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 Post subject: Mandrel specifications for concave faceting machines
PostPosted: Fri Sep 01, 2017 12:37 pm 
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I would like to offer owners of concave facet machines plated diamond mandrels. I lack first-hand information on the desired diameters of the cutting surfaces, lengths of the cutting surfaces and the total length of the mandrel.
Any owners of these machines please feel free to post your specifications in this thread.

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 Post subject: Re: Mandrel specifications for concave faceting machines
PostPosted: Fri Sep 01, 2017 3:13 pm 
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I use mostly 8mm and 13mm cutting diameters. The length of the cutting surface is 1.5" and the whole mandrel is 3". Shaft diameter is 0.2493"
A 0.2510 shaft will not fit in the UT Fantasy machine.

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 Post subject: Re: Mandrel specifications for concave faceting machines
PostPosted: Fri Sep 01, 2017 6:07 pm 
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Precision Gem wrote:
I use mostly 8mm and 13mm cutting diameters. The length of the cutting surface is 1.5" and the whole mandrel is 3". Shaft diameter is 0.2493"
A 0.2510 shaft will not fit in the UT Fantasy machine.

Gene,
O.K. so, can the shaft be 6.0 mm diameter?
I noted 8 mm. and 13 mm. cutting surface diameters.
Do you have a preference for grit size?

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 Post subject: Re: Mandrel specifications for concave faceting machines
PostPosted: Fri Sep 01, 2017 11:51 pm 
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I think 6mm may be too sloppy.

I would like 1200 sintered type. Normally the amount of actually cutting is very small. The finest mandrill I have is a 600, and for me it’s too rough, takes too long to polish out the deep marks.

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 Post subject: Re: Mandrel specifications for concave faceting machines
PostPosted: Sun Sep 03, 2017 2:23 pm 
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Precision Gem wrote:
I think 6mm may be too sloppy.

I would like 1200 sintered type. Normally the amount of actually cutting is very small. The finest mandrill I have is a 600, and for me it’s too rough, takes too long to polish out the deep marks.


Gene,
Yes, 600 mesh (32 micron nominal) is a stock removal grit.
The collets for 1/4 inch shafts will accept 6.0-6.5 mm and no slop exists with such collets.
The downside of sintered mandrels, and I own one, is that as you dress it, the diameter decreases. You discard plated diamond mandrels after the diamond layer wears down so that the diameter specification changes little over the life of the tool.
If you like 1200 mesh, which is a 16 micron nominal grit, you would probably like the 12 micron nominal grit which I use in my 8 & over sintered diamond wheels: http://adamasfacet.com/sintered.html
The subsurface damage is less than 1200 mesh and the surface finish is a little better.
Best regards,
Tom

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