Gem Grinder

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Joined
Jun 16, 2017
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Stanthorpe, QLD
Picked this up today, anyone know them or have a user manual? Needs a full rebuild, but once done, this can do so much.
1548665307_gemmmasta-gem-grinder.jpg
 
Well I think its an old Gemmasta ;) .. a very early Faceting Machine..... I think its around 1960ish or even earlier but could be a multi-purpose Machine... going by the Dops and the way the machine moves. Instead of tilting the stone as you do on a modern machine, with this one you move the lap back and forth...and swing the other half into the lap to give you your angles....
How to use? My guess is :
You put your dopped stone in the 'Head' on the right side and you can swing it into the Lap or saw blade on the left, well maybe not a saw blade but it could also Cut with a saw blade..... I think you would use a lap tho and the handle on the right would move the lap in and out so you are not working the same spot on the lap... And can be used as a Flat lapping Machine in a vertical stance, instead of a Horizontal Flat Lap too...
I will have a look through my old books... There could be something in there that will give you a definite answer...

LW....
1548674434_1548665307_gemmmasta-gem-grinder.jpg
 
Hey LW, it's called a Gem Grinder and was patented by Roy Arthur Gaerth back in 1970. It is for grinding rounds and Cabochons to very specific sizes so they can be set in standard sized findings.

Beautifully engineered gearing system so the length-width ratio can be varied.

Your markings are just about spot-on, the lap isn't flat though it's a sintered diamond edged wheel, guarantee is't going to be difficult finding replacements.

Back swing to the screw in stop is for the bevel edge, then the machine swings forward to create the dome.

There are a couple of bits I'm not sure about so hoping someone else has one and maybe a users manual to fill in the gaps.

Going to make an interesting winter project.

Picked it up from an Opal miner who was given it by an Opal cutter who passed a couple of years back.
 
Shows how much I know about Lapidary.... {) :eek: :( Glad you found that out...

Looking closer you can see a Cab still on the dopping stem :rolleyes: ... Few too many Bourbons today... Yeh Ha... Best I close the computer before I get into Trouble... O:)

LW...
 
We need to catch up as I have a heap of thin grinding wheels here that I got off an old fellow that I bought gear off a few years ago and don't know what you would use them for in Lapidary... So may-be?? they are what you need, im not sure...

LW.....
 
Jaros said:
Waddaya reckon-happy??

Youbetcha, lot more work to be done yet before I'll be happy to run the machine. Hopefully someone might come up with some more info as there are a couple of areas are not making sense. One is a cam, a secondary profiling cam which looks as though it creates the shape of the cab dome:
1548750537_dome-cam.jpg
I'm thinking there could be different profiles for different domes.
The other is an adjustable stop which doesn't seem to to touch anything.
1548750574_adjustable_stop.jpg

Looks like the knurled end un-screws and there is something that goes behind it and locks onto the flat sided piece beside the bearing.

Big question is what?
 
Oh I thought it was a Stone grinding wheel.. That's what I have here. 15 stone wheels of various sizes and grits... Didn't realise it has a 'lip' on the edge...
But I do have a brass one here that could be simular.(no lipped edge tho).. Never been used I think as there is no marks on it at all... I was going to use it as a base plate for my small flat lap that needs a re-build....

LW....
 
Dihusky said:
Picked this up today, anyone know them or have a user manual? Needs a full rebuild, but once done, this can do so much.https://www.prospectingaustralia.com/forum/img/member-images/10304/1548665307_gemmmasta-gem-grinder.jpg

Hi,
I have one of these cab cutting machines I bought in 1978 awesome for calibrated cabs...... from memory there was no manual .If you find one I'd love to get a copy....I lent my machine to my Dad and only got it back three years ago and I suspect I'm missing a few things....., my enquires led to Shell lap Adelaide who now make Gemmasta machines ( but not these ) but they still have some spares for these :) . cheers
 
mrjunkalot said:
Dihusky said:
Picked this up today, anyone know them or have a user manual? Needs a full rebuild, but once done, this can do so much.https://www.prospectingaustralia.com/forum/img/member-images/10304/1548665307_gemmmasta-gem-grinder.jpg

Hi,
I have one of these cab cutting machines I bought in 1978 awesome for calibrated cabs...... from memory there was no manual .If you find one I'd love to get a copy....I lent my machine to my Dad and only got it back three years ago and I suspect I'm missing a few things....., my enquires led to Shell lap Adelaide who now make Gemmasta machines ( but not these ) but they still have some spares for these :) . cheers

Wow, amazing.... kind of hoped something would appear eventually as there had to be someone out there who has or had come across these machines. They are an engineering marvel, hate to think what they cost back in the 70's

I am not sure if a manual is truly necessary, but would certainly be handy, I do have an old typed up chart detailing sizes, cams, hand wheel setting, roller number, 'back', thickness and 'crts', this is then divided into size for I assume round cabs, plus ovals with either high or low domes.

Happy to share this if you're interested.

What I'm chasing is the cams as I only have a #4
1553900127_4-cam.jpg


I'd love to get hold of the other 3 to make the set, if I can get the patterns then I can make them, likewise I don't have any of the rollers that fit the spindle on the rhs of the main drive. Having one cam gives me a starting point for making some more, but it will take a massive mount of experimentation to get them right. The rollers are a different matter though.

1553900284_roller-shaft.jpg


As I don't have one I have no starting point for making one, or a set. Based on the printed info I have, there are at least 3 different versions of the roller.

I haven't been in touch with Shell Lap as their website is now Gemcuts in Ballina who took over all the Gemmasta material, will have to give them a ring and see what they have.

Be great to share info if the info I have can be of help in any way.
 
I'm going to pull this out of storage in the next two weeks and I'll check those bits you're looking for and send you photos or cut templates for you if i can. Could you send me the chart you've got and any patent reference info to me at [email protected]
I use to have a jade and opal cutting factory , the grinder cut ovals, rds, cushion and with special cupped dop stick you could make beads by reversing 50% domes.
You can also make oval and round cylinders by cutting a hole in the otherside of the grind wheel face so you can then use it like a gem lathe. The machine also champhers a back bezel on cabs.
From memory the original cost in 1977 was $3,995 plus we had additional keyed brass dop sticks made. Have you got dops ?
Have you investigated if the inventor is still alive ? He was in Mile End area (?) Adelaide I think.
I did speak with Shell Lap three years ago and they inherited a lot of spares when they bought Gemmasta from the origin owner inc for our machine.
Look forward to collaborating .
Cheers,
Mike
 
Many Members with info on this Cab machine or others ...please email me... thanks Kiwi Ding
 
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