Knife sharpening

[theo1961]

Hello all, I am going to begin sharpening my flexcut knives in a belt sander with a 1” x 30” leather belt from Surgi Sharp. The instructions from Flexcut is when using one of there strops, that you should hold the knife at a 15 degree angle. When I begin using the belt sander, should I still hold the knives at 15 degrees or should I lay them flat?

[Bob K.]

I'm not a knife maker or an expert on knife sharpening by any means but to me if you are using a leather belt that tells me you are stropping your knife and not sharpening or reshaping the blade. I would say you will probably want to still maintain the 15 degree angle. I'm sure someone here on this forum will correct me if I'm wrong.

[Brian T]

15* is fine if you are tuning up a wood carving tool with a bevel on only one side of the blade, like a crooked knife.

For a knife with a straight edge, bevelled on both sides, you need to lift the blade 7* - 8* on each side
to leave 15* or 16* in the middle as the total included bevel angle.

At the spine of a Flexcut blade, that's no more than the thickness of a dime.
I do the same for both Flexcut and Moor with nice results.

[pallin]

If the blade has a bevel already, raising the spine while working it on the belt sander will increase the bevel. If the bevel was correct to begin, it should be flat on the leather belt for honing. If the leather belt is soft and spongy, it will round the edge rather than hone it.

[theo1961]

My situation is, The knives are not damaged, I just want to bring my Flexcut knives back to razor sharpness. I’m still not quite clear on the method I should use to obtain that

[Randy]

If the cutting edge just needs to be refreshed the strop should do it. As pallin suggested make sure your belt firm. Let the belt do the work. You should not use a lot of pressure. With power sharpening or stropping it is easy to damage your edge.

[theo1961]

Thank you all so much for the advice, that clears things up for me

[Eddy-Smiles]

Be aware of the kind of stopping compound you use and the length of time you leave that knife on that belt. "A little goes a long way!" I use hard and soft buffing pads as recommended by Mac Profitt and Alan Goodman and it only takes a second to restore an edge on my favorite knife. Use the wrong compound and leave the knife too long on the strop and you'll use that blade up a lot faster than you want to.

[Dileon]

Be aware of the kind of stopping compound you use and the length of time you leave that knife on that belt. "A little goes a long way!" I use hard and soft buffing pads as recommended by Mac Profitt and Alan Goodman and it only takes a second to restore an edge on my favorite knife. Use the wrong compound and leave the knife too long on the strop and you'll use that blade up a lot faster than you want to.

I have taken interest in use the buff pads since I got alot of the materials with the lathe One question getting the compound to stick.....any comments? Next anymore advice or tips on using them?

[Brian T]

If your honing compound is in stick or lump form, smell it. The carrier/binder is commonly some sort of wax. Many have a really pleasant smell.
All waxes melt at or near 60C/150F. If they don't, it's plastic.

To charge a felt or paper wheel, or a leather belt. give it a good spin. There ought to be enough friction to melt the face of the stick and that should stay on the wheel.

The amount of pressure you apply should matter more than how much honing compound is on the belt/wheel/card.
Honing and polishing compounds are all abrasives, very fine (0.25 micron) as they may be for grit size
When you see black, that's the metal of your knife, like the silver in an old B&W photographic negative.

The lesson is yes, you should be able to power hone an edge in seconds.
By hand, on one of my cards with CrOx/AlOx, I'll guess 10 pull strokes of 8" each is plenty.

[theo1961]

I will be using the green compound on the leather belt and white compound on a buffing wheel. Robson Valley, if you start to see black on your belt, is that an indication of leaving it on the belt to long?

[Brian T]

The black is very finely divided metal particles. In this case, steel from your knife.
You have got to rub off some off that blade steel to straighten out the exact edge.
Under a microscope, you would see parts of the knife edge folded over like the flap on an envelope.
That stuff, you rub off in the honing process.
Easy does it. Test in your carving wood, decide if you have to hone more.

The Green is Chromium Oxide (may have some aluminum oxide mixed in it = OK.)
The white compound is straight aluminum oxide, very hard and slightly small nominal particle size than the CrOx.

It's easy to keep thinking that sooner or later, you will hone the entire blade away!
I can't see any changes in any of my blades of any kind in about 20 years or so.

Go visit your local farrier: ask to see a new crooked hoof knife
Then ask to see a used one from the junk box.
That is worn down.

[pallin]

I will be using the green compound on the leather belt and white compound on a buffing wheel. Robson Valley, if you start to see black on your belt, is that an indication of leaving it on the belt to long?

You will always get black particles as you use any compound. It does not mean you have kept the tool on the belt too long. If the tool gets too hot to touch - that's too long!

Just as a related comment - I hand hone my tools with compound on cardboard. It rarely takes more that six or eight strokes to restore the edge. If it needs more I start with six strokes on a piece of 800 grit wet-or-dry emery paper.

[theo1961]

Pallin, if you end up using the 800 grit emery cloth, do you use it wet or dry? And do you apply compound to that?

[Eddy-Smiles]

I have taken interest in use the buff pads since I got alot of the materials with the lathe One question getting the compound to stick.....any comments? Next anymore advice or tips on using them?

Dileon..... The compound for the buffing pads has a wax base which sticks, unlike the compound for the leather strop. But it still takes a second or so for the bar to heat up and the wheel to accept the compound. I apply new compound each time I use the wheel. I've bought the green compound from Smoky Mountain Wood Carvers; gray and white from Harbor Freight; and black from Highway Shine. I like the green as my go to compound but Helvie Knives touts their White bar. I have a hard coated buffing wheel and that what I use the black on and mostly just for stainless steel knives where it takes something more aggressive to put an edge on them.