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I want to sand/polish resin mold crafts. Most of the pieces I work with are around 2" on their widest sides. I am looking into a belt sander to avoid the manual process of sanding by hand. So far I only see two kinds of belt sanders:

  1. Flex shaft belt sanders, that range from 1/2" to 1" width sanding belts. This is not ideal, since it would result in uneven sanding.
  2. Table top belt sanders. It is easy enough to find 4" wide belt sanders like this, but these are extremely large bulk devices, and they offer no foot pedal.

Does there exist a device that can meet in the middle somewhere? Is it possible to jerry-rig a system using a flex shaft onto a table top belt sander, or attach a wider belt to flex shaft belt sander attachments?

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The basic issue is the required power. Belt sanders are designed for aggressive removal of material. The larger the surface area that is sanded, the more power it takes. At 1/2" to 1" wide belts, the required power is low enough that small motors can handle the job. Flexible shafts can also handle that (they have limited strength).

At 4" wide belts, you need big motors, and a heavy duty structure to support everything. You can find handheld 2" belt sanders that are within the power range that can be battery powered. You probably don't want to work with a belt the same size as your piece for the same reason you don't want to work with a smaller belt.

A reasonable compromise would be a 3" handheld belt sander that you secure in a fixture that you make or in a clamping work table. The motors for these are typically over 800 watts, which means they're normally plug-in, not battery-powered (although there are a few pricey professional-grade battery-powered ones). There's a selection of inexpensive consumer models at the big retailers.

When not in use, the sander is the size of a handheld power tool, so it's easy to find a storage place. The clamping work tables typically fold for storage, and are handy for a variety of uses (it is a general purpose work table, not a dedicated part of a sander). You could make a tabletop fixture for the sander that would be relatively compact. A 3" sander and fixture would be considerably smaller and lighter than a 4" tabletop sander.

I've seen videos of hobbyists who have made their own belt sander from wood and other available supplies that they power with a drill. A drill motor will have enough power for very light duty sanding, but any significant load is likely to damage it.

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  • +1 for the main answer and I would have given an other +1 if I could for the warning in the last bit, the likelyhood of damaging a drill in a home made machine if the load is too big.
    – Willeke
    Feb 6 at 11:05
  • thanks! This is good info, I hadnt thought to search for 3" sanders. One more question, resin is supposed to be more susceptible to heat, so would an orbital sander be a better idea? There is far less friction happening with an orbital sander. I imagine I can clamp either tool
    – andykais
    Feb 8 at 15:41
  • @andykais, the common resins are thermoset; they can be machined once cured, and heat accelerates the cure (although sufficient heat can damage them). An orbital sander will work (and be smaller). If the purpose is more in the nature of smoothing and polishing rather than shaping, they're less aggressive and would provide better control.
    – fixer1234
    Feb 8 at 18:58
  • Heat and orbital vs. belt sanders: the belt sander does a better job of transporting away material once it's been removed - and that material often gets hot when trapped as well as reducing the efficiency of the process. The belt also has a chance to cool when it's not in contact with the workpiece. Sanding can certainly scorch thermoset resins if you're not careful
    – Chris H
    Feb 15 at 15:23

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