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The Newbies Arena Are you new to knife making? Here is all the help you will need.

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  #1  
Old 09-05-2012, 01:25 PM
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rockhound rockhound is offline
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DIY Jig - Hollow Grind w/Angle Grinder

So....
I'm going to ask your opinions on this.
I am a hobby knifemaker, not a production guy.
I am not at all interested in spendy equipment ($500-$2k++... belt grinders, etc) but would like to create a hollow grind bevel on some of my knives.
I'm confident with my skills thus far draw-filing to create flat bevels. I enjoy draw-filing but this will not effectively create a hollow grind bevel as far as I know... and frankly wouldn't be worth my time.
Considering the tools and materials which I already own.... I stumbled upon a nifty little DIY "Knife Bevel Grinding Jig" tutorial. I can whip this up in a day I reckon and start working on my first hollow grind, for virtually no cost.
Any thoughts? http://myhome.mweb.co.za/~20022586/jig.htm
Thanks.


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Old 09-05-2012, 08:00 PM
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Ray Rogers Ray Rogers is offline
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I didn't look at it but if you don't want to build or buy a grinder then an angle grinder would be one way - maybe the only way - to get a hollow grind. You could build a jig or learn to do it freehand, whatever works. I'd keep my eyes open for a grinder though, even if it is just a urethane coated cart wheel (cheap) on a shaft with a cheap motor to spin it. Not much expense there and much nicer to use...


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Old 09-05-2012, 08:48 PM
Jay-Z Jay-Z is offline
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I am in the same boat your in Rockhound, trying to make a few knives as a hobby on a shoe string budget. I think that jig is a great Idea. My only thought on it is would the rod holding the grinder be strong enough to "control" the grinder, mine has a ton of torque.
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Old 09-05-2012, 09:52 PM
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If you already have the supplies around the shop, give it a try. I don't think that I would sink much money in it though.
IMO this should "rough-in" your bevel.
Jay-Z, I think that a 7" Milwaukee or the like would have WAY too much torque for this but a cheap little 4 1/2" might be manageable.

Brett
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Old 09-05-2012, 11:18 PM
Doug Lester Doug Lester is offline
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If I didn't want to purchase a belt grinder, I would look a bench top grinder with stone wheels then finish the grind off with sand paper or oil polishing stones like the ones machinists or dye makers use. That or I'd stick with doing flat grinds with files.

Doug


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Old 09-06-2012, 06:05 AM
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Interesting jig. Even the 4 1/2" inchers have a lot of potentially destructive torque. It will require a very light controlled touch. Side grinders tend to eat metal faster in the wrong places than the right ones. I can see it working ok. You can always follow the grinding disc with a layered sanding disc the same size -- as long as the rotation is in the correct direction -- this will reduce the hand finishing requirements.
I can see potential for some interesting "jump n run" if something slips just a tad or the operator gets distracted. Be diligent and careful.


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Old 09-06-2012, 10:24 AM
Doug Lester Doug Lester is offline
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Ok, I got the picture to load this time. I'm still not sure how that will work to establish a hallow grind. It looks to me like you would be running the wheel of the angle grinder into the jaws of the vice. I would also be worried about grinding a blade in it that had a distal taper because it would be impossible to clamp the blade evenly along the entire length of the jaws. I could easily see a situation where the angle grinder could catch the blade, snatch it from the jaws and throw it. Even if all it did was move the blade in the jaws you could easily ruin the blade. I'm not as optimistic as Carl about that rig and he expressed serious reservations. I think that the money that would be spent building that jib would be much better used to start a savings account to buy one of the less expensive belt grinders. If you do build it be very, very careful. I remember what Jim Hrisoulas said in one of his videos: hand tools injure, power tools maim.

Doug


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Old 09-06-2012, 10:46 AM
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Thanks for the thoughts folks, I appreciate it.
Doug, as I mentioned... I can make this for "virtually no cost", that would make for a small savings account, lol. Regarding your suggestion "buy one of the less expensive grinders"... I cannot justify that. 1. When I purchase tools or machinery, I don't like to skimp. I own a lot of mining equipment and have learned this lesson. 2. Even the "less expensive" grinders (with motor Kalamazoo example) is over $500 + belts and accesories. That's not practical for my kinfemaking hobby budget at this time. If I was in this to make money... fine, but I'm not.
I do own a quality stone-wheel bench grinder and have considered that briefly but ruled it out as being potentially too abrasive. It can also throw objects with wicked velocity in the blink of an eye. It scares me more than my angle grinder in that regard.
I think that I'll try to hollow grind with my 4" angle grinder - freehand, without the jig. I have many years of experience using it in unusual applications and a steady hand. I also have a good amount of leaf spring steel laying around to practice profiles and bevels before applying the technique to the good stuff.
Points well taken regarding the dangers involved with using a high rpm angle grinder and I will take necessary precautions.
Jay... we'll get this figured out yet!


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Last edited by rockhound; 09-06-2012 at 10:50 AM.
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  #9  
Old 09-06-2012, 08:35 PM
Kostoglotov Kostoglotov is offline
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In lieu of the double nut, look at Northern Tool/Harbor freight for a universal joint with a threaded end.

The set up works but its pretty limited

Honestly, Instead of building something like this, I'd put the effort into building a 2X72 Grinder, depending on how much you can scavenge, they can be relatively inexpensive
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Old 09-07-2012, 06:48 AM
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Thanks Kosto,
I've decided not to build a jig but I know exactly what you're talking about with the u-joint setup. I saw something similar someone had built as a detail-filing jig utilizing that.
I may try to fabricate a 2 X 72 at some point, good advice.


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