- Joined
- Jun 5, 2012
- Messages
- 1,071
Hi All,
Thought I would share the repair I did for a local customer. Some member of his family (none have come forward to be shamed as of yet) decided a good way to split a bone in roast was with this knife and a mallet. It did not work out too well as you all can see below. This chronicles my evening's diversion in the shop. I had some spare time since my paypal got nuked by the home depot breach, and I couldn't prep shipments. Of course they reversed the charges and restored my balance five minutes before the post office closed today.
This is a fairly nice German made Wustof Classic. I own a couple blades from this series and they are some of my favorite working blades in the kitchen. IME at least, Wustof runs their HT a bit higher on this particular series, than many well known midrange premium production blades that I've encountered. Considering their reasonably thin geometry and higher hardness, they are impressively resistant to different types of edge damage in my experience. I'm pretty sure they run this steel up to the max which from what I understand is about 60rc. That it took this kind of abuse with only a tiny crack, is quite impressive. Solid HT.
Normally I wouldn't recommend a repair like this to a customer if the blade was less than $100 average retail. These guys run about $150, so definitely worth a $50-75 regrind, especially considering that the knife probably could have used a regrind straight out of the box, and had close to the performance of finely tuned custom, at probably half the price. No criticism towards Wustof, just a side effect of production. In his shoes I *may* have chosen to write it off and use it as an excuse for a new knife, but this route is much more wife-friendly, and he will end up with a pretty darned good blade for not much out of pocket (considering it's pretty much trashed).
This is the patient. The main damage extends about 10mm into the blade, with about 2mm of crack in the worst area. There is secondary damage from the customer's (extremely unsuccessful) attempt to straighten the blade before handing it over to me, which extends about 20mm above the edge. Luckily this was fairly light.
I put a fine point sharpie in my compass and used it to trace a line along the edge. This line is about twice the height of the crack. I'm not grinding up to it, just using it as a guideline.
Next I grind up to the top of the crack. This will prevent it from spreading as I straighten the bend. I went about halfway up from the original edge to the scribe, and make a few very minor personal preference adjustments in the profile, slightly increasing the angle of the rear portion to the handle, and slimming the tip while lengthening and smoothing the belly.
There are a few ways this could be done, but this is how I decided on this one. The tool I used is the Knipex Plier Wrench, It's basically a parallel jaw plier or crescent wrench head with plier handles. It's a super handy tool to have... they have a high lever ratio and grab HARD. You can squeeze the corner of a sheet of aluminum so hard with these things that it will extrude into foil.
They're generally meant for bolts and fittings, but also work amazingly for bending and straightening. I don't use crescent wrenches any more, ever.
I adjusted my heat gun to a low end temper temperature, and set it on the table blowing up on the edge of the blade as I worked it. After some coaxing and concentration, I got it into the condition seen below.
I also took it over to my polished mini anvil and did some light peening as needed.
These are the two sides after straightening. One side needs a bit more tlc in the regrind than the other, due to damage by owner's attempt to repair.
I start on the easy side first. There isn't an extreme amount of adjustment to do on this side, so I start out with a fine grit structured belt. They aren't good for everything, but this is one thing I find them to be quite good for. They seem to do quite well for slight geometry adjustments and scratch removal. Not all that great for actual grinding though, IME. This is after the first few light passes, just to see where things were at. Notice how there is a significant roundover in the geometry about 1/8" down the spine. This was not from my platen, It was freshly resurfaced with a large face mill immediately before the blade went to the grinder.
This is the damaged area on side one about halfway through the regrind. The flaw in the factory geometry can be seen much more clearly in this shot. I suspect this is possibly an artifact of the trimming process after forging, but I could be mistaken. More importantly, the blade geometry as a whole needs a bit of fine tuning to be where I like it, especially with having lost a good 1/8" of edge grinding past the crack.
This is after finishing the main blade geometry adjustment for the first side, and beginning to regrind the plunge. I didn't want a goofy transition between my regrind and the factory plunge, so I reground it to align perpendicular to the blade length. The factory grind was done off-angle, and there was no way to get a uniform finish up to the edge of the bolster otherwise.
First side done. Final geometry was done with Norax X45, scratch refinement was done with 400 grit cork. The cork took out the very slight hiccup in geometry that can be seen in the reflection about halfway through.
The opposite side needed a bit more love, So I walked it down from a fresh 3M 947A to Norax X45. It would have been a waste of time to jump in with the finer grit as I did on the other side. This is after some "light hogging" at the lowest grit, and I was edge grinding only. I straightened out the geometry on the next grit up.
This is side 2 finished, including cork belt, and after final sharpening at 2k grit and strop. Shaved a patch clean from my upper leg in one stroke. Just as a final note, I did all grinding with fresh belts on medium low speed. This type of grinding is quite easy on the belts, so the expense of using so many fresh belts isn't an issue, and that way I could concentrate on the edge at certain points without any real worry of overheat. I took my time and the blade stayed fairly cool throughout, with water dips when needed.
As a note, after I finished regrinding the second side, enough of the stress in warped areas had been released that I had to take one more pass on each side before it was back to true zero. Luckily this occurred within my parameters for edge thickness (.009"), and it was a success without having to lose any more edge in the process.
Total time about 2hrs, working at a semi-relaxed pace.
