MEMBER ITEMS FOR SALE
Custom Knives | Other Knives | General Items
-------------------------------------------
New Posts | New PhotosAll Photos



Go Back   The Knife Network Forums : Knife Making Discussions > Custom Knife Discussion Boards > Knife Making Discussions > The Newbies Arena

The Newbies Arena New to Knife Making? Here's all the help you need ...

Reply
 
Thread Tools Display Modes
  #1  
Old 10-07-2017, 06:32 AM
dtec1 dtec1 is offline
Guru
 
Join Date: Aug 2015
Location: putnam county NY ....about 45 mins north of new york city
Posts: 1,367
large knife sharpening

Hey guys so this is probilly something I should have learned very well by now. Anyway I am making a large competition style knife. So the idea is a full flat grind with a convex edge. I am making this blade out of cpm s35vn. I know a lot of these type of knives are carbon but I wanted to make this from stainless. Now almost everything I read says covex edge is the way to go to keep the edge from getting chippy. I think that goes even more so with a stainless blade as they are generally harder. So in the past I always did a flat edge I would put the secondary bevel in on the grinder and go to my edge pro. So the edge pro gets to be a pain with large knife and also it cant do a convex edge. So what I have tried is to sharpen on the grinder on the slack right behind the idle wheel on the top of the platen. I have tried a few things first with a 220 belt then go to the buffer and knock off the bar. i have also tried to knock off the burr with a leather belt with honing compound and green chrome on it. I also tried to knock off the burr with a ceramic honing rod. The best i have done was starting at 220 grit and going all the way to 800 grit then to the ceramic honing rod....it doesn't get as sharp as i want it it has trouble slicing through thin paper it does get through kinda but not going clean through like it should.....i would really love to hear everyones method for doing a convex edge or ANY advice on the topic...
Reply With Quote
  #2  
Old 10-07-2017, 03:59 PM
epicfail48 epicfail48 is offline
Enthusiast
 
Join Date: Aug 2017
Location: Springfield Mo
Posts: 60
Can't say I do convex edges all too often, but the ones I do I don't use a machine. Wet/dry sandpaper on a soft backing, either leather or something like a mousepad. Little bit of pressure and the leather/mousepad squishes enough to get a decent convex edge, keep going up through the grits until I've got it where I want it
Reply With Quote
  #3  
Old 10-08-2017, 03:29 AM
jimmontg jimmontg is offline
Guru
 
Join Date: Jan 2016
Location: Now live in Las Cruces NM.
Posts: 1,016
Dave I don't make a convex edge, I do make some knives with a convex grind. Whether it's stainless or not a regular flat grind edge shouldn't be chippy if the HT is good. Those S35VN knives you sent me were not chippy and I put a flat grind edge on them. As I sharpen by hand the edge may get a little convex, but it is so short of a distance it would be hard to notice. A convex grind is good for wood carvers, axes and larger knives and I mean a convex grind with a straight grind edge. I have made a few knives with a convex grind and I found out that a convex grind is good for a filet knife too as long as it isn't too thick, which most filet knives aren't. If you hone the edge with a leather belt and rouge on it it will make the edge a little convex, but if you want a convex edge use an 600 grit belt and then hit it lightly with a fine stone. Run the stone into the edge, not away and you will not create a burr. Believe it or not, but a finely honed knife isn't good for most cutting chores as it doesn't have micro teeth. And a convex edge wouldn't slice through paper very well either I would think.
Reply With Quote
  #4  
Old 10-09-2017, 02:40 AM
Bob Hatfield Bob Hatfield is offline
Enthusiast
 
Join Date: Apr 2004
Location: Northern CA.
Posts: 99
I have to disagree about a convex edge will not slice though paper very well. I use a convex grind on the cutting edge of all my hunting knives. I have a 2X48 horizontal grinder. After heat treat and finish hollow grinding, I use a 100 grit belt to get the edge to a burr. then 220, 400, 800, 1600 grit then polish with a 2X48 leather belt loaded with green chrome.
I can lay my knife edge on the edge of a notepad paper and just the weight of the knife will cut though the paper. My S30V knives are heat treated to 60RC


__________________
RELH
Reply With Quote
  #5  
Old 10-09-2017, 05:10 AM
dtec1 dtec1 is offline
Guru
 
Join Date: Aug 2015
Location: putnam county NY ....about 45 mins north of new york city
Posts: 1,367
Thanks guys...
Epicfail---Yes I have seen the sandpaper and mouse pad thing....I am sure it works and would be a great way to re sharpen the knife if your out and about...if I really cant get it sharp doing it mostly on the grinder I may try it but there are a lot of guys out there that use a grinder and sharpen there knives in the matter of 3 minutes so I am hoping its just a thing of practice maybe....

