What type stone is this?

[jdrichard]

Used this stone to do the final finish on a balance staff pivot i just completed(hairspring side only...).

 

 

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[Marc]

Looks like a hard Arkansas to me. Hard Arkansas stone is a form of Novaculite which is a microcrystaline quartz.

It is an excellent natural whet stone and is used for the final touching up on your gravers (assuming HSS, not sure how it would perform on tungsten).

[jdrichard]

I used it to reduce the staff pivot size and it did a great job polishing the pivot. Of course i will not know until i finish the other half and install the balance, hairspring and roller. I may jacot the final staff and use my burnishing tool.


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[jdrichard]

Looks like a hard Arkansas to me. Hard Arkansas stone is a form of Novaculite which is a microcrystaline quartz.
It is an excellent natural whet stone and is used for the final touching up on your gravers (assuming HSS, not sure how it would perform on tungsten).

Replied above


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[oldhippy]

Thats an Arkansas stone. I had a block for tidying screw driver blades and gravers, one like yours for pivot work and a long triangle shape also for pivot work. Just add a spot of oil for best resaults. They will work on tungsten.

[jdrichard]

Thats an Arkansas stone. I had a block for tidying screw driver blades and gravers, one like yours for pivot work and a long triangle shape also for pivot work. Just add a spot of oil for best resaults. They will work on tungsten.

Hey, thanks. It does a great job reducing the pivot size.


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[mhorlogerie]

Translucent Arkansas 

[jdrichard]

After i use this stone do on need to finish up with a burnisher


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[jdrichard]

After i use this stone do on need to finish up with a burnisher


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[oldhippy]

1 hour ago, jdrichard said:

After i use this stone do on need to finish up with a burnisher


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Yes you should to take out any marks that have been left.

Edited February 22, 2018 by oldhippy

[jdrichard]

Yes you should to take out any marks that have been left.

Thanks


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[khunter]

Burnishing should be the last step, removes the marks, takes it down to the final size, and further hardens the pivot. A jacot tool is just the thing for this.....