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Author Topic: MB concave build  (Read 1404 times)

Faceting Frank

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Re: MB concave build
« Reply #30 on: October 05, 2019, 03:49:51 PM »
I don’t know much about concave cutting attachments, but I do know the quill is going to have to travel in a perfectly vertical trajectory as you alter the angle. If it doesn’t then it will be moving to the left or right of centre as you alter the mast height.
 My mast is the same as Ultratech. But what I had to do to my machine to get the quill 90deg to the lap and allow me to cut the stone in the picture from 90 to 20 deg. Keeping all facets aligned without using the cheater, is to have an adjustment for the quill pivot, altering this by trial and error till I got it right.

« Last Edit: October 05, 2019, 09:04:45 PM by Faceting Frank »

FlashGP

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Re: MB concave build
« Reply #31 on: October 06, 2019, 09:10:17 AM »
Hi Frank,

Pretty much the same issue, but the cylindrical cutter on a concave cuter adds two more dimensions of error. 

With a flat lap on an ordinary faceting machine, the plane through which the quill pivots must be perpendicular to the top of the lap and the plane through which the stone sweeps across the lap must be parallel to the lap. 

The vertical quill pivot plane on the concave cutter must still be perpendicular to the top of the cutter, but it must also be in the same plane as the centre of the cutter as it travels back and forwards.  If it is parallel to that plane, then the facets will be off-set, that is when at 96, they may be cutting as if set to 2 or 94.  This is because the stone is no longer sitting on top of the cutter, but part way around its circumference.

If the mast is off-set (as in the GemMaster) and this is not compensated with the Quill positioning, the cuts will be tilted on the stone.  It's why you need to be able to adjust the position of the cutter relative to the quill so it is perfectly aligned.

regards
Gordon
Yours Sincerely
Flash (Gordon)

Faceting Frank

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Re: MB concave build
« Reply #32 on: October 06, 2019, 12:35:05 PM »
I’ve looked at the whole of this thread now and realise my comments would have already been thought over.
Don’t know if you guys could put a digital Vernier to use. I have one on my mast and use it to keep a record of its position on different rows of facets, or individual facets on some comp. stones. Allows me to get back to any facet with absolute confidence I’m spot on. Bought it at Hare & Forbes part number D667.

FlashGP

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Re: MB concave build
« Reply #33 on: October 08, 2019, 08:35:17 AM »
Hi Frank,

I use a Facetron on which the mast pivots.  The mast passes through the aluminium block that is the body of the faceting head.  As a result it would require a fair amount of engineering to mount a digital vernier. 

But because my protractor is permanently calibrated and runs off a crank and odometer, I have added a 1/100th degree scale besimide the tenth wheel.  This plus the dial indicator allows me to come back to the same height after changing angles.

Because I use laps of varying thickness, it is probably easier to use this setup than a digital vernier in the mast.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

FlashGP

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Re: MB concave build
« Reply #34 on: October 08, 2019, 08:38:38 AM »
Hi Makky,

About your reallignment issue with the concave cutter on the Gemmaster.

Thinking it through, you may have to add an adjustment to the pivot lock so you can compensate for the offset of the quill.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: MB concave build
« Reply #35 on: October 08, 2019, 10:21:52 PM »
I plan to cheat a bit flash if I have too and use the pivot of the concave cutter assembly to help with the alignment. :) Maybe i could make an adjustable 0 indicator.
I am about to start focusing on book volume two, I have 80 designs to work though, start test cutting and formatting and remove a few with the aim of having 60 really good designs I am happy with for book volume 2.So concave machine will be on hold of a bit until I get on top of the book. :)I am really happy with how most of the new designs render and can't wait to cut them  ;D
I'm thinking it will be better than volume 1.
CheersAndrew

FlashGP

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Re: MB concave build
« Reply #36 on: October 09, 2019, 12:08:45 AM »
No worries, I'm looking forward to seeing volume 2. 

I showed Volume 1 around or local facetors group meeting on Sunday, a number of the members were impressed.

regards
Flash
Yours Sincerely
Flash (Gordon)

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