- Joined
- Nov 28, 2011
- Messages
- 288
I had posted the following in an earlier thread started by fitzo HERE - which has been moved by the moderators to "Whine & Cheese" I think it's a topic that merits some attention. Most mentions of CAMI/FEPA on bladeforums are in regards to sharpening, not blade making.
For me, the take-away from fitzo's original posting is not whether he should have looked more closely at the photos of the grinding belts before purchasing them, but rather that there is a marked difference between P and non-P belts and that the suppliers do not point this out to their customers. As if choosing abrasives was not complicated enough. I wonder how many makers are even aware of the P and non-P grading?
Here's a link to another chart and explanation of the differences. https://www.abrasiveresource.com/v/vspfiles/files/grit%20comparison.pdf
It states:
FEPA Grading: The majority of coated abrasives manufactured today use the FEPA standard (Federation of European Producers of Abrasives), otherwise known in the industry as “P” grading. Abrasives in the P scale are graded to higher tolerances than CAMI graded abrasives.
CAMI Grading: This grading standard is used exclusively by US manufacturers of coated abrasives, and is overseen by the Coated Abrasive Manufacturer’s Institute and the American National Standards Institute (ANSI). The CAMI-scale tolerates a wider range of grain sizes within the definition of the grit.
This site https://www.buehler.com/grinding-and-polishing-guide.php discusses FEPA/CAMI this way:
As with many standards, they are not mandatory and manufacturers can, and do, make some of their papers to different mean particle sizes than defined in these specifications. There is a philosophical difference in the two systems. ANSI/ CAMI papers use a wider particle size distribution (centered on the mean size) than FEPA papers. A broader size range allows cutting to begin faster at lower pressures than with a narrower size range, so less heat is generated and less damage results. However, the broader size range does produce a wider range of scratch depths; but, these should be removed by the next step in the preparation sequence. Generation of less damage to the structure is considered to be more important than the surface finish after a particular grinding step, as it is the residual damage in the specimen that may prevent us from seeing the true microstructure at the end of the preparation sequence.
From the above, it would seem CAMI graded belts are more appropriate for coarse grinding operations, and FEPA for finer operations.
The VSM ceramic belts sold by POPs (the ones that have the backside visible in the product photos) show only a grit number (without the letter "P") VSM is a German company that states on its website that it's a member of FEPA, but these ceramic belts are listed in CAMI grits. On the other hand, POPs VSM cork belts show a P1200 on the back, and are equivalent to somewhere between 600 and 700 grit on the CAMI scale.
Klingspor states "All KLINGSPOR coated abrasive products, with the exception of Alumina Zirconia and Ceramic Aluminum Oxide, are graded by grit size using the FEPA or P-grade scale".
Hermes also sells belts graded with a P-grading and without. On the POPs website, the backs of the Hermes CN 466Z belts are not visible....... according to Hermes they are not P-graded. The backs of the Hermes RB belts are visible on the POPs site and show a P-grading. The Hermes P-600 cork belts I have in my shop are between 360 and 400 grit CAMI.
Trugrit offers 3M belts that are P-graded and non P-graded with no distinction made between them on Trugrits listings.
I'm sure other sellers do the same.
So yes, the information is out there for us. It would be nice to get more clarity from the abrasive dealers, as we mostly buy from them and they sell from multiple manufacturers. But given the realities of the supply system, for now, it's left up to each of us to find our own clarity.
Saludos
J
For me, the take-away from fitzo's original posting is not whether he should have looked more closely at the photos of the grinding belts before purchasing them, but rather that there is a marked difference between P and non-P belts and that the suppliers do not point this out to their customers. As if choosing abrasives was not complicated enough. I wonder how many makers are even aware of the P and non-P grading?
Here's a link to another chart and explanation of the differences. https://www.abrasiveresource.com/v/vspfiles/files/grit%20comparison.pdf
It states:
FEPA Grading: The majority of coated abrasives manufactured today use the FEPA standard (Federation of European Producers of Abrasives), otherwise known in the industry as “P” grading. Abrasives in the P scale are graded to higher tolerances than CAMI graded abrasives.
CAMI Grading: This grading standard is used exclusively by US manufacturers of coated abrasives, and is overseen by the Coated Abrasive Manufacturer’s Institute and the American National Standards Institute (ANSI). The CAMI-scale tolerates a wider range of grain sizes within the definition of the grit.
This site https://www.buehler.com/grinding-and-polishing-guide.php discusses FEPA/CAMI this way:
As with many standards, they are not mandatory and manufacturers can, and do, make some of their papers to different mean particle sizes than defined in these specifications. There is a philosophical difference in the two systems. ANSI/ CAMI papers use a wider particle size distribution (centered on the mean size) than FEPA papers. A broader size range allows cutting to begin faster at lower pressures than with a narrower size range, so less heat is generated and less damage results. However, the broader size range does produce a wider range of scratch depths; but, these should be removed by the next step in the preparation sequence. Generation of less damage to the structure is considered to be more important than the surface finish after a particular grinding step, as it is the residual damage in the specimen that may prevent us from seeing the true microstructure at the end of the preparation sequence.
From the above, it would seem CAMI graded belts are more appropriate for coarse grinding operations, and FEPA for finer operations.
The VSM ceramic belts sold by POPs (the ones that have the backside visible in the product photos) show only a grit number (without the letter "P") VSM is a German company that states on its website that it's a member of FEPA, but these ceramic belts are listed in CAMI grits. On the other hand, POPs VSM cork belts show a P1200 on the back, and are equivalent to somewhere between 600 and 700 grit on the CAMI scale.
Klingspor states "All KLINGSPOR coated abrasive products, with the exception of Alumina Zirconia and Ceramic Aluminum Oxide, are graded by grit size using the FEPA or P-grade scale".
Hermes also sells belts graded with a P-grading and without. On the POPs website, the backs of the Hermes CN 466Z belts are not visible....... according to Hermes they are not P-graded. The backs of the Hermes RB belts are visible on the POPs site and show a P-grading. The Hermes P-600 cork belts I have in my shop are between 360 and 400 grit CAMI.
Trugrit offers 3M belts that are P-graded and non P-graded with no distinction made between them on Trugrits listings.
I'm sure other sellers do the same.
So yes, the information is out there for us. It would be nice to get more clarity from the abrasive dealers, as we mostly buy from them and they sell from multiple manufacturers. But given the realities of the supply system, for now, it's left up to each of us to find our own clarity.
Saludos
J
