Turning Archive 2006
Robin Corell, Atascadero CA
>This is in response to david's post earlier in the week.
Thought I would throw out another option to how you are applying your sanding disc. When the cast metal disc is dynamically ballanced it is usually bolted to the hub and ballanced as a unit in many cases they are asymbled with pressed in dowels and with loctite used on the bolts. For this reason it is seldom a good idea to remove the disc from the hub. It is not a problem to remove the hub/disc from the motor.
Most patternshops use a special disc cement to apply paper backed discs to the steel or aluminium disc. it is rather expensive (aprox $30/qt) and requires a disposable brush. One qt will glue a dozen disc's on my 15" sander. The discs are removed easilly by lifting the edge with a knife. The paper peels off in one piece usually takeing the cement with it. the cement the remains is easily removed by rubbing with the palm of your hand. There are good directions on the side of the can but there is a bit of a learning curve for lining up the disc. you only get one shot. I have been able to remove the fouled cement from a missaligned disc and start over, and I have also ruined a disc when the cement would not come off. It is easiest to lower the table to expose the entire disc. line up one edge and then bring another point aproximately 90 degres along the circumfrence into contact with the edge of the disc. then roll it down along the middle try it dry first to get the hang of it.
Some guys like the PSA or spray on gunk like Supper 77. both aproaches work well and have shallow learning curves. I don't care for either because they both are dificult to remoeve and involve cleaning with mineral spirits and then removing the mineral spirits with acetone. too many fumes for my taste.
Either of these approaces will result in a sanding disc without holes near the center.
As you know most supplied sanding discs are a fraction larger in diameter. this allows for a slight missalignment and then the excess is trimmed. many people use a file to trim the edge. over time this will result in a rounded edge to the metal disc and will make it impossible to glue a disc all the way to the full diameter. the proper way to trim the disc is with the power off and use a piece of hard steel with a sharp 90 degree corner and aproach the corner of the disc at an angle and with a slight cutting action to shear the paper disc. this method will cause little or no wear over time to your metal disc.
I couldn't link to the exact page for the cement because it is a page in a pdf document and I don't know how to link it. The link is for Kindt-Collins index page. The cament is located under the pattern supplies heading and near the bottom is a catagory for abrasives. you can find a distributer near you by going to their home page.