Thread: Sigma Power Select II Ceramic Water Stones

Rob, firstly about the PM-V11 ...

The factory lap the backs of all their blades much flatter than you could ever achieve. Anything that you do to flatten the back will degrade it.

The surface is finished at the equivalent of 4000 grit. The grey does not alter this. I have gone straight to a 12000 grit waterstone, and polished it to a bright finish in a few strokes.

Secondly, the ruler trick. DON'T DO IT! It is NOT for chisels. It is for plane blades, and it is for beginners. It's a fine strategy - this was one of David Charlesworth's very clever ideas, but it is for beginners.

The Ruler Trick is essentially a back bevel, which is created using a steel ruler for a spacer. It creates a 0.3 degree back bevel on plane blades, which ensures that the back of the blade is polished. Because the angle is so low, it does not impact on the cutting angle. One must not do this on a chisel blade since that would remove the coplanar back.

Point three. The issue I have with lifting a blade to add a secondary bevel is that the angle inevitably gets higher and higher, and then too high to cut. What I do is hollow grind all my blades, at the angle I want (generally 30 degrees for everything), and the sharpen directly on the hollow, which acts as a jig and maintains the angle. This is a little more set up time (although not on my system), but saves time thereafter. The problem with many sharpening strategies is that they are focussed on getting a sharp edge, while I believe that re-sharpening to sustain a sharp edge is much more important.

This is my sharpening set up, which has evolved over about 30 years. I wrote this some years ago, and it has not altered. I am very happy with it: http://www.inthewoodshop.com/Woodwor...ningSetUp.html

Regards from Perth

Derek

p.s. PM-V11 does not alter hardness as you work it. The "PM" stands for "powdered metal", and this creates a very - incredibly - consistent steel.

Yes Derek I know not to lift chisels and I haven't ever done that . I said it above as well and its still there to be read .

You missed it obviously .

I have only ever done it on plane blades where it speeds up finishing the stone work and doesn't matter .

I was interested to read through your in the wood shop sharpening write up last week . Just out of interest . I'm sharpening all right , have been for years and am running low on hairs on my left arm atm . I was telling a visitor to my workshop Ill be trying for the hairs on my Ball Bag soon .

Edit
The thing with me is , in a long line of planes on the shelf , the only ones with a straight blade is a no 7 and 8 jointer. Resting on the hollow is easier with straight blades , resting on the hollow works with curved blades but gets harder to hone when your sweeping through a curve as well . Depending if its a full radius or a partial with a more pronounced curve at the ends as well . It gets trickier . So as long as I'm getting a fine burr edge and taking it off and getting the blade back on the job is what really matters .

The PMV- 11 I have just bought is for one of my no 7 planes . The Bedrock jointer . If there is one job I want the longest lasting edge for its jointing table top boards . A weekly occurrence in what I do .
Some of them a long 3 Meters and 50 mm thick Oak with 6 edges to be accurately jointed, slightly hollow in the middle and sitting up straight on one another in the vice with no rocking from any twist in anything .

Sometimes its a whole extension tables worth . I look forward to seeing how long this blade lasts doing that sort of thing .


Rob

Mmmm .. Rob, it sounds like I have offended you. That was not my intent. You are very experienced, far, far more than I. However, you asked about about PM-V11 and commented on using the Ruler Trick as if you were not aware of it. My apology if you believe that I have told you how to suck eggs.

Regards from Perth

Derek

Ha Ha Derek . No I'm not offended . Not like before So don't worry about it . Your not any way are you lol .

Rob

While there is no doubt the LV PM-V11 blades arrive 'dead flat', it's pretty hard not to touch that back for the life of the blade, is it not? I certainly don't waste precious elbow grease on the back of a new blade unless there are obvious grinder marks, as there are with many (most?) other brands. I don't worry about the burr on preliminary stones, but I always finish off with a short rub of the back (on 8,000 grit) just to make sure there is no tiny burr left, which puts a pretty shine on the end very quickly. Hard to alter the habits of a lifetime. The grey surface the blades arrive with seems to resist corrosion so I prefer to retain it as much as I can by rubbing only the end of the blade over the stone, but I do that very carefully so I don't cause any (detectable) rounding.

