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SVM-45 knife jig accident

Started by Dav81, Yesterday at 09:37:23 PM

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Dav81

Hi,

I mainly use my Tormek to sharpen my planer blades, and have become somewhat proficient with the planer jig.

Got out my SVM-45, used just a few times before, to sharpen a camping knife this afternoon. Just got back from the ER with 6 stitches om my shin, and way less confidence in using my T8 for knife sharpening.

Just wanted to share what happened, as a warning to others and to and hear if anyone has suggestions on how to work (more) safely.

I was using the silicon blackstone, as I was grinding HSS planer blades before. Switched to the knife jig and worked for a few minutes, setting angles and getting a feel of the edge. I was almost done, and had set the stone to fine grit to give it a quick polish, when I guess the leading edge of the knife suddenly caught on the stone, yanking the knife and jig right out of my hands, sending the whole thing under the support bar towards me. It totally caught me off guard with how fast it happened. I jumped back to get out of the way - but too late, it got me good right on the shinbone. Which was probably a good thing as the shallow bone stopped the now razor sharp blade with heavy jig attached from going deeper, but it left a solid gash. Luckily no serious harm done and I'll be fine in a week or two with just a nice scar to remind me to respect the tool.

How many of you have had something like this happen? Are there any good instructional on how to use this jig in a safe manner? Could part of the reason be the silicon blackstone is more aggressive, making it more prone to catch the edge like this?

Any feedback would be appreciated!

RickKrung

#1
Never from grabbing, but from inattention and/or stupidity...

Tormek Bloopers anyone??? July 19, 2018, 05:09:17 PM

Rick
Quality is like buying oats.  If you want nice, clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.

cbwx34

Quote from: Dav81 on Yesterday at 09:37:23 PM...
I was using the silicon blackstone, as I was grinding HSS planer blades before. Switched to the knife jig and worked for a few minutes, setting angles and getting a feel of the edge. I was almost done, and had set the stone to fine grit to give it a quick polish, when I guess the leading edge of the knife suddenly caught on the stone, yanking the knife and jig right out of my hands, sending the whole thing under the support bar towards me.
...
...
Could part of the reason be the silicon blackstone is more aggressive, making it more prone to catch the edge like this?
...

I don't think it's more aggressive since you had graded it to fine.  One thought is that it caught on the the edge of the wheel.  You might consider adding a slight radius to the edge, as seen here...

https://www.youtube.com/live/aw4vJSUPXmk?si=LR4SDf3uJfs7ZYCf&t=483
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Herman Trivilino

I've had that happen a number of times. Fortunately, I never got hurt. My suggestion would be to wear a long leather apron and good shoes, but I doubt anyone (myself included) would be inclined to take that advice. Unfortunately, it takes a severe accident for people to become safety-minded.

Reminds me of my first teaching position. A year or two before my arrival a student was permanently blinded in the chemistry lab. She wasn't even a student in the class, but had just stopped by to wait for her friend, who was enrolled in the class and was just finishing up her lab activities when the accident happened. After that everyone was careful and safety-minded, and I carried that with me throughout my career at two other colleges.

Strangely enough, another professor at that same college had recently lost an eye while playing tennis.

I really do need to be more diligent about wearing my safety glasses when I'm in the shop or working around the house, or playing pickleball.
Origin: Big Bang

Dav81

Rick,

Thanks for the link, good thing we can learn from other people's mistakes so we don't have to make them all ourselves.  :)

I may of course have been inattentive for a split second, and I have also been stupid on several occasions before, so those factors might well have contributed in this case. However I also would like to understand which other factors to consider, so I can reduce the risk of this happening the next time around - as I like my fingers even more than I like sharp tools.  ;D

Found some threads on reverse sharpening / edge trailing, also some videos by Steve Bottorff, and that looks like a more "foolproof" way of working, as it removes the risk of grabbing. I am tempted to try that next time for knives and see how it works out.

That would be kind of chickening out instead of learning though. I am torn.

Some factors I have found from reading the forum post-accident;

  • Edge angle. Steep angled blades are more likely to grab, some mention this happening from 30 degrees and up.
  • Type of stone. Mostly referring to the japanese waterstone, which is softer than the rest, so easier to dig into with an edge.
  • Grindstone geometry. Rounding or beveling the edges with the grader, and making sure the stone is true and round is a good idea.

Feel free to add your own, anyone!

Cheers,
David


Quote from: RickKrung on Yesterday at 09:54:40 PMNever from grabbing, but from inattention and/or stupidity...

Tormek Bloopers anyone??? July 19, 2018, 05:09:17 PM

Rick

Dav81

Quote from: cbwx34 on Yesterday at 11:25:28 PMI don't think it's more aggressive since you had graded it to fine.  One thought is that it caught on the the edge of the wheel.  You might consider adding a slight radius to the edge, as seen here...

https://www.youtube.com/live/aw4vJSUPXmk?si=LR4SDf3uJfs7ZYCf&t=483


Thank you, rounding the wheel edges makes a lot of sense, good tip!

Also agree that my theory on the SB being aggressive is probably just BS  ;D  - it was likely something else.

Dav81

Quote from: Herman Trivilino on Today at 03:39:08 AMI've had that happen a number of times. Fortunately, I never got hurt. My suggestion would be to wear a long leather apron and good shoes, but I doubt anyone (myself included) would be inclined to take that advice. Unfortunately, it takes a severe accident for people to become safety-minded.


I, being an idiot, was working barefoot and wearing shorts, just enjoying a lazy Sunday ;D  ::)

Have actually ordered a leather apron though, I think they look a bit badass, so I might actually use it.