Belt Sander Sharpening Using the Platen

[me2]

Most people recommend not using the platen and sharpening on the unsupported area of of the belt. I did it this way for years. Just the other day, on a whim, I thought I'd try it with the platen on a HF 1x30 sander. I used a Klingspor 320 grit belt and sharpened a cheap 2 blade trapper from Lowes. It worked really well, I must say. The blade does heat up easier, but its not much trouble to control with light pressure and keeping the blade moving. Does anyone else do it this way? It seems to give me more control, but only when using the X weight cloth belts from Klingspor. The Gator Grit belts I bought at Lowes have a hump in the middle that doesnt flatten out even when it goes over the platen. These I find quite difficult to control. they are not as thick or stiff as the Klingspor belts. So, it seems than with heavier cloth belts, the platen method gives as good or better results for me. I'll try again this weekend, when I take a nick out of the cheap trapper.

 

[Greg]

On the most basic level sharpening is quite simple. It's just getting one side of the blade to meet the other at a pre-determined angle, and then refining the grinding on each side to the degree that works for you.

Practically speaking, if you are getting results you want, you are doing it correctly.

Greg

 

[raythebigfoot]

I think it just depends on whether you want the convex edge or not. The reason most people use the slack part is because it will give you a convex edge while using the platen will give you flat edge bevels. Either can get really sharp I think it's just personal preference.

 

[LedSled]

Working on-platen has always given me a rough ride, but one compromise that works is to raise the platen, and work just off the end. You don't get the pounding from the belt seam joint, but still get some platen support.

Ditto on me2's choosiness with belts. I favor 3M's mylar belts for their smoother seams. Cloth-backed belts can deliver quite a thump.

 

[me2]

The two smaller wheels on the Harbor Freight sander are not flat on the surface the belt travels on. I think this, in combination with the cheaper, thinner belts, causes the belt to retain the dome shape of the last wheel before the platen, so that one must use considerable pressure against the platen to flatten it out. I wonder if the mylar belts from Lee Valley Tools would do this. The extra pressure in the center of the belt makes for uneven grinding, or I'm just blaming my lack of skill on the belt. The heavier weight belts make grinding much more consistent. I sharpened a wharncliffe on the Gator Grit belts and the edge was wavy and the tip turned up. I filed that off (I made the knife, so no worries about damage) and tried again with a coarser, but heavier 40 grit ZrO belt and the edge was perfectly (by eye) straight.

The convex edge is easier to do repeatably for me. If I want a consistent finish, I use the convex. If you're off by 1 or 2 degrees on the platen, the next grit will not polish it out unless you really take off quite a bit.

I must be using relatively light pressure, or I've just come to ignore the bumping caused by the belt, but it doesnt seem to bother me when sharpening.

 

[Bill DeShivs]

A good 400 grit SIC belt is about all you need to sharpen. You can use graphite material available at knifemakers supply houses to pad the platen without giving it too much give.
Bill

 

[Patrickknives]

I do the same with a slack belt, I took the platen off. I then us a leather belt with chromium oxide to get it really sharp. Has good edge retention as well.

 

[Ben Dover]

I think it just depends on whether you want the convex edge or not. The reason most people use the slack part is because it will give you a convex edge while using the platen will give you flat edge bevels. Either can get really sharp I think it's just personal preference.

Agreed!:thumbup:

I've tried it both ways, and with an angle guide. All three methods worked well.

But since I prefer a convex edge, I use the slack portion of the belt.