Jaegers 6" f/10 "GJD" OTA Construction - The Dew Shield (cutting groove around card stock -2)
 

Dew Shield being cut to proper size - 2. (Click to see an enlarged image.)

 
With the card stock still wrapped around the Dew Shield after shallow cutting along its edge, check out just how precise this method works in cutting the initial groove in the tubing. Now, the card stock can be removed to finish the process of cutting slowly around the circumference of the dew shield until the access section is cut away.