Small pieces are often the most awkward to sand. A loose strip of sandpaper may seem convenient, but it can fold, slip or simply follow the movement of the fingers. This makes it harder to keep a surface flat, produce a consistent chamfer or follow a controlled curve.
I originally designed a compact flat sandpaper holder to give a 30 mm abrasive strip a firm, predictable backing. I have now added a second holder with a long, gradual convex face. The fastening idea is shared, but the two tools serve different purposes.
Photograph: the flat and rounded holders show how changing the backing shape changes the sanding task.
One fastening idea, two sanding surfaces
Both holders use a removable rear clamp and a large printed thumb screw. The abrasive strip passes over the working face and is held at the rear. When it wears out, the screw can be loosened and the strip replaced.
The important design decision is the form beneath the abrasive. Sandpaper alone is flexible; the holder controls how that flexibility is used.
The flat holder: keeping flat work flat
The original holder has a rigid flat backing and an 80 x 30 mm footprint. It is useful for small flat faces, controlled chamfers and edge refinement where the intention is to preserve a straight or planar surface.
With loose sandpaper, fingertip pressure tends to concentrate in small areas. The paper can also curl around an edge and round it unintentionally. A flat holder spreads pressure over a defined face and gives the hand a more stable reference.
Photograph: the original flat holder assembled with a 30 mm abrasive strip.
For chamfering, hold the work securely, mark a guide line and maintain a steady angle. Light, counted strokes make matching edges easier to compare. The tool improves control, but the accuracy still depends on the user's judgement.
The rounded holder: following gradual inside curves
The second holder replaces the flat working face with a long convex profile. It is intended for broad concave surfaces, shallow inside curves and gradual transitions that a flat block cannot follow. Its narrow nose can approach tighter areas, while the wider part of the curve provides a larger sanding surface.
Photograph: the side profile reveals the gradual convex face and narrow nose of the rounded holder.
This is a useful lesson in matching a tool to the geometry of the intended result. A flat block helps preserve flatness. A curved form supports the abrasive while allowing it to contact a concave workpiece more evenly. Neither shape is universally better; each is selected for a different outcome.
Photograph: the assembled rounded holder, rear cap and hand-tightened printed screw.
A shared clamping system
The rounded holder uses the same custom printed screw interface as the flat design. Its main body, rear cap and thumb screw are separate parts, making the clamping action visible and easy to understand.
Photograph: the rounded body, removable rear cap and matching thumb screw separated for assembly.
Both holders accept 30 mm-wide strips. About 175 mm is a sensible starting length; fit the strip, confirm its path and then trim if required. Tighten the screw by hand only. The thread is a matched printed pair and is not intended for a standard metal M10 fastener.
Photograph: comparing the compact flat holder with the longer rounded profile.
Printing considerations
The flat holder is supplied in support-free STL orientations and includes a thread-fit coupon. Printing the coupon and screw first allows the thread fit to be checked before the complete tool is made.
The rounded body needs selective removable support beneath the rear retaining rails. The cap and screw print without support. A prepared Bambu Lab P1S 3MF is included with the download. Its slicer estimate is approximately 1 hour 58 minutes and 40.25 g of filament, including purge and support; actual results will vary with printer, material and settings.
CAD view: the rounded holder body and cap measure 80 x 30 x 30 mm, with an 88 mm overall length including the screw.
Slicer evidence: selective support is confined to the rear retaining rails.
The flat holder has been physically printed, assembled and function-tested in PLA on a Bambu Lab P1S with a 0.4 mm nozzle. The supplied photographs confirm that the rounded holder has also been printed and assembled, and its 3MF has passed slicer checks. Its sanding performance, paper retention, support-removal quality and durability still need further physical evaluation.
Sand effectively and safely
Start with a grit suited to the amount of material that must be removed, then move progressively to finer grits. Test the chosen holder on scrap before working on the project. Secure small workpieces, wear appropriate eye and dust protection and stop using any printed part that cracks or allows the abrasive to slip. PLA can soften in high heat, so do not leave the tool in a hot vehicle or near heat-producing machinery.
The files are available separately for each holder, or together as a discounted set:
Download the Flat or Rounded 3D-Printable Sandpaper Holder on Gumroad
A simple holder does not replace skill. It gives the hand a backing shape that makes the intended result easier to judge and repeat. The flat and rounded versions show how one small change in form can produce two distinct workshop tools.
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