How to set SRA after determining true vertical?

what's important then is the angle of the stylus not the angle of the cantilever. the stylus should be perpindicular to the rcord surface. If you took an xy graph and placed it on the record surface and placed the stylus at 0,0 or dead center and measured the angle in a 360 degree rotation you want 0 degree deviation all the way around.

Take a nail and dirve it into a board at a 90 degree angle about 1" from the end. You will see that the nail will be perpindicular to the surface. Now lift the end of the board 20 degrees. the nail is no longer at 90 degrees. you have two choices either bend the end of board 20 degrees or drive the nail in at 70 dgrees to compensate.

The cartridge and arm manufacturer do this for you as best they can. There are two variables they can't account for vtf and record thickeness. those two things must be accounted for by the end user. It might be easier if you chose the same cartrdge tonearm and turntable as the cartridge designer used.

Once you determinde the the arm is level by making sure the height of the arm is the same at the stylus, midlle and pivot hopefully the stylus is now perpindicular to the recocrd surface. You should be getting maximum contact with the stylus and grove as the cartridge manufacturer intended. My sme 4 provides a line through the middle of the arm for this purpose. You can then simply lower or raise the arm for different record thickness. Of course you should determine vtf before you finalize this process.

One additional variable is the mounting of the needle on the cantilever. If you examine a number of cartridges head on, you will find that the needles are not all set perfectly perpendicular to the cantilever or the headshell. Errors can be up to 3-4 deg. This is another reason why getting the azimuth and SRA right is not as simple as making the headshell perpendicular to the platter and leveling the arm etc. For azimuth, I would assume it is more important for the needle to be perpendicual to the record in the grove, than for the headshell to be parallel to the record surface. Anyone have any experience with this as well?

Zargon-the thrust of my argument is that SRA should be used to make the stylus perpindicular to the groove or record surface not necessarily mimmicking the stylus cutting head.
If I get you agree to that,I'm satisfied. How you get there is not that important. That will get you maximum groove contact and that is what you paid for.

I was just cautioning those who might not be sensitive to needle mounting variations. Their existence serves to strenghten the need to get SRA and azimuth close, and then make small adjustments either way while listening for the optimum setting. I really have no knowledge or opinion on whether the SRA should be vertical or 1-2 deg. forward, as Doug suggests. In my single case, it appears to end up vertical, but that is only one TT setup.

If you have a spherical stylus or even an elliptical sytlus, then the actual SRA is not too critical because whether the stylus is vertical, or leaning (less than a degree) slightly forward or backward, the very rounded tip is going to fit in the groove more or less the same way in all cases.

Such is not so for (the more common today) "micro-ridge" type styli, pioneered by Shibata and van den Hul. These styli are shaped a bit like a spade shovel, broad across the groove and thinner front to back. Their long edges touch the groove on each side, in a line running more or less from top to bottom.

The cutter head is VERY spade-shaped -- a chisel actually. It is not vertical either -- never has been, even with 78s. Why? Because if it were vertical, the cuttings it produces would jam between the head and the groove and ruin the master. Instead it is tilted forward (at the top, just like you'd do with a wood chisel) so that the cuttings keep "peeling" off and out of the way.

Therefore the "wiggles" the cutter cuts into the groove are all "leaning" forward as well as wiggling side to side.

If you have a "cutter-shaped" stylus (micro-ridge) and you want it to make the best contact or "fit" with the groove, it has to be tilted forward so that its edges match the forward-leaning groove wiggles. This angle of tilt is called the Stylus Rake Angle, or SRA. It is usually between 1 and 2 degrees for most recordings. But as Doug already pointed out, there is no actual standard, and cutting lath operators have some leeway in how they want to adjust the head for a particular recording, or perhaps use with certain brands of blank masters.

This is why I recommend adjusting the SRA to just under 1.5 degrees. Then, if you have a tonearm that's easy to raise or lower, you can "fine tune" the SRA for a given record -- increasing it for a thicker record, for example, or decreasing it if your ears tell you that maybe the lathe operator set the cutter closer to 1 degree.

A "vertical" setting would never do for a micro-ridge type stylus, because the edges of the "spade" would be straight up-and-down, and would actually scrape across the tilted wiggles instead of fitting into them.