View Full Version : Does Durometer Affect the Plunge?


TWITHERS
05-03-2013, 01:35 PM
Hello I am new here. I have been reading for awhile but this is my first post. I have the SR Johnson video and it has helped me a great deal. So has this forum. Thank you. I have a Grizzly grinder and made some knives that were decent. To me anyway. I was happy with the radius at the top of the grind at the plunge cut. I now bought a B3 and cannot get that radius to save my life. Of course occationally a belt is broke in just perfect and I can do it but I do not have control over it nor can I repeat good results. One of Mr. Johnson's post stated a 90 Duro wheel helps make the radius. If I understood it correctly. I bought 70 Duro serrated and 60 duro smooth wheels in all sizes so I hope I did not make a mistake. The Grizzly wheel is alot harder than the new wheels I have. Any help would be appreciated.

Steve
05-06-2013, 05:35 PM
Some slightly (SLIGHTLY!) round off the corner of their serrated wheel to get nice radius. (Careful, though, you can't undo it without grinding down the face and diameter of the wheel!) I no longer do so. It can be influenced by how much belt hangs over the edge of the wheel, also. You can get to the point where you can pretty much "carve" that radius, but, still, some luck and just karma seems to come into play a lot of the time. Keep practicing, trying different things. I doubt the difference between 70 and 90 Duro. would make a diff. If anything, the softer wheel would tend to make a nicer radius. Wish I could say, "Do this, or that" and all would be well, but I am sorry that I can't. Keep practicing......Let us know how it goes, if you would, please.

TWITHERS
05-07-2013, 07:54 AM
Thank you for your reply. I am glad to hear the problem is me not the wheels. I can practise. I can't change the wheel without spending more money.

TWITHERS
05-07-2013, 09:09 AM
If you would, please explain the "carve" or "sculpt" the radius in the plunge. I know it must be a very difficult thing to explain. Maybe it is "feel" and you can't explain that. Is there a direct correlation between the upper radius and the curve at the blades edge where it meets the ricasso? I apoligize if you gave me all the information you could already. I am thinking when I am getting close to the ricasso you mean to start bringing the blades towards me a little, still keeping in contact with the wheel and still moving towards the plunge. Strange how a belt that is broken in just right makes it so easy. Just run the plunge right up to the edge of the belt and it is done. I might be on the wrong path but I am trying to figure out how to break the belt in just so.

Steve
05-07-2013, 09:51 AM
Feel free to take a scrap piece of steel and, with the belt running, press against the belt on the edge fo the wheel and break it in a little bit. Not too much, it will become mushy. Play with it a bit, old belts, new belts, use the edge of the belt to cut away exactly what you want, both at the bottom and top of the blade. It takes, again, practice, time and experience and, most of all, concentration on what the belt is doing and where it is doing it. Sorry, as you mention, it's hard to explain, but it sounds like you have the ability and skill level to work it out. No short cuts, IMO. Go for it, you can do it, Im sure.

TWITHERS
05-07-2013, 01:35 PM
Thank you very much for the advice and kind words. I think it is so great how a man as accomplished as you would take the time to give advise to new makers that you don't know and may never know. Thank you. I'll come up with another question soon enough.

TWITHERS
06-14-2013, 03:04 PM
Hey Steve I have an update on my grinding. I have found that the belt tension being tighter helps. I was frustrated and decided to go back to using the Grizzly and as soon as I put a belt on it I noticed how tight the belt was. On the grizzly the tighter the belt the better the tracking. On the Bader of course the belt does not need to be as tight to track well so I did not have it as tight. Believe it or not as soon as I made the belt tension tighter it made a difference. Does this make any sense to you? I figure the added tension just helps the belt roll a little when tracked over the edge.

Steve
06-15-2013, 12:30 AM
Sounds exactly right. Put the belt on and use very little tension and it will scoot all over the wheel. That is very good advice and it will help many new - and old - makers, I'm sure. Thank you!

Steve M
06-15-2013, 06:10 PM
" I am thinking when I am getting close to the ricasso you mean to start bringing the blades towards me a little, still keeping in contact with the wheel and still moving towards the plunge."