Jim...Yeh I know that blade I sent you was good but it was a smaller blade not ment to take as much abuse as this one. Have you ever seen the blade sport championships? this knife will be tested with similar stuff that they do. I want to see how far performance wise I can take a knife so I figure similar tests to the world championships will be a good start.....ALMost everything I read says all those knives have a convex edge I think it helps not to get chippy and I think more material behind the edge might also help keep it sharp. IF with a lil more playing I cant get it as sharp as I want well then I will flat sharpen it and see how it goes. Jim may I ask that knife I sent you that you said the HT was really good what tasks/tests did you put it through?

Bob....thank you I know a convex edge will slice through paper with no problem I have seen it done before....it just wasn't me that sharpened it. maybe I will add that extra last step and go higher than 800 grit and see how that works it might make a difference.
Reply With Quote
  #6  
Old 10-09-2017, 03:18 PM
epicfail48 epicfail48 is offline
Enthusiast
 
Join Date: Aug 2017
Location: Springfield Mo
Posts: 60
Quote:
Originally Posted by dtec1 View Post
Thanks guys...
Epicfail---Yes I have seen the sandpaper and mouse pad thing....I am sure it works and would be a great way to re sharpen the knife if your out and about...if I really cant get it sharp doing it mostly on the grinder I may try it but there are a lot of guys out there that use a grinder and sharpen there knives in the matter of 3 minutes so I am hoping its just a thing of practice maybe....
Never judge yourself by another mans yardstick. There's a few guys out there who do all their sharpening exclusively with a grinder, sure, but there's also people out there who use those pull-through sharpeners too.
Reply With Quote
  #7  
Old 10-10-2017, 03:16 AM
Naboyle's Avatar
Naboyle Naboyle is offline
Steel Addict
 
Join Date: Dec 2012
Location: New Florence, Pennsylvania.
Posts: 263
I had emailed Ed C about the difference between sharpening sharpening stainless blades and carbon blades about two years ago. Here is the reply he gave me on his approach on sharpening stainless......

When it comes to stainless blades, I start at a 220, and work my way through belts to a 1200. Sometimes it works, and sometimes it doesn't. I can get a scary sharp edge on a carbon steel knife every single time, and in short order, but EVERY single stainless blade I sharpen is an exercise in patience, and I can never get the same level of a quality edge on stainless as I can carbon. My best bud (Steve Kelly) and I often talk about this very thing.... he does pretty much all stainless, and he will flat tell you that you simply don't get as sharp, or as quality of edge on stainless that carbon offers.

I wanted to emphasis..... as I said, YOU are not doing anything wrong with the sharpening/stainless..... what you're discovering is why many makers simply don't like stainless. It makes everything throughout the entire "knife" process more difficult/less efficient, then carbon steel. I've always marveled (and just shake my head) when someone demands stainless steel..... compared to most forged carbon blades, the ONLY advantage I can see is the fact that the individual/owner doesn't have to care for a stainless blade (in the rust/tarnish dept). But, the problem is that being a "lazy" knife owner is so ingrained in many that they pale at the though of actually having to care for a knife.....so in order to keep those folks happy, the stainless will always be there.

I know that doesn't give you anything that solves your issues.....but it's not something that I can give you directions for, that will work every time, or solve the pain involved sharpening stainless.....honestly, I don't say this very often, but when it comes to sharpening stainless blades, I catch myself usually just giving up and saying "that's good enough".
Reply With Quote
  #8  
Old 10-10-2017, 06:38 AM
dtec1 dtec1 is offline
Guru
 
Join Date: Aug 2015
Location: putnam county NY ....about 45 mins north of new york city
Posts: 1,367
Epicfail.....I get what your saying there are 2 makers that are somewhat close to me...one I have gotten very close with the other I have met a couple times. The one that I got close to does a lot of his sharpening on the grinder. He uses carbon steel tho for 90% of his stuff. so now I understand there is a difference however the other guy is like me uses mostly stainless and I get what your saying by not judging my self by what some one else can do but he sharpens a stainless blade to scary sharp very quickly...I wish I could do it that quick and that good.

Naboyle...Yeh I started doing it like the maker that uses carbon steel that I mentioned above. and like I said couldn't get it sharp. That is when I spoke to Ed C as well and he told me the same thing go up in grits I only went to 800 not 1200 so I will try 1200 and see how that works. But I got the closest going up in grits as you and ed had mentioned.....I do have a feeling that like so many other things practice practice practice will make a difference. dealing with stainless it might be harder but I know its possible the other maker I mentioned that uses stainless he didn't go up in grits he started at a slightly worn out 220 and then leather belt with compound. I saw him do it so I know its possible but again practice maybe? I was thinking maybe if just going to 1200 doesn't work first go to 1200 on the grinder then do the last grit slightly higher than 1200 maybe 1500 but do it by hand on a mouse pad maybe the combination will work out. thanks again guys! ill keep you guys posted
Reply With Quote
  #9  
Old 10-10-2017, 02:31 PM
jimmontg jimmontg is offline
Guru
 
Join Date: Jan 2016
Location: Now live in Las Cruces NM.
Posts: 1,016
The tests and sharpen.