It was a solid performer out of the box, but after some moderate geometry and edge profile adjustments, it's quite the hot rod.
b
Thought I would share the repair I did for a local customer. Some member of his family (none have come forward to be shamed as of yet) decided a good way to split a bone in roast was with this knife and a mallet. It did not work out too well as you all can see below. This chronicles my evening's diversion in the shop. I had some spare time since my paypal got nuked by the home depot breach, and I couldn't prep shipments. Of course they reversed the charges and restored my balance five minutes before the post office closed today.
This is a fairly nice German made Wustof Classic. I own a couple blades from this series and they are some of my favorite working blades in the kitchen. IME at least, Wustof runs their HT a bit higher on this particular series, than many well known midrange premium production blades that I've encountered. Considering their reasonably thin geometry and higher hardness, they are impressively resistant to different types of edge damage in my experience. I'm pretty sure they run this steel up to the max which from what I understand is about 60rc. That it took this kind of abuse with only a tiny crack, is quite impressive. Solid HT.
Normally I wouldn't recommend a repair like this to a customer if the blade was less than $100 average retail. These guys run about $150, so definitely worth a $50-75 regrind, especially considering that the knife probably could have used a regrind straight out of the box, and had close to the performance of finely tuned custom, at probably half the price. No criticism towards Wustof, just a side effect of production. In his shoes I *may* have chosen to write it off and use it as an excuse for a new knife, but this route is much more wife-friendly, and he will end up with a pretty darned good blade for not much out of pocket (considering it's pretty much trashed).
This is the patient. The main damage extends about 10mm into the blade, with about 2mm of crack in the worst area. There is secondary damage from the customer's (extremely unsuccessful) attempt to straighten the blade before handing it over to me, which extends about 20mm above the edge. Luckily this was fairly light.
I put a fine point sharpie in my compass and used it to trace a line along the edge. This line is about twice the height of the crack. I'm not grinding up to it, just using it as a guideline.
Next I grind up to the top of the crack. This will prevent it from spreading as I straighten the bend. I went about halfway up from the original edge to the scribe, and make a few very minor personal preference adjustments in the profile, slightly increasing the angle of the rear portion to the handle, and slimming the tip while lengthening and smoothing the belly.
There are a few ways this could be done, but this is how I decided on this one. The tool I used is the Knipex Plier Wrench, It's basically a parallel jaw plier or crescent wrench head with plier handles. It's a super handy tool to have... they have a high lever ratio and grab HARD. You can squeeze the corner of a sheet of aluminum so hard with these things that it will extrude into foil.
They're generally meant for bolts and fittings, but also work amazingly for bending and straightening. I don't use crescent wrenches any more, ever.
I adjusted my heat gun to a low end temper temperature, and set it on the table blowing up on the edge of the blade as I worked it. After some coaxing and concentration, I got it into the condition seen below.
I also took it over to my polished mini anvil and did some light peening as needed.
These are the two sides after straightening. One side needs a bit more tlc in the regrind than the other, due to damage by owner's attempt to repair.
I start on the easy side first. There isn't an extreme amount of adjustment to do on this side, so I start out with a fine grit structured belt. They aren't good for everything, but this is one thing I find them to be quite good for. They seem to do quite well for slight geometry adjustments and scratch removal. Not all that great for actual grinding though, IME. This is after the first few light passes, just to see where things were at. Notice how there is a significant roundover in the geometry about 1/8" down the spine. This was not from my platen, It was freshly resurfaced with a large face mill immediately before the blade went to the grinder.
This is the damaged area on side one about halfway through the regrind. The flaw in the factory geometry can be seen much more clearly in this shot. I suspect this is possibly an artifact of the trimming process after forging, but I could be mistaken. More importantly, the blade geometry as a whole needs a bit of fine tuning to be where I like it, especially with having lost a good 1/8" of edge grinding past the crack.
This is after finishing the main blade geometry adjustment for the first side, and beginning to regrind the plunge. I didn't want a goofy transition between my regrind and the factory plunge, so I reground it to align perpendicular to the blade length. The factory grind was done off-angle, and there was no way to get a uniform finish up to the edge of the bolster otherwise.
First side done. Final geometry was done with Norax X45, scratch refinement was done with 400 grit cork. The cork took out the very slight hiccup in geometry that can be seen in the reflection about halfway through.
The opposite side needed a bit more love, So I walked it down from a fresh 3M 947A to Norax X45. It would have been a waste of time to jump in with the finer grit as I did on the other side. This is after some "light hogging" at the lowest grit, and I was edge grinding only. I straightened out the geometry on the next grit up.
This is side 2 finished, including cork belt, and after final sharpening at 2k grit and strop. Shaved a patch clean from my upper leg in one stroke. Just as a final note, I did all grinding with fresh belts on medium low speed. This type of grinding is quite easy on the belts, so the expense of using so many fresh belts isn't an issue, and that way I could concentrate on the edge at certain points without any real worry of overheat. I took my time and the blade stayed fairly cool throughout, with water dips when needed.
As a note, after I finished regrinding the second side, enough of the stress in warped areas had been released that I had to take one more pass on each side before it was back to true zero. Luckily this occurred within my parameters for edge thickness (.009"), and it was a success without having to lose any more edge in the process.
Total time about 2hrs, working at a semi-relaxed pace.
It was a solid performer out of the box, but after some moderate geometry and edge profile adjustments, it's quite the hot rod.
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