Being new at this I have also spent quite a bit of time trying to figure this out so as to get consistent results regardless of the belt type or if it is fresh vs broken in. I've been experimenting with large sweeping plunges and the penny dropped when i thought about it like this:

Imagine a potato peeler mounted in a vice, blade up and facing you, now grab a block of cheese and take slices across peeler to resemble a knife grind with a sweeping plunge without tilting it in any direction and take note of your hand movements in the plunge area, it's just like you described above.

What's amazing is that it works with a fresh 50 grit ceramic belt without tracking it over the edge of the wheel any more than normal for roughing out, however as you go up the grits and into the cork it helps to track over gradually more and more to about 1/4" to prevent the corner of the wheel gouging the "ramp" up the plunge to the ricasso.

Hope that was helpful, The concept has added some flexibility and consistency to my grinding.

Cheers,
Steve

TWITHERS
06-25-2013, 05:49 PM
Thank you. That is helpful. I am a stubborn one though. My first question was "does durometer affect the plunge?" Mr Johnson said probably not,. Pop from Pops Knife Supply said the same thing. But I have to give it a shot or I will always wonder. I mean no disrespect to the people who have given me advice. It is obvious they know what they are talking about. I just ordered a 90 duro wheel and an 80 duro wheel. I'll keep you posted so everyone can laugh with me when I find out I wasted good money going against good advice.

TWITHERS
07-23-2013, 08:23 AM
Well another update. Like I said in my last post on this thread I ordered one 5" 90 duro wheel for my Bader. I honestly could tell the difference imediately but that is not to say the radius at the top of the plunge was just the way I wanted, it wasn't. The difference was though that I could make a connection between my hand movements and what was occuring to the grind. By the time I had finished rough grinding that first knife I started looking at it like this. I would rough grind all the way to the center line (just shy of prior to heat treat) just as before. Before making it to the top make sure the grind line at the plunge was high enough. I had a tendancy to trail off as I got to the plunge for fear off grinding too much, I would not grind enough. If it was too rounded then I would have a lot of material to take out and in doing so I would mess something else up. If I left the radius too sharp then all I need to do is move the grind back slightly to get a nice radius. It is just as you said "CARVE" the radius. I do not mean to imply that all of a sudden I am an expert, not at all. But I tell you what it is a great feeling when you know that your hand movement are making that radius and it is not just luck with a perfectly broken in belt. Now the issue of the harder durometer. It has helped me but why? When I was using the Grizzly I think I was somewhat carving my radius, I just did not know I was doing it and being new to knife making the movements are not second nature yet. The softer wheels through me off and I was learning how to grind all over again. 90 duro is what I learned on and what works best for me. A gentleman I spoke to over a Bader said 70 Duro should be just fine, that is what most knifemakers use, you must push really hard. I believe he must be a least partially right, it makes sense. If I do push hard, the softer wheels would distort and I would get no consistency. I did not know that I pushed hard. I do know I use belts longer that I should. They cost so much AND a dull belt is more forgiving. So maybe using dull belts make me push hard. I love knifemaking, everything you do is connected with the next thing, or the previous thing you do. I wish I would have found it sooner. I apoligize if this post is just too long. Thanks.

Steve
08-02-2013, 02:58 PM
I think that all of the above is correct. I still think that a 70 vs 90 Duro. wheel wouldn't make a lot of difference, unless, as you say, you are pushing pretty hard, but sharpness of the belt, wheel speed, type of steel could all enter into the equation. A 90 Duro. wheel is really hard, though! You can push hard on a softer wheel and have certain things happen. Remember: everyone will do it differently, pressure, belt grit, belt size, width, etc., belt condition..... The hard wheel works, always has, so something has to be said for tradition and experience, I guess and you seem to agree, so that says something. I just hope all is going well and that things will keep working for you. We'll be glad to help, if we can in the future. Good luck and thanks for all your work and reports. Knifemaking is a continuous learning process, never ending, if you want to keep striving for perfection. Everyone has an opinion and their way of doing things, all might be right, or work well, but we all know that we don't know everything and if we are willing to learn and listen, things/life can be easier and more enjoyable. Thanks!