Today I stated working on a jewelry box something I had not made in many years. I remembered I saved several boxes of sanding castings / patterns I made way back when in the early 2000's when I was making these boxes quite often. I located them and had a look after nearly 22 years.  

The jewelry boxes and humidors back then were constructed with profiles of some complexity using various router bits to make separate profile components and then assembling the components into one piece from several pieces  to obtain the profile I was looking for. This worked very well but created a problem specifically how to finely finish sand the profile without ruining it !
 
OK that was the problem how not to screw it up at finish sanding. I thought if I could mold a custom sanding block that matched the profile exactly I could maintain the finer deatil and get the finish I needed.
The Fix

 For every profile I would make several extra running inches . I then took a length of the profile usually 2 to 3 or 4 inches long squared it up on the ends and glued up a box around it. Please see the pics. The next step was to apply 2 or 3 coats of paste wax (Johnson’s Paste was around back then and it workrd great) to the boxed up profile.  Here comes the magic, from there simply make a casting using BONDO the auto body filler stuff. Simply fill the box with Bondo covering the complete profile within let it cure and pop it out of the mold. You can kind of see the BONDO  the light pink color stuff in the pics. When cured it is pretty hard and a perfect reverse of the profile. .
Square up the Bondo casting glue on a hardwood block to assist handling / holding and lay in some sandpaper.
The result was amazing, the profiles on the jewelry box sanded perfectly with all the details and sharp and crisp edges. 
If you have some similar projects that would be difficult to finish sand give this a try.
Please ask any questions.
Calabrese55

 

Thanks! Cool idea!!!

Excellent idea and tip Mike. Thanks for the visuals showing your process and end result. Helpful for current and future readers.