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Author Topic: belt sander knife sharpening  (Read 448 times)
zahc
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« on: October 12, 2017, 07:00:40 PM »

I saw the threads about the motorized sharpening and decided I should build an angle jig for the 4x36 belt sander I already have.


What grit belts do I need? it's hard to find anything finer than 800. I can finish on my sharpmaker.
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Regolith
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« Reply #1 on: October 12, 2017, 08:28:53 PM »

The belts that my Worksharp knife sharpener came with are 80, 220, and 6000 grit.  The 80 is a bit too aggressive for knives unless you're planning on removing a lot of metal, and I think the 6000 is a bit worthless. I suppose it's supposed to be a bit like a leather strop, but jumping from 220 to 6000 doesn't seem to work all that well. Personally, I'd want 220, 400, and 800.
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sumpnz
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« Reply #2 on: October 12, 2017, 08:44:08 PM »

For my waterstones I have 800, 1000, 4000 and 6000 grits.  For a knife that's really dull, or nicked it can take a while at 800gr to work out the edge.  Though once I'm happy at 800 it's pretty quick to go through the rest and get a scary sharp blade with a shiny polish from the 6000 grit stone.

If it was me, I'd go up to 800 on the belt sander and then switch to the water stones to finish the job.
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Nick1911
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« Reply #3 on: October 12, 2017, 09:34:17 PM »

General rule, double the grit with easy step finer.

Where you start depends on how much material you need to remove.
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griz
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« Reply #4 on: October 13, 2017, 02:21:17 AM »

I started using a Harbor Freight 1X30 and have been happy with the results.  Even 220 is on the coarse side for anything except garden tools or abused edges.  I went online to get finer grits and a leather belt to finish with.  There seems to be a lack of consistency in labeling between various brands, so I won't make any specific recommendations.  But it did amaze me that the finer belts were so smooth it was hard to imagine them being abrasive at all. 
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mtnbkr
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« Reply #5 on: October 13, 2017, 02:49:19 AM »

But it did amaze me that the finer belts were so smooth it was hard to imagine them being abrasive at all. 

On my WorkSharp tool, the finer grits feel more like slightly-rough paper than an abrasive media.

Chris
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Mannlicher
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« Reply #6 on: October 15, 2017, 01:08:38 PM »

the problem with belt sanders for knife sharpening  is that with just a slight miscalculation or slip, you can remove a lot of metal that you really did not want to do.  Yes, experts, and there may indeed be some of those here, can do fine and exacting work with a belt, but most folks just don't have the skill level or experience. 
I use an EdgePro Apex system.  It's slower, but I don't ruin my steel with it by accident.   It's what works for me. 
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230RN
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« Reply #7 on: October 18, 2017, 10:15:53 AM »

The other problem with any high speed removal is that if you are throwing sparks, you are heating micro-areas of the edge above heat-treating temps.  My personal attitude is that the business of keeping stones and stuff wet is not so much to remove particle clogging, but to hold down those micro-temperatures.

The goal is to get a zero-thickness edge without heating any part of that edge.  And it's real easy to locally overheat something with near-zero thickness, even if you're not actually throwing visible sparks.

Let the objections to this theory begin.

Terry
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