How do YOU tell when you've raised a burr, and other questions

[Starfish]

Greetings all -

I started out the freehand learning experience last night, and ran into a couple of questions. I am starting out with a Victorinox Soldier SAK and using a DMT Diasharp coarse and fine stone. I have measured the blade thickness and width, and used the edge sharpening calculator to determine the proper height at which to raise the spine in order to achieve a 15 degree edge with 20 degree microbevel. I used a black Sharpie to color the edge and a 10X loupe to determine when I had removed all of the marker.

My questions:

1) How do you tell when you have raised a burr? I tried running my thumbpad down the knife (from spine to edge), but that did not seem conclusive.

2) When using DMT hones, how much pressure should be applied? I heeded the caution to use light pressure, and did not use much more than the weight of the blade itself. Is that too little?

3) Do you use water with your DMT hones? If so, do you wet the hone itself, or do you just wet the blade periodically?

Thanks for your assistance,

Matthew

 

[ErikD]

Just dragging your thumb from the spine to the edge you should be able to feel the burr once it starts to form. If that doesn't work for you, or you are unsure of it, you could also try using t nail. Dragging a nail from spine to edge, the nail will get caught on the sligtest of burrs once it has been formed. Then to make sure that the burr runs the length of the blade simply try running your nail the length of the blade. If the burr is complete you should be able to run from the tang end to the tip of the blade without your nail slipping off.

As far as I know you use the diamond stones dry, that is how I use mine and get good results. You don't need to use much pressure at all, in fact to much pressure could end up ripping the diamonds out of the stone.

 

[Starfish]

Just dragging your thumb from the spine to the edge you should be able to feel the burr once it starts to form. If that doesn't work for you, or you are unsure of it, you could also try using t nail. Dragging a nail from spine to edge, the nail will get caught on the sligtest of burrs once it has been formed. Then to make sure that the burr runs the length of the blade simply try running your nail the length of the blade. If the burr is complete you should be able to run from the tang end to the tip of the blade without your nail slipping off.

Thanks for the reply. I don't mean to be anal, but I want to be sure I understand the thumbnail technique correctly. When you drag the thumbnail from spine to edge, I assume that you would place your thumb such that the top side of the thumbnail is facing the blade, right?

Thanks again,

Matthew

 

[Nosmo]

-



My questions:

1) How do you tell when you have raised a burr? I tried running my thumbpad down the knife (from spine to edge), but that did not seem conclusive.



Matthew

Well you are on the right track with the felt tip.
When you have removed all the felt tip mark from one edge, it tells you that for the moment there is no need to continue that side.

So flip sides and repeat with the marker.

Now when you get to the point that the marker ink is wiped off, on both sides, with just a couple of swipes, this usually means that a burr has formed.

Below is a picture of the burr. It is the tiny white line that has caught the light in the pic.

Turn the blade over and you will not see it .

Remember the burr ALWAYS forms on the opposite side of the blade , to the side being sharpened.

When you can 'flop' the burr from side to side with easy ( couple of strokes ) you are at the stage when you can now stop sharpening and remove the burr.

 

[Starfish]

Nosmo,

Thanks for the visual images. Could you tell me what sort of light source you used to illuminate the edge, and the magnification?

When you have removed all the felt tip mark from one edge, it tells you that for the moment there is no need to continue that side.

So flip sides and repeat with the marker.

Now when you get to the point that the marker ink is wiped off, on both sides, with just a couple of swipes, this usually means that a burr has formed.

That is helpful advice - I was sharpening until I removed the marker, and then continuing on the same side. I realize now that I will likely end up with an asymmetrical edge bevel with that technique...

Thanks again,

Matthew

 

[Nosmo]

Nosmo,
Thanks for the visual images. Could you tell me what sort of light source you used to illuminate the edge, and the magnification?

Matthew

Nikon 990 set to macro on table top tripod in small homemade light tent with "Burr" illuminated with an LED flashlight, hand held, and waved about until the right effect was seen in viewfinder.

