Large Batch Profile Sanding

02 09 2021

A craftsperson uses a flap sander to sand molding

In our previous blog post, Update Your Profile Sanding, we shared some ideas for making custom shaped sanding pads for finishing moldings, trim work and other profiles. These card, foam and body putty tricks are all well suited to hand sanding. But if you have a batch of moldings to finish hand work may be too slow. The foam and putty methods can be adapted to power sanding, but only with an inline stroke sander. The movement of the sanding pad must follow the line of the profile. Orbital sanders just won’t work. 

A completed shop-built flap sander

Flap sanders can be very effective. The flap sander we built in previous blog posts (Flap Sander Pt 1 and Flap Sander Pt 2) uses Cloth Shop Roll stock to create the flap sanding action. With a little modification, this flap sander can be highly effective at sanding all sorts of profiles, getting into the low areas without damaging the high spots. It is all in the treatment of the sanding roll sections once they are locked into the sander.

A shop-built flap sander mounted to a drill

As shown, the flap sander uses 1” wide Cloth Shop Roll, and while it is flexible, it would still tend to sand the high spots of a profile without bending well into the low areas. This will distort the profile. This issue can be solved by cutting the tips of all the roll ends into thinner strips. Simply cut from the end straight along the length of the strip to make equal “fingers” about 1/8” wide. These thin fingers will now be free to sand as deep or as shallow as needed along the molding. 

A craftsman cuts fingers into the sanding flaps on a flap sander

Mounting flap sander in a drill, or even in a drill press, will allow for sanding lengths of trim or moldings fairly quickly. And you can control the RPM of the sander, the feed rate between sander and stock as well as the grit of the Cloth Shop Roll being used. Admittedly, using a flap sander is not as efficient as a dedicated machine, but it is far less of an investment for shops that only do this task occasionally.

For instructions on how to build your own flap sander, visit our previous blog posts Flap Sander Pt 1 and Flap Sander Pt 2.