My sharpening skills have grown in a series of plateaux - improvement in technique & better media entered the scene at various stages & I'd think "this is as good as it can be". Then sometime later I'd find ways to do a bit better. The increments get smaller as time goes by, but they still happen, so I'm resigned to the fact that I will go on approaching, but never reaching "perfection". Come to think of it, I could say that about everything I do....

Cheers,

I have gone through stages as well, all the gadgets in the world and arrived at a simple & very quick method these days. The introduction of the CBN wheel was pivotal for me in that process.

The CBN sounds good Chris . Do you think it needs to be run slow at 1480 or does it work just as good at 2850 ?
Im thinking of getting the wheel but wondering if I have to have another grinder in the workshop ?
I do like slow grinding . Variable speed to much slower would be a nicer thing than just a stuck at half speed thing maybe .
Rob

Rob, have you got a 3 phase grinder? if so that can use a VFD to control speed. I haven't used a CBN wheel on a full speed grinder but others have and may chip in here. I have a 180 grit x 200mm wheel on a half speed grinder and when it was new it simply ripped off the metal so fast it did not have time to get hot, Matt (Simplicity) saw this happen. Since then the cutting action has become far less aggressive and I would not mind a coarser wheel at half speed and mine I think would now work better on a full speed grinder. If I had a 3 phase grinder I would simply wind the speed up at this point in the wheel life. VFD's are relatively cheap for this kind of purpose, cheaper than a new grinder anyway.

Plus one for CBN, I'm a total convert. They sure take the worry out of grinding tool steel. You can burn things if you are heavy-handed, but if you take it sensibly you can grind all the way to a sharp edge with little fear of overheating. Mine's a bit coarser than Chris's, but still leaves a surface that polishes quickly on the honing stones.

I have a "half-speed" grinder, which the CBN wheel makers do recommend, but plenty of folks use them on "full speed" machines. Chris, you're the engineer, can you comment on my hypothesis that with a full-speed grinder, if you pass the blade across the wheel at twice the speed you would use with a low speed grinder (applying the same pressure), you should create the same amount of heat in the blade? As long as you work at a rate that allows sufficient heat dissipation between strokes, there should be no greater danger of burning your blades or dislodging the abrasive particles.

The biggest dangers from grinding wheels of any description are glazed wheels and heavy hands. I use a carborundum wheel on the other side of my machine for rough stuff like sharpening mulcher blades. They do a pretty good job as long as they are dressed regularly and not forced, but I've seen blades blued very successfully with carborundum wheels on hand-cranked machines going much slower than my grinder, for those very reasons. That's another plus for CBN - they don't glaze, which is just as well, 'cos I don't know how you'd clean one. I hope no-one has ever tried using a star-wheel or diamond dresser on their CBN!?

Cheers,

Originally Posted by IanW

Chris, you're the engineer, can you comment on my hypothesis that with a full-speed grinder, if you pass the blade across the wheel at twice the speed you would use with a low speed grinder (applying the same pressure), you should create the same amount of heat in the blade? As long as you work at a rate that allows sufficient heat dissipation between strokes, there should be no greater danger of burning your blades or dislodging the abrasive particles.
Cheers,

Ian, I wish I was an engineer but I failed kindertarten so never got to Uni. A lot of people use CBN on full speed grinders and it sort of stands to reason that your supposition is correct. A good way to test for heat build up is to rest a finger on the blade close to the wheel. I have never used coolant with the CBN and it sure makes less dust than a friable wheel. Back to the Matt story, I was at Dave's place in Dooen and took the grinder to show people what a CBN wheel was and what it could as I had just got it. He gave me a chisel to sharpen and it looked like it had been driven into a nail multiple times and two minutes later the picket edge was gone and Matt was a convert. My wheel would not do the same job at the same speed nowadays but it is still way quicker than a friable wheel. In a production workshop I reckon a CBN wheel would pay for itself very quickly, no dressing wheels and far faster with no dust to breath in.

Originally Posted by Chris Parks

Rob, have you got a 3 phase grinder? if so that can use a VFD to control speed.

I do have an old 3 phase grinder somewhere Chris . An old Aussie made thing I think . Ive seen heaps of them over the years , cant remember the name atm . An abbreviated three letter name . Its in one of my containers and when I find it Ill Have to put a pic up to find out if it can run on VFD .

Rob

Edit . I think its a GMF bench grinder

Originally Posted by IanW

Plus one for CBN, I'm a total convert. They sure take the worry out of grinding tool steel. You can burn things if you are heavy-handed, but if you take it sensibly you can grind all the way to a sharp edge with little fear of overheating. Mine's a bit coarser than Chris's, but still leaves a surface that polishes quickly on the honing stones.

They sound great Ian . There is a few to choose from as well . The Vicmarc look to be pretty special with the 40mm face and side .

Sanding & Grinding: CBN Grinding Wheels

Do you know, are they the Bees Knees of CBN wheels?

Rob

Originally Posted by auscab

......The Vicmarc look to be pretty special with the 40mm face and side .

Do you know, are they the Bees Knees of CBN wheels? ....

Well, mine just happens to be a Vicmarc, Rob, but since I have not used any other, I can't compare it with other brands. The cost is pretty similar, wherever you look (or they were when I was buying mine), which leads me to suspect many 'brands' emerge from the same factory. I plumped for the Vicmarc because they are not that far away from me, and I like to support local firms where I can (though the wheels are probably made off-shore!). It's lived up to expectations, and runs true. I ummed & arred over what grit size to get, & eventually decided on the 80 grit. That turned out to be the right choice for me, because I never take a tool directly from grinder to wood, but busy turners who do would find the 180 a better bet.

Most seem to include the grit on the side, though I noticed a few cheaper wheels didn't, & you had to read the fine print to discover the fact, but it was a 'key selection criterion' for me, because I use the side of my wheel a lot. I'm sure we've all been admonished not to use the sides of vitreous wheels, just as I'm sure most of us do from time to time, but it's comforting to know I'm not breaking the rules anymore when I use the side of my wheel....

Chris, as you say, a finger or two applied to the tool about 10mm back from the edge being ground makes a good temperature gauge as well as steadying the blade as you pass it across the wheel. I make even, light passes and pause longer between each pass if I feel things warming up too much. You probably get a bit more heating with the finer grit wheel you have, but I rarely need to dunk any tool when grinding on my CBN wheel. I've had it long enough now I tend to forget how cool it cuts even compared with an AlOx (white) wheel, which had been my standard for donkey's years before the CBN came into my life; I wore-out quite a few of those! I still use a grey carborundum for 'coarse' grinding' to preserve the CBN as much as I can, & it often catches me out because I forget how much more heat a vitreous wheel generates even when freshly-dressed...

Just a word of warning to those who have trouble with grinding - a CBN wheel is a huge help, but you can still ruin tools quite successfully if you are heavy-handed, & probably shorten the life of your wheel to boot. My uncle, who was a fitter, only knew grey wheels, or at least I never saw him use anything else, and always on 'full-speed' machines. He kept wheels dressed, was incredibly deft & quick, making a few quick, accurate passes over the wheel - the job was done in the blink of an eye & never a hint of blueing to be seen. He'd probably call me a sissy for using a CBN wheel, but my excuse is I'm primarily a woodworker & haven't got the time or desire to develop the level of skill he had.

Cheers,

Rob, dig out the grinder & see if a CBN wheel can be had for the shaft size. If that works give me a call and I will organise a VFD for you. I bought