Dave I chopped through a bunch of dymondwood first thing. It didn't affect the edge that I could see. Then I commenced to slice cardboard. Lots of it until the edge got dulled and it took a lot Dave. I would guess about 20 feet of cardboard if not a more. Cardboard is abrasive as it picks up dust and I was using recycled. I initially sharpened the blade with 220. After establishing the edge I wanted, I used a medium grit EZE Lap diamond sharpener that is over 15 years old so it is between medium and fine. Once all the edge was even I finished it with a hard and fine Arkansas stone. It would pop the hair off your arm.

Because of the way I sharpen I do not leave a burr on the edge. I always slice into the stone and never slide backwards, backwards leaves a burr. I sharpen by hand, always have, it is how I learned. I also hold the stone in my left hand and twirl it as I sharpen, it is why I never round off the point on a knife. Also why I never sharpen after a couple of beers. I've cut myself doing it that way, but again it is how I learned.

I really don't have a problem with carbon or stainless. It does depend on the edge geometry, but the only real hassle I've had sharpening a stainless knife is one with Chromium or Vanadium in its alloy as it really makes it tough to sharpen. Vanadium carbides like in the S35VN Dave make a knife abrasion resistant and therefore hard to sharpen. Hard 440C, I mean like at HRC 59-60 also create chromium carbides and they are harder than iron carbide and that is why a carbon steel knife tends to be easier to sharpen. I use a diamond, it is the only sharpener to use by hand as trying to sharpen good stainless knives with Arkansas, Crystolon or India stones just takes too long or even Chinese polishing stones.

I will start with a fresh, this is important, 220 silicon carbide or coated pre-lubed ceramic belt and establish the edge. A slightly worn belt and you could easily turn just barely a small part of the edge blue and then you have softened it. Remember that the stainless, if HT properly and especially if it has had a cryo in liquid nitrogen will have very tough abrasion resistant carbide and it is very easy to anneal the edge, I know from experience, I will not use anything but a new belt and I will not use cheap AO belts. The silicon carbide belts are best because I can keep them damp and therefore cool. You don't have to spray water all over, just keep it damp with a wet rag.

I have a S30V filet knife I can put a shaving edge on, though I won't as that is too sharp for filleting fish. I put a working edge or what some call a butcher's edge, about 800 grit. I suspect that a lot of stainless knives not getting sharp from sanding belts may have a lot to do with the chromium and vanadium carbide's hardness and if you throw some niobium into the mix like with S35VN it would be just a bit harder. You also have to take into account that some custom knives are HRC 61-62 hard and even some Scandi knives made from high carbon like 1.75% come in at HRC 63-64 and that is harder than most files. The finer grits do wear out fast if not coated. I have noticed this with the 15 micron belts, they must be coated and as I say below I use Tap Magic, a thin cutting fluid.

I can only tell anyone who is using belts to get a final edge to be sure and use new sharp coated belts and do not use cheap AO belts. Those 1200 grit or 15 micron belts don't last very long. I use a rag and put Tap Magic cutting oil on them to keep them clean. I put it on a rag and apply it very thinly and often. I would also strop it by hand on leather glued to a stick. If I want a razor's edge I strop on leather glued to a stick about 10" long, I do not use polishing compound I use 10,000 grit diamond paste. I use diamond paste in different grits for polishing as it works very fast.

As for a convex edge having a hard time slicing paper I am referring to a steep edge geometry not a thin convex edge. No point in putting a thin convex edge over a flat edge if the steel is chippy it will be chippy with both. I would use CPM 3V if going with a thin edge or a good carbon steel like 1080V or O1 with Vanadium, it usually has .2% and all that does is make a finer grain. O1 is my personal favorite for a carbon steel alloy. Not all O1 has the V so check.

How to tell the knife is sharp after the 220 grit grind? Look down onto the edge, edge up and if you cannot see any shiny spots on the edge the knife is ready for the next size or in my case its ready to finish by hand. Just in case there is a newbie reading this.
Reply With Quote
Reply

Tags
advice, belt, bevel, blade, buffer, carbon, ceramic, clean, cpm, edge, flat, flat grind, grind, grinder, knife, knife sharpening, knives, large knife, leather, make, making, rod, sharpening, stainless


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Knife sharpening using the Bubble Jig. Fred.Rowe The Newbies Arena 2 05-21-2010 10:04 AM
Knife sharpening discussion in TKN Zeasor Ask a Computer Geek ... General Support 3 02-11-2008 02:33 AM
Knife filing/sharpening set up B.Finnigan The Outpost 11 04-16-2006 09:38 PM
Large Knife caveman The Display Case 4 03-14-2005 10:24 PM
Knife sharpening DiamondG Knives The Outpost 7 08-26-2002 03:55 PM


All times are GMT -5. The time now is 04:13 PM.




KNIFENETWORK.COM
Copyright © 2000
? CKK Industries, Inc. ? All Rights Reserved
Powered by ...

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
The Knife Network : All Rights Reserved