 

[Starfish]

Nikon 990 set to macro on table top tripod in small homemade light tent with "Burr" illuminated with an LED flashlight, hand held, and waved about until the right effect was seen in viewfinder.

Wow, that sounds simple! Who needs the thumbnail test?

Thanks for the pictures,

Matthew

 

[redhawk44p]

I drag the edge down the side of an aluminum can. You can feel the burr grab the aluminum.

 

[Starfish]

I drag the edge down the side of an aluminum can. You can feel the burr grab the aluminum.

redhawk44p -

I kind of thought there might be a test like that I could use. I considered perhaps wrapping fabric around a pencil and dragging that down the edge, but realized that a coarse edge would grab at the fabric as well.

I tried your test, but it was still inconclusive. Whether it's inconclusive due to lack of burr, or operator error, is still to be determined.



Matthew

 

[redhawk44p]

If you drag both sides of the blade down the can using a light touch you can feel the difference if there is a burr. Use about the same angle you would use when stropping.

 

[HoB]

you can use a little bit more than the weight of the blade. Mostly the DMT stone cuts by itself, but you can use some weight till you feel the stone cut evenly. I use a little bit of water on mine. Makes it a little bit smoother and pulls away the steel dust. Its not really needed to prevent glazing on Diamond stone so it is more a matter of preference.

Take a cheap knife and REALLY raise a burr. It should be quite easily noticable. After you felt one once you know what to look out for.

 

[VampyreWolf]

usually you can just see it with any light, I go by feel about 90% of the time.
just takes time and experience to know what to look for.

I agree with the advice to buy a cheap $5 knife and sharpen the hell out of it... make the burr really obvious, and keep going back and forth till you kill the burr.

that $5 knife should outcut most knives you'll find, if only for 1-2 cuts.

I sharpen my users about once a week, usually just the strop and fine ceramic for about a dozen strokes.

 

[Starfish]

HoB and VampyreWolf -

Thanks for the advice on using a $5 knife. I have a few "dollar store specials" in the kitchen, so I'll give that a try.

Matthew

 

[yuzuha]

Kind of depends on the steel too. My BG-42 SOG gets a fairly large floppy burr that even flakes off chunks onto my polish stone (and often as not, embed themselves in a finger so I have an excuse to use my tweezers as well as my loupe). My carbon steel wood knife gets a small ragged burr that you can feel catch your thumb nail a little when you scratch the bevel, as if trying to scratch off a spot on the blade. And my BM-910 HHS has an M2 tool-steel blade that barely gets a burr at all (I quit looking for one and just check to make sure the scratch patterns on the bevel are the same clear to the edge and still manage to get it razor sharp). D2, 440c etc will all probably be a bit different, but I've noticed that a lot of the stainless steels seem gummier (if one can use that term on steel) and make larger, floppier burrs that are more difficult to remove (tends to flop back and forth while stropping or polishing, but it just tends to flake right off on carbon steel).

You can use a little pressure on your DMT, but too much and you'll just start ripping out the diamonds (and when lapping with diamond spray or paste, your lap should be softer than the tool you are lapping, so the diamonds embed themselves in the lap and not the tool. Soft cast iron is recommended for coarser grits but, according to a diamond dust supplier, tin or copper are recommended for lapping with sub-micron grits to get the best finish on steel. Your ez-lap and dmt stones will work better on hard steel or ceramics than they will on soft gummy metals like talonite because of this effect... they are embeded in sort of a soft nickel-iron plate but diamonds are slippery and can still be ripped out if you use too much pressure). I sometimes use my DMT stones dry, sometimes with water, but mostly with a diamond lubricant/extender (seems to work best for making them cut faster and give a finer finish)

Here's a place that sells lapidary supplies and gem polishing equipment that can also be used on metal, including diamond dust, paste, lubricant, and various polishes like Linde A and chrome oxide that can be used on strops
http://www.gravescompany.com/polishin.htm

Here's a place that sells some nice leather strop plates, liquid chrome oxide and boron nitride (you could also mix diamond dust and saddle soap and rub into a leather strop) http://www.handamerican.com/products.html

 

[HoB]

I should point out that when I sharpen something seriously (meaning not for practice, but because I want the sharpest knife possible), I like to raise as small a burr as possible before I change sides. Not to protect the blade but because large burrs are sometimes difficult to cut off instead of bending them over and eventually breaking them off.

