Good stone for D2.

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ChefKnivesToGo
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Good stone for D2.

Post by ChefKnivesToGo » Fri Jul 13, 2018 2:13 pm

I have a guy that called me that is sharpening a big cutting tool in a factory. He's cutting a type of polyurethane that looks like a big wheel of cheese but is close to the consistency of one of those foam pad beds you see on TV.

The problem is the edge gets ragged over the course of a shift and starts to tear the material. He then uses a King 1200 to touch up the blade in place (It's about 5 ft long), using the stone in his hand as he cleans up the edge. He sends the blades in for resurfacing every 3 weeks.

So he wants to improve the edge. I haven't used D2 very much and want opinions on what might be a better stone to use for him. He's willing to do a multiple stone progression and his operator is keeping the stones flat and I assume they're perma soaking the stone but I didn't ask him about this. I hope he's not using it dry.

Any suggestions? I have a couple of ideas.
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gladius
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Re: Good stone for D2.

Post by gladius » Fri Jul 13, 2018 2:49 pm

If a King 1200 is sharpening it it up then most any brand will work...Shapton, Naniwa, etc. A splash & go stone might be easier to use. Also a higher grit finish may last longer or a (coarser grit) - you would need to experiment.

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Re: Good stone for D2.

Post by Lepus » Fri Jul 13, 2018 2:57 pm

Diamond plates seem like they would be the easiest option, to be honest, maybe even the CKTG combo plate. It would make lubrication easier, to be sure. I'd think Shapton Pros would be good choices, too. They certainly handle SLD well.

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Re: Good stone for D2.

Post by ChefKnivesToGo » Fri Jul 13, 2018 3:21 pm

gladius wrote:
Fri Jul 13, 2018 2:49 pm
If a King 1200 is sharpening it it up then most any brand will work...Shapton, Naniwa, etc. A splash & go stone might be easier to use. Also a higher grit finish may last longer or a (coarser grit) - you would need to experiment.
I agree with the splash and go.

I also think a ceramic based stone would do better with this steel.

I also think a 2 stone progression would do way better keeping the edge smoother so it doesn't rip the product.
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Re: Good stone for D2.

Post by ChefKnivesToGo » Fri Jul 13, 2018 3:24 pm

Lepus wrote:
Fri Jul 13, 2018 2:57 pm
Diamond plates seem like they would be the easiest option, to be honest, maybe even the CKTG combo plate. It would make lubrication easier, to be sure. I'd think Shapton Pros would be good choices, too. They certainly handle SLD well.
I thought about diamond plates as well. I just worry that you would wear them out too quickly. Also they tend to leave a toothy edge and I think they need a smoother cutting edge.

Shapton Pro stones would be a good option. I wish they had something between the 320 and the 1k. Maybe a 1k-2K or a 1K-5K would be a good combination.
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Re: Good stone for D2.

Post by Lepus » Fri Jul 13, 2018 3:34 pm

With how a factory worker might use them, you're probably correct. Even the sturdier ones will wear fast with a lot of pressure, which might be best in this sort of setting.

If they're usually able to dress it with the 1200 King they can definitely start with the 1000 Shapton. That might be all they needs and I bet will improve the situation immediately; carbide formation in D2 is anecdotally large and the King isn't going to have been hard or abrasive dense enough to be suitable. The Shapton will be faster and better able to shape the blade. Depending on how much time they spend on the task every day they might even want a 220 just to initially shape everything.

The 2k might work well as a finish for this use, and in fact I know the Shapton 2k is great for D2 both from using it myself and from reading about them in the context of outdoor knives. If they are willing to try it the 5k would be ideal if a finer edge actually does work better.

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Re: Good stone for D2.

Post by jacko9 » Fri Jul 13, 2018 4:04 pm

You might want to ask what finish they put on the blade when he sends it in every three weeks. The King 1200 might be necessary to clean debris off the edge and it might not be giving him the necessary edge refinement that the blade needs. The edge getting ragged over the course of a shift sounds like the breakdown of a very refined edge so after the course stone perhaps a two step Shapton Pro 1500 and 5000 finish might work.

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Re: Good stone for D2.

Post by gladius » Fri Jul 13, 2018 4:07 pm

If a finer edge works better, I'd be inclined to use a scythe stone. They are very effective used in the field to touch up the edge. I use one on my sickle in the garden.

https://onescytherevolution.com/whetstones.html

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Re: Good stone for D2.

Post by Jeff B » Fri Jul 13, 2018 4:10 pm

For a polyurethane foam like material I would think a higher polished edge would work and last better. I'd sent him an SP1k and 5k to try. If he likes them he might want to try taking it up to an 8k later, like in a Naniwa Snow White. He may even get to where he doesn't have to sent it out as much to be resurfaced.
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Re: Good stone for D2.

