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The S.R. "Steve" Johnson Forum Specialized knife making tips, technique and training for "ultra precision" design work enthusiasts. |
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#1
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Setting up hollowgrind plunge cuts.
On my flat grinds, I often use a filing jig to accurately place the plunge cuts. On my hollowgrinds, which I have just started doing, I have had good luck so far getting things nice and even with just using a fresh belt and then giving it a nice radius with tracked-off J-flex belts.
There are just some days NOTHING wants to line up, that blade just gets longer and longer as I try to cut fresh matching plunge cuts on both sides... Is there any role for a filing jig with hollowgrinds ? Am I missing something ? Thanks in advance. Jason. __________________ JASON CUTTER BLADEART Jason Cutter @ Dr Kwong Yeang Knifemaker, Australia (Matthew 10.16) |
#2
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Jason,
I don't even try for good plunge cuts. More accuratly, I mark my blade 1/8" from where I want my plunge cuts to be. I grind my blade from that point on, not worrying about the plunge cuts. when the blade is ground and looking right, I just push the grind back to the point I REALLY want the plunge cuts. I do this on both sides and they come out right every time. Some people try to cut right where they want the plunge cut to be but that never works for me so I sneek up on them and catch them off guard. Edited to add: Some people will clamp some steel across the sides of the blade that will stop them from going further when the steel hits the side of the wheel. This makes the plunge cuts equal on both sides. |
#3
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Ditto here. However, you'll reach a point where you can start where you want to be and stay there.............................in about 20 years!!
Just leave some room and finish it up when the blade is ground, or even wait until after heat treat, for the final tru-up, when there's more resistance and mistakes happen a bit more slowly. |
#4
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Thanks.
I am also very thankful for J-flex belts and variable speed. Jason. __________________ JASON CUTTER BLADEART Jason Cutter @ Dr Kwong Yeang Knifemaker, Australia (Matthew 10.16) |
#5
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Bob is right, sneek up on it. Gib
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#6
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I start at the edge and work upward......then do the other side to match.........when I first started it was a real challenge....now its one of the easiest parts of making a folder.
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#7
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Samo here (cut the plunges at the end).
On thing tho is I use the rest. Get the blade edge up there and roll it into position. If the blade is aligned properly you'll see the gap (blade edge to belt) nice and even. As you roll keep the gap even. Once the cut is done and the new cut matches the old, it will tell you - the roll will stop. Now move left and right to smooth it out. Personally I have to do it with the rest on, reading glasses and my face right in there. Steve |
#8
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Like Steve says, in about twenty years. I say in about twenty years you will start having better luck. Some days it seems like you had never sat in front of that machine before. Just slow it down and be very carefull.
Steady your elbows and arms close to you waist, and maybe on top of your legs. Ricardo Velarde www.velardeknives.com __________________ Ricardo Velarde 7240 N. Greenfield Dr. Park City, Utah. 84098, U.S.A. (1) 435-901-1773 www.velardeknives.com |
#9
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Always do your "offhand" side first. Even up with your good side.
Truthfully, I just hold em in steady and at a high angle then run them up and out for the rest of the blade. I don't get to carried away with it though. I clean them up after heat-treat with j-flex so it's harder to screw up. (not that I still don't. ) __________________ Michael Burch Full-time Knife Maker michael@burchtreeblades.com www.burchtreeblades.com |
#10
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Quote:
-Frank J Warner __________________ --Frank J Warner Happiness is tight gibs and a flat platen. http://www.franksknives.com/ |
#11
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Frank:
I started off just as you sugested and did the offhand side first and got so good at it screwed up my good side. James __________________ Blademan KnifeMakers Are Pretty Sharp People |
#12
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Lmao James, I think that's what happened to me!!
What drives me nuts is I can get the plunge grinds even but virtually never get them to look the same, the same profile or contour. You know what I mean, one will have a nice dished out flow to it and the other one will have a sharper curve in it. Drives me up the wall! Most people would never notice it but I do. I just don't understand why you can't get the same grind on both sides of a blade when the edges of the wheel are shaped the same. Michael |
#13
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I had the same problem and every once in a while it still pops up and seriously peeves me. I find that it's just my eyes playing tricks on me. It may look like the blade is set at to make the "flowing grind" but I'll go against my eyeball's judgement and hold the back end a little higher to get it right. That probably made no sense.
__________________ Michael Burch Full-time Knife Maker michael@burchtreeblades.com www.burchtreeblades.com |
#14
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Ed Fowler gets the nod for this one. Occasionally, one side will cut different than the other side. Flip the belt over and try that. I've had to do it a few times and it makes a difference on some belts.
I give myself an 1/8" or so and when I get to 220 grit, I slow the grinder way down, something like 100 or even 50 rpms and using a Jflex overlapped push against the side of the wheel until they are even. I used to use 120 for this but I find 220 a little slower and more consistent. Once in a while they come out dead even and I just giggle when that happens. If I'm having a tough time getting the top corner of the plunge cut to be a smooth radius, I'll move the belt by hand with a 120 grit. |
#15
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I do it the same way...rough grind with 60 grit and try to get them fairly even and then with 120 grit I get them to match....220 gets the final touch before heattreat.....after heattreat i take them to 400 and 600.....the last two if carefull wont remove much but still keep them matching...
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