When you come to your final stage on your finest grit, I found it important to change sides after every or every second stroke going back and forth just like Vampirewolf said, to really kill that burr. You can even try to increase the angle for those final strokes a bit or try to pull the burr of with one or two pulling strokes at a slightly higher angle (again light pressure but a bit more than just the weight of the blade).

If you you are on 3000+ grid and your edge isn't shaving sharp, it usually means that you have some tiny burr left, which you can often neither see nor feel (well with lots of experience you actually can sometimes), that is bent over. Diligently going back and forth in frequent intervals with very light pressure or stropping will easily take care of that. It is really experience that tells you which way works best for you.

 

[VampyreWolf]

depending on how bad the edge is to start with, I have 200-800 grit benchstones, medium & fine ceramics, 0.5 micron compound on the strop, and 80-1500 sandpaper..

On my users, I just use the ceramics and strop. always alternating left & right, use about 1-2kg of pressure(doesn't take much), I start with 6 strokes on each side, work down to 2 and then slowly decrease pressure. The 2 sets of 6 is enough to raise a burr on a sharp knife.
ie: 6, 6,6,6,5,5,5,5,4,4,4,4,3,3,3,3,2,2,2,2,2,2,2,2,2,2,2,2,2.... strop(5-6 each side), back to the medium ceramic for about 5-6 strokes each side with light pressure.

Given the time and patience, you'd be surprised the edges you can get.
I can shave off the 800grit AO, and the 500 will just about shave.

16yrs of freehand experience has taught me what my grits looks & feels like on the edge. I sharpen by sound, but thats taken a long time to reach... my folks used to collect knives and scissors once a month at work for me to sharpen(easy money if you have the patience, and good practice).

 

[lasersailor184]

You can easily feel the bur from side to side if you can't see it.

I just use a standard lamp and flip the knife around I can see it reflecting the light on the bur. But then again, I have perfect eyesight and it might be a little hard for some of you "Older people."

The other thing I can do is I can feel it. I run my finger along side to side (not along the blade length) and I can feel which side the bur is on. The bur is only metal that has curved onto one side. One side you won't feel the bur, the other you'll feel a little lip.

 

[dennis75]

these are my methods of general edge- and burr-inspection:

- use fingertips to feel it when fairly obvious
- use back of nails to feel and display it when it's hard to tell where and on which side (not only will you feel your nail getting scratched, but the leftovers of your nail-material are right on the burr and nicks, on THAT side
- examine edge under a bright lamp at various angles for precision inspection

i found by using these methods i always get a perfectly aligned sharp edge without a burr. can't miss.

 

[Starfish]

Thanks for all of the advice. I'm going to try these out tonight or tomorrow when I get a chance. Some comments I do have now though:

I sharpen by sound, but thats taken a long time to reach

I imagine it has. For me, it would take forever since I am hearing impaired. However, it seems plausible to me that I will be able to develop the ability to sharpen by touch - i.e., the sensation of the knife contacting the stone.

- use back of nails to feel and display it when it's hard to tell where and on which side (not only will you feel your nail getting scratched, but the leftovers of your nail-material are right on the burr and nicks, on THAT side
- examine edge under a bright lamp at various angles for precision inspection

I have noticed this effect when trying the fingernail test (little bits of nail material left behind). I was not sure if that was due to the burr, or if it is because I sharpened with a coarse stone and the edge was rough.

I'll have to try looking under a bright lamp with my 10X loupe.

Thanks again,

Matthew