Post by ken123 » Fri Jul 13, 2018 5:12 pm

I think this one is easy - Shapton Glassstones. These stones were SPECIFICALLY designed for D2 steel so they would be a first choice. You could either do a sequence or go for your favorite grit. There are a few D2 steels so you might consider alternatives too. Start with GlassStones :) Most everything should be an improvement over a King.

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Re: Good stone for D2.

Post by lsboogy » Fri Jul 13, 2018 6:44 pm

One of our machinists has started using shaptons on some of the tools in the shop. They used Arkasas stones for years, and I brought in 2K, 6K, and 8K stones after he looked at my knives one day outside while I was cooking for the shop. He ended up buying a full set of stones (really coarse to about 16K, and I think even some of the radiused stones he uses now are shaptons). Aerospace machine shop - if you have been on a commercial or military plane, we have parts on it. Now Scott has a large drawer of stones - probably 25 of them - I'm not allowed to touch them though

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Re: Good stone for D2.

Post by jacko9 » Fri Jul 13, 2018 8:44 pm

ken123 wrote:
Fri Jul 13, 2018 5:12 pm
I think this one is easy - Shapton Glassstones. These stones were SPECIFICALLY designed for D2 steel so they would be a first choice. You could either do a sequence or go for your favorite grit. There are a few D2 steels so you might consider alternatives too. Start with GlassStones :) Most everything should be an improvement over a King.

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I like the Shapton Glass and I bought a lot of them from the Cktg store. I think the 2K and 8K could be a winning combination (even though I use my Shapton Pro 5K in between).

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Re: Good stone for D2.

Post by ChefKnivesToGo » Sat Jul 14, 2018 9:33 am

jacko9 wrote:
Fri Jul 13, 2018 4:04 pm
You might want to ask what finish they put on the blade when he sends it in every three weeks. The King 1200 might be necessary to clean debris off the edge and it might not be giving him the necessary edge refinement that the blade needs. The edge getting ragged over the course of a shift sounds like the breakdown of a very refined edge so after the course stone perhaps a two step Shapton Pro 1500 and 5000 finish might work.
I thought of that too. I'll ask what kind of process they're using when they send it in.
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Re: Good stone for D2.

Post by ChefKnivesToGo » Sat Jul 14, 2018 9:55 am

ken123 wrote:
Fri Jul 13, 2018 5:12 pm
I think this one is easy - Shapton Glassstones. These stones were SPECIFICALLY designed for D2 steel so they would be a first choice. You could either do a sequence or go for your favorite grit. There are a few D2 steels so you might consider alternatives too. Start with GlassStones :) Most everything should be an improvement over a King.

---
Ken

---
Ken
They might be hard to handle for the operator since they're so thin but I'll ask them about this.

Here is a look at how they're using it which will tell you guys a lot about what's going on. Basically, they're taking a large cake made of dense foam and thin slicing it against this cutting edge.

Image
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Re: Good stone for D2.

Post by jacko9 » Sat Jul 14, 2018 10:39 am

From the way he is using the stone I would imagine that using a Atoma 140 to flatten it would be very helpful since I can imagine him putting a lot of ridges into the stone face. Does he run the stone over the back edge of the bevel to knock down any burr? Interesting problem.

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Re: Good stone for D2.

Post by lsboogy » Sat Jul 14, 2018 10:41 am

For a tool that big the need a precision grinder. We have shears for 12' (3m) sheets that they take the blades off of and grind them when they need. I have seen the smaller sheer blades on the grinder as well. A good grinder makes our stone work look messy - I deal routinely with finishes (bearings) with 50 millionths of an inch (bearing code can get even tighter) tolerance for overall, and 50nm surface finish. Guy needs to find a good grind shop - we can cut 3/8" aluminum on our shears and use them every day

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Re: Good stone for D2.

Post by lsboogy » Sat Jul 14, 2018 11:13 am

Precision grinding is used in my field as well -MEMS. We buy silicon wafers and specify step and wedge for them in angstroms. These are done center less grind - my idea of a large step (how high an edge can be) is 30 angstroms - about 10 atomic layers of silicon - about 1/10th the size of a martensite grain in steel, so a good grinder can put you down to single planes of steel (martensite, cementite, austentite grains) easily. We use devices made of stuff like Ken does - on a tangent note, maybe the guy should send out his blade for heat treat as well.

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Re: Good stone for D2.

Post by ken123 » Sat Jul 14, 2018 11:33 am

So there are a few extra variables.

What hardness is the d2 blade? A stone harder than a King would work well here. If the d2 is at a low hrc this might explain why a king is working. Even so the king should be flattened often.

What is the sharpening angle? Many shears are ground at very coarse angles like 45 degrees per side or even 90 degrees total. Specifing angular precision requirements, microbevels etc would be helpful.

Is it a single or double bevel? Looks like a single bevel much like meat slicers

Can the blade be removed from the device? This allows for many other choices including belt grinders , angle grinders etc that wont fit in the space provided while the blade is installed..

In addition to Glassstones there are some other choices Ill ignore for now. Even with glassstones you can add a holder to the stone for thickness and operator comfort.

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