Grindstone Roughness & Smoothness

[staysharp]

I would like to know if by sharpening on the fast grind 200g wheel after a few minutes of sharpening the grind wheel seems to become smooth again to the touch and needs the stone grader to roughen up the surface again is this possible that it does happen.
Look forward to a reply
Thanks

[Dakotapix]

My answer is yes. If I'm doing some heavy duty regrinding, I find it helpful to "freshen" the surface of the wheel with the 200 grit stone grader. I spent some time recently trying to rescue a plane iron that had serious pitting near the cutting edge. I probably regraded the stone three or four times during the process.

However, you also may want to consider truing up the wheel with the diamond truing jig. That will give you a really nice cutting action.

[Jeff Farris]

Depending on the shape of the tool and the composition of the steel, it may be necessary to grade the grindstone every few minutes. Flat bevels and hard metals (think plane irons, skew chisels and planer blades) smooth the stone quickly. Use the grader frequently to keep the stone cutting. This is much less of an issue on shaped tools, like gouges.

[Herman Trivilino]

I would like to know if by sharpening on the fast grind 200g wheel after a few minutes of sharpening the grind wheel seems to become smooth again to the touch and needs the stone grader to roughen up the surface again is this possible that it does happen.

Yes, this does happen to me, too.  The coarse grains get broken into smaller grains, and tiny pieces of metal get lodged in the grindstone, too.  Frequent refreshing with the coarse side of the stone grader is sometimes required.  Use the corner of the stone grader, as shown in this drawing, when necessary.


 

[pcoleviolin]

Hi. I am new to this forum, and have just recently bought a T-7 40th. anniversary machine. I've been using it to grind and sharpen my chisels, planes, and a couple of carving gouges. I think I can offer some first impressions and maybe even some advice. I am a violin maker so I have a variety of tools to work with here. I use the T-7 along side a couple of Japanese bench stones, and I love the fact that my sharpening is now all water based, with the exception of oil on the leather for honing.

I find this topic of the grind stone abrasiveness interesting, and after studying the excellent manual and using the machine for a week I think it might help if I suggested something about the stone grades (for the standard stone). I find that the stone grader block is generally useful in the sharpening stages for tools. It offers good sharpening and final sharpening stages for tools like kitchen knives and probably turning tools as well, though I don't have a lathe (I have used a machiner's lathe for exotic hard woods, but not in my shop).

The diamond truing tool is a MUST, and frankly am a bit surprised the T-3 doesn't come with it. Anyway, the manual explains how important it is to maintain the wheel true. Yes, I do it after every use of the T-7, even if just the slightest bit to clean it up. Others have already mentioned that the trueing tool leaves some deeper scratches in the wheel, and I've also found as others have, that these scratches (particularly when truing at the rate of 30 seconds across) to make the wheel grind steel very quickly. The manual also mentions truing a bit faster, up to about 90 seconds to cross the wheel. You want to do this as slowly as possible without inducing vibrations to the truing tool. At this point the wheel will grind well, but just not as quickly as the 30 second truing.

Then I've found there is a pretty good gap between the 90 second truing and the rough side of the Stone Grader, and I would advise against jumping from the truing tool to the stone grader at every grinding/sharpening session. Instead, plan ahead. Do some rough grinding to a few tool at the same time, and then use the stone grader for your selection of tools. If you find that the rough side of the stone grader is a little too fine, a good solution is to use a medium grade diamond plate instead. Just hold it on the stone for a few seconds and do a bit more grinding. It won't be as coarse as the truing tools gives, but it's somewhere in between.

If you go from the truing tool to the stone grader for every single tool, I feel that you will be wasting a lot of the stone material. Instead, plan ahead, and grade the stone as accurately as possible for the tool requirements. Also, the manual does a good job of explaining pressure. I found this extremely useful as well, even when touching up on my Japanese stones or the leather honing wheel. A smaller tool requires a lot less pressure, and for really wide blades it's really not so much about pressure as it is about stone grade.

So my observation has been that there are about "five" different grades which can be set on the stone. 1. With the truing tool across at 30 seconds. 2. Truing tool at 90 seconds. 3. Medium grit diamond plate. 4. Stone grader on the rough side. 5. Stone grader on the fine side. And you could add even "six" if you briefly take a Nagura stone to it in the end, making it almost unnecessary to touch up on anything finer like a 6,000 Japanese stone.

Anyway, all this learning and grading has been very helpful to me. So keep your stone fresh, and keep your Tormek clean and it should reward you with many years of service. All it takes is a few seconds here and there. Remember that every time you use the truing tool or the stone grader or diamond plate it does remove material from the stone.

[Herman Trivilino]

Hi. I am new to this forum, and have just recently bought a T-7 40th. anniversary machine.

Excellent choice, pcoleviolin.  Welcome to the forum.  Those are great tips.  I especially like the  Nagurs stone tip.  I have a hard time getting that really smooth grindstone surface for those really hard steel knives that chip with a coarser grain.

[Ken S]

Welcome, staysharp and picoviolin.  I second Herman's positive thoughts.  Using a nagura stone never occured to me.  What an intriguing idea!  I also like the idea of grading with different diamond hones. 

Please keep us posted.

Ken

[pcoleviolin]

Thanks for the kind welcomes. I'm not sure how much I can contribute here, but it's fun to participate a little.

Just to clarify a bit from my earlier post, I wouldn't use all of the "grades" of the stone from start to finish with every tool. It would depend on the blade and the application. Also I'm not sure how effective the Nagura stone is. It does seem to help a little, and maybe that's enough, but at that point the fine side of the stone grader seems to generally be smooth enough for most purposes. Applying different pressure to the stone grader and whether you hold it in one place or move it around (and how quickly) on the surface can create a little bit of difference. I try to feel and listen to what's happening (another benefit of having a quiet machine). The pressure difference might help with the HSS turning tool. My first thought about sharpening very hard steel was to try a slightly coarser grade but with a lot less pressure on the tool, especially on gouges which contact the stone along a very fine edge...

I remember when I used to do some lathe work that I didn't even bother putting much of a shine on the tools. I'd just go right from the high speed grinder to the wood. I actually felt that it helped to have a litte bit of a bur on the tool.

As a side note, I've been shaving with an ice-hardened stainless steel straight razor, and I've found it very much of a challenge to hone and strop well. But my hunch is to be wary of the pressure. I tend to think that applying more pressure on finer grades is the way to go, but I think it's actually the opposite. Less pressure on coarser grades seems better. Hopefully this helps.

[Herman Trivilino]

 Jeff Farris, our fearless leader here on the forum, has often taught us to apply time and pressure with the stone grader.  You might notice that a couple of minutes spent with the fine side can make the grindstone very smooth.  Others have mentioned it feels like glass, but I always feel "pimples". 

Likewise when the grindstone gets glazed over it takes a couple of minutes with the coarse side of the stone grader, at high pressure, to get the cutting action back.

Jeff has recommended developing a concave surface on the smooth side of the stone grader, and I think a round over on the corners of the coarse side, too.

[pcoleviolin]

The manual says 20-30 seconds with the stone grader, so I am sceptical about a couple of minutes... Also slightly rounding the stone edges...  I'm always wary of grinding away too much of the stone material, and putting too much pressure on the bushings for too long. I was wondering about the knife jig though, when going around the tip of a knife. I think it works better if you lift the handle as videos show, but the instructions that came with the jig show something else. But that is perhaps discussed in another thread.

[Herman Trivilino]

Well, pretty much all this stuff has been discussed before, but those discussions are scattered all over the place.  Very hard to find.

Jeff Farris is an experienced demonstrator of the Tormek.  That's a vast understatement given his many years of experience in both the use of the Tormek and in giving advice and direction to other users.   I have found his advice to be spot on.  In one of his videos (you can find lots of them) he recommends that lifting technique for the knife jig.

Personally, I'm finding that attaching a small piece of rigid plastic, wood, or metal to the base of the scissors jig is a far better way to sharpen knives of all sizes.  Once I added a piece of adhesive-backed felt I was in business.  The other day I sharpened four large kitchen knives for my son.  One set up of the jig was all that was needed for all four knives.  I noticed that the grindstone had to be super fine for one of those knives because a view at 40X showed the edge was chipping.  Had the finer grit been unsuccessful I would have had to go with a more blunt edge angle.

[pcoleviolin]

I agree. Find what works best for you. That's why there are so many different experiences to discuss.