! A large diameter "target" dop can also be used to centre stones for dopping. Great for accurately dopping recuts.


Cheers
Bill

Wendy Purdie

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Re: Dopping with epoxy
« Reply #2 on: November 14, 2021, 10:19:27 AM »
Hi Bill,
Love the idea of a targeting dop, where did you buy this one from? Will it fit the Gemmasta transfer jig? Thank you Wendy Purdie

Bucket

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Re: Dopping with epoxy
« Reply #3 on: November 14, 2021, 05:08:38 PM »
Wendy, can you refresh my memory, does the Gemmaster have a pin, a flat section or a groove for locating it? I'm pretty sure there would be a targeting dop for them, check with Gem Cuts in Ballina, they have a website but a phone call might be easier. They are the manufacturer of the Gemmaster now. Welcome to the website too!
Common sense isn't exactly common

Rusted

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Re: Dopping with epoxy
« Reply #4 on: November 15, 2021, 07:37:59 AM »
Gemmasta have a pin.

geowork

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Re: Dopping with epoxy
« Reply #5 on: November 15, 2021, 09:09:03 AM »
Wendy,
My old gemmasta has a wide flat-faced dop. But it is the concentric grooves which do the trick. Gemcuts may be able to do that. The target dop pictured was made by Horst Ricker (Rubyvale) for my Hall. VJ will make up a similar 1/4" target dop that can be used in a gemmasta, and I have one from them.

All the best,
Bill

RoughCreations

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Re: Dopping with epoxy
« Reply #6 on: November 15, 2021, 09:24:04 AM »
FWIW, the standard Facetron target dop, pictured below, is 1/4" with a flat. They can be found online for purchase.



RC
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FlashGP

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Re: Dopping with epoxy
« Reply #7 on: November 21, 2021, 04:20:26 PM »
I'm not sure if I have mentioned it on this forum, but I recently experimented with removing stones from the epoxy on my dop using hot water and have adopted it as my preferred method because it saves me going to the workshop to fire up the metho burner late at night.


I just fill a cup from the hot water dispenser (98 degrees C) and soak the dop and stone in it for a couple of minutes.  This softens the epoxy enough to cause it to let go of the stone.


It gives me better control over the heat than a flame.


regards
Gordon
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: Dopping with epoxy
« Reply #8 on: November 22, 2021, 08:02:05 AM »
Hot water is only good for some epoxies. Dextone needs more heat. I heat the dop shaft with a lighter and keep the flame off the stone. I then soak in acetone to remove any left on the stone.
MB


Bucket

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Re: Dopping with epoxy
« Reply #9 on: November 22, 2021, 09:50:14 AM »
Thanks for the info Gordon, I use the same method as MakkyBrown, I used to try peeling off the excess with my fingernails while it was still warm but it tends to destroy your nails and you've got to be quick as it cools rapidly!
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FlashGP

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Re: Dopping with epoxy
« Reply #10 on: December 14, 2021, 08:10:22 AM »
Makky,


Good to know that Dextone uses more heat, I’ll have to get some more for cutting sapphire and silicone carbide (moisonite). 


I am currently using JB Kwik, so clearly it lets go at a lower temperature than Dextone.


Regards
Gordon
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: Dopping with epoxy
« Reply #11 on: December 14, 2021, 01:21:13 PM »
I cure the dextone in an oven at about 40 degreesC till pretty much rock hard.  I cook my transfer jig and have a cupper. Strongest and most reliable epoxy I've used.  You want to get the correct one though. You want the 5min Metal epoxy not the home one.
MB
« Last Edit: December 14, 2021, 01:23:02 PM by MakkyBrown »

Ghost

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Re: Dopping with epoxy
« Reply #12 on: December 31, 2021, 11:39:37 AM »
Since the disappearance of Tite-On many years ago, I have had enormous success with Epifill, by AkzoNobel.
This is a 2-part epoxy resin, in the ratio of 2 parts filler to 1 part hardener.
It is readily available from ships chandlers, as it is used to repair fibreglass hulls.
I think Gemcuts used to carry it, but do not appear to now.
I strongly recommend this product to anyone seeking a better dopping system to the one they are currently using.
Only problem is it has a 24 hour, or overnight, cure time.
Try it and see.
Cheers.    Ghost.

Bucket

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Re: Dopping with epoxy
« Reply #13 on: December 31, 2021, 01:00:26 PM »
I've been using alternatives, JB Weld is the one I would recommend. There was another I used that I purchased from Aussie Sapphire but can't remember the name, it was also a two part epoxy but was clear when set. That worked well. I still have some Tite On, obtained some from a gem show a while ago, but when this has gone, I'll go back to the JB Weld. Haven't used Dextone, Makky, how did you find an oven that goes down to 40C?, ours only goes down to around 80 ish.
Common sense isn't exactly common

MakkyBrown

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Re: Dopping with epoxy
« Reply #14 on: January 09, 2022, 05:28:07 PM »
It has a perhaps old fashioned thermostat and knob.  I should really get a smaller toaster oven.
JB Weld is ok but Dextone sets harder. I remember having stones come off with JB. I've tried a fair few and I think Dextone is the best. Especially if you are generating heat when you polish. Once you have used the tubes for a bit it is nice and thick and hard to squeeze out of the tubes. The first bit is a bit runny but after that good.Googled Dextone, looks like all the Australian lapidary supply places are selling it except Gemcuts.Cut and Slice say ready to facet in 10minutes but no way I'd do that with any 5minute epoxy.

 

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