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Rob Cosman's Diamond Stone: Premium

Original price $244.00 - Original price $244.00
Original price
$244.00 - $244.00
Current price $244.00
In stock
Full Description
Customer Reviews

I recommend and use 300 / 1000 grit, double-sided, diamond stones as an essential part of my tool sharpening method.  Our diamond stones use only high quality mono-crystalline man-made industrial diamonds permanently adhered by electroplating to a thick, precision milled, steel substrate.  Use the 300 side for flattening your water / ceramic sharpening stones and the 1000 side to establish your secondary bevel or your initial flattening grit.

We quality control test EVERY diamond stone we receive to determine if it's flatness is within our standard of being out of flat, either convex or concave, by no more than .004 (4 thousandths) of an inch.  Stones outside our standards are rejected. Diamond stones within our standards are further graded as "Standard" or "Premium" quality.

The difference between our standard and the premium version diamond stones is the level of flatness.  Diamond stones that test between .0016 and .004 (1.6 to 4 thousandths of an inch) out of perfectly flat, are graded as "standard."  Diamond stones that test between .0000 to .0015 (perfectly flat to 1.5 thousandths of an inch) out of perfectly flat are graded as "premium."  

Premium diamond stones are recommended for flattening the back of chisels and other applications where near perfect flatness is a must.  Standard diamond stones are recommend for routine sharpening of plane blades and chisel cutting edges and general sharpening uses.

Product details 

  • Precision milled, double-sided diamond stone 3" wide x 8" long.

  • Electroplated with Monocrystalline industrial diamonds.
  • Fine 1000 grit (5 micron) on one side and coarse 300 grit (50 micron) on the other.

  • Clearance channels on the coarse side produces a faster, cleaner cut.

  • Use the coarse side for flattening your water / ceramic sharpening stones and on your chisel and planes when you need some aggressive cutting action.

  • Use the fine side for sharpening your secondary bevel on plane blades and chisels and other edge tools. 

  • Comes complete with a non-slip mat.  

One-Time Break-in Procedure: The 300 grit side of our diamond stones requires a one time break-in procedure.  There is an excess layer of diamonds which needs to be removed before the surface is at its optimum. Break-in the stone by rubbing a piece of steel (a screw driver shaft, plane blade, etc.) over the entire surface of the 300 grit side for 1 minute.  Rinse and wipe off the diamond stone; it is now ready to use. Failure to break-in the 300-grit side can lead to cross-contamination of water stones. 


Customer Reviews

Based on 18 reviews
Joseph D.
Great products and service

I purchased a premium diamond stone. I am still learning how to sharpen. Highly recommend Cosman’s products. And I commend them for their commitment to military service members.

Ovidiu Stateina

I am very pleased with the quality of this diamond stone and the customer service!
It is not cheap, especially if you are just a hobbies woodworker like me, but if you can afford it it's totally worth the money.
Used it along with the Shapton 6000 and 16000 grit ceramic stones to sharpen a set of chisels. I have to say, I am totally new to sharpening and at first the whole idea felt a bit overwhelming, but after watching Rob's youtube videos and following his method I was able to get very good results. Thank you for making all these educational videos!
As for the customer service, I happened to order it during a sale event. Next day, after placing the order Rob himself called me. It was a really pleasant surprise and totally unexpected. He thank me for the order and let me know it will only be shipped the next day due to the amount of orders they received.

Brian Tooker
300/1000 diamond stone

prior to this purchase, i bought 2 of these Trend Diamond stone; one on Amazon and one at Woodcraft. both stones showed the same issue. the diamond grit on the 1000 side of both stones detached in long strips along both edges. this stone, purchased from Rob Cosman, has worked flawlessly. i am currently flattening the backs of a set of chisels and will be using this stone as well as some Shapton stones, to flatten and sharpen my chisel blades. i am very happy with this purchase. thank you.


Can’t wait for next order with 16000 grit stone to use


Can’t wait for next order with 16000 grit stone to use