"Can I load this belt and expect to cut a primary bevel on AEBL ?" - Short answer - No.
Plain cloth belts are for charging with compound abrasives. Consider them an alternative to a buffing wheel.
They are usually charged with bar/stick type compound impregnated with fine grit or various polishes. I don't think you will find any with a coarse grit. I use them from time to time with black emery compound. That is the coarsest grade of compound I know of. Emery is for a pre-polishing step called "cutting", not a material removal step.
The second reason J-weight would be a problem for 80 grit is mechanics/physics. The larger grains won't "bend" around the idler wheel or waterfall edge as easily as finer grit. It will break the backing glue bond, and the grit will come off the belt quickly. This is why you don't see commercial J-weight coarse belts.
80-grit will fly off the belt almost immediately in any grinding attempt on a homemade belt. The way it is bonded on commercial belts is much stronger than any homemade glue attempt.
Belts are made in long rolls and cut and spliced to different sies later in the process. Making one up on an already spliced belt would add considerable problems in itself. Despite what you may see on YouTube, you really can't splice belts yourself at home. The glues used are very special and it is done on a specialized machine.
Here is part of an article by Klingspore that explains the process:
2. Maker Coat
The maker coat is the first layer of adhesive bonding that is applied to the backing. The purpose of the maker coat is to provide a seat for the grit that will be attached in the electrostatic coating process. It is what adheres the grit to the backing. Most of the bonding agents today are synthetic resins and are phenolic which ensures a sturdy, heat-resistant connection of the abrasive grit and the backing.
3. Electrostatic Coating
Electrostatic coating is a process in which a plate with a negative charge is placed above the backing (which has the maker coat applied), and a plate with a positive charge below a loose grain conveyer containing abrasive grit. The grit has been graded several times to obtain the appropriate size. This results in a separate charge being created between the two plates that pulls loose grit up from the conveyor and onto the backing in such a way that each abrasive grain is consistently oriented on the backing with a broad base against the backing and a sharp end pointing out. This is the most common method for coating backings with abrasives in use today.
There is another method of grain coating called gravity coating, which simply drops the grit through the use of gravity onto the backing without orienting it as the electrostatic method does. This method is still sometimes used today for coarser grits but would be most ineffective for any finishing grit. This process may be modified to alter how much grit is applied to the backing, determining whether a product is a closed coat, semi-open, or fully open coat.
This is done by inserting a filtering screen between the maker coat and the loose grit conveyor that will only allow 50 - 70% of the backing to be coated in grit.
4. Curing
After the maker coat has been applied and the electrostatically placed grit has been added, the material is run through curing ovens to ensure a good bond between the grit and the backing. You can have the best grit and backing in the world, but if they do not remain connected, the products will not be effective.
Curing oven times and temperatures vary depending on the types and sizes of grit, the backing, and the type of bonding agents used. Once this initial curing is completed, you are ready to add the second layer of adhesive bonding, which is the size coat.
5. Size Coat
The second layer of adhesive bonding, referred to as the size coat has two main purposes. The first is to tie the individual grains on the abrasive backing together to act as a unit instead of as individual grains. The other function of the size coat is to act as a heat shield for the grit. As previously discussed, most of the bonding agents in coated abrasives are phenolic resins, which after curing, are heat resistant.
Too much size coat or too little size coat can cause performance and finishing issues. Too much size coat and the grit won't be able to cut, instead creating a shiny effect on the abrasive's surface. It can often result in burning of both the abrasive and the workpiece. This is called glazing.
Too little and the abrasive grains won't act as a unit and will shed individually under pressure. Glazing and shedding are primary indicators that something may have gone wrong during the application of the size coat.
The application of the size coat is also where several optional steps may occur. These would include but not be limited to the addition of dyes, stearates, and lubricants. The size coat is a critical part of the making process that can have far-reaching effects on both the life and finishing properties of the coated abrasives.
6. Curing (Again)
After the size coat is applied, another curing step needs to be implemented to ensure the bonding agents cure completely.
