How to set SRA after determining true vertical?

As I have said before and nobody pays any attention. Probably becuase they think I'm wrong. Your record could care less about the cutting edge angle. What you want is maximum contact with stylus and grove. if you are lucky this will occurr when the headshell is parallell with the record surface.

When that happens you can then use the catridge angle as a tone control rocking it back and forth by raising or lowering the back of the tonearm. vtf can also change this angle. the more down force the more the cantilever will deflect. Stereo seperation is affected by antiskate and azimuth.what you want there is the the stylus riding in the direct center of the grove. easier for linear arms.

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.

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.

Nsgarch- you make a convincing argument. your shovel and chisel anology could be true but they move in only one plane. the cutting lathe moves in two planes. I believe your analogy would be true if the cutting head were like a jackhammer titlted forward. Then each groove would be cut from the top with the resulting angle of the jackhammer. Not so when the cutting head is moving in two planes.

Like I said I definitely hold the minority opinion.
BTW thank you for such a gentlemanly rebuttal.

cutting in one plane would dig a hole. to make a 45 degree grooved trench you have to move in two planes n'est pas? maybe I stated it wrong.

I am thinking the cutter head acts more like a plow vibrating fom side to side. thus the record rotates under the cutting head as the head plows ahead vibrating either to the right or left, thus there is no downward cuttiing motion. that is why I prefer the vertical position.
I think I 've made enough empiracal arguments it's time to do some research.

A wrong theory carried to a ridiculous extreme.

I am still looking for an article or picture that demonstrates that angled cutting head produces an angled cut. Has the angled groove been measured? All I have ever read is that it was just assumed.

http://www.smartdev.com/LT/Align.htm. more drawings.

Doug- given that stylus rake angle is such a well accepted theory somebody must have done this already. With far more accuracy than I can. From what I have gathered so far the head is more like a plow than a knife. It cuts forward and to the side. The cutting head digs down into the vinyl cutting ahead and side to side. The master is rotating underneath the head.
To further complicate matters the cutting is now being heated. This means that there is some melting going on. The articles all swear by SRA again providing no proof.

Nsgarch- I found a picture of the groove. Results are inconclusive.
Doug-Just off the top of my head I might get similar results with a router.
I guess the burden of proof is on me.http://aolsearch.aol.com/aol/search?query=pictures+of+record+groove&invocationType=spelling&itaq=0.2.1.KQzKRxLUFAB&itaq=1.0.1.pictures+of+record+groove&itaq=2.1.1.I hope that takes you to a picture of record groove and compact disc digits. If not just type " pictures of a record groove" on your aol browser. Taken by elctron microscope.

See also, http://www.recordcollectorsguild.org

SRA is irrelavent. It is the position of the stylus in the groove that counts. The maufacturer designed the cartrridge to achieve that with the arm parrallel to the record surface. To the extent you use different forces and angles you may have to raise or lower the arme to restablish that angle.

Whoops! I've said all this before. I keep getting sucked in. Any way vdh's advice sort of proves my point. Think about it. He also had to make the call. If the cantilever is sort of a spring it will deflect under different loads (vtf). Thus if the range is 1.5 -2.2 grams. Then in setting the SRA he had to pick the load producing his optimum sra for that load and arm geometry.

I "believe" that all your are doing is "relocating" that point based on your different load and arm geometry and not duplicating the original SRA of each record. Of course it changes from record to record because record thickness again alters the arm geometry.

Perhaps Doug is right and we are approaching the same solution from a different direction.

http://recordcollectorsguild.org/index.php?name=Sections&req=viewarticle&artid=8&page=2
The Record Guild
I posted this before, but they have rebuilt there site. If you have the latest computer graphics, you can see magnificentt detail of record groove and stylus. This is the picture of the dead silver fish and fungus growiing in the record groove. Enjoy!
Gregadd