As noted in my previous post, many spearheads come from the factor with a coarsely ground and blackened finish. This may be a cost-saving measure, but it's rather unappealing, especially if other your other steel items are already polished. Here I'm going to try to give a better finish to the AntiqueCraftsShop javelin heads.
I'm starting it on a mini belt sander I recently got on eBay. Sanding belts used for metal quickly acquire a smooth feel that belies the actual grit (size gradient of the sand) and are permeated with fine metal dust, so they should be kept separate from those used for wood and other materials.
The slightly hollow-ground faces can be sanded with a slow back-and-forth movement over an axle. If they were a flat diamond grind, I would press the faces against the belt where it runs over the supporting metal shelf. (This can be done to thin down the secondary bevels, though, since the angle needed to do so means the medial ridge is well clear of the belt.) Care is needed at this stage not to mess up the medial ridge. Once it's done, I turn the edges parallel to the belt sander to clean up any hints of unevenness created during this step.
Safety notes: For some reason this sander's belt is set up to move toward the motor and up from the sanding ledge. Also, of course, I am only holding the spearhead in one hand to snap the photo; you should always hold anything you are sanding in two hands whenever it's in contact with the belt, not only for safety but also because holding it in one hand often just doesn't work. And, of course, wear safety goggles whenever using any power tools that grind, cut or drill. I like chemical splash goggles that wrap against the face, making sure no metal fragments can get in my eyes again.
Sanding on top of the shelf allows you to press down hard on flat or convex surfaces, useful when trying to get rid of deep pits and grind marks. Moving convex surfaces to the gap between the axle and shelf allows the belt to wrap slightly around the surface, giving a more even finish.
After polishing to 60 (top), 150 (middle) and 600 grit.
Some of the sandpapers used to give the final hand polish. For this step I am tending to wrap the sandpaper around the back of one finger and use the other hand to rub the spear across it, following the alignment of the the scratches created by the belt sander. With the blade faces, it's very difficult to follow the sander's marks. I tend to instead just pinch the paper around the faces with my fingertips and rub the paper parallel to the blade; much easier, though not as effective.
The finished spearheads both illustrate the importance of using as many grades of grit as possible. Each grade is able to remove grind marks from a slightly coarser grit, while creating new marks of its own, until you're using a grit so fine that its marks are undetectable to the eye (achieving the so-called mirror polish). The spearhead on the left was initially polished with the 600-grit belt before moving on to finer grades of paper for hand-polishing. As a result, it still has lots of grind marks and pits with black scale that the belt was unable to reach or remove. The one on the right, which started on a 60-grit belt, has almost none of the factory marks left, but the jump from 150 to 600-grit left lots of marks from the 150-grit that the 600-grit belt didn't deal with. These are visible not as black scratches but as bright, sparkly ones. I'm not sure which one I dislike more. Either way, the conclusion is clear: I need to buy more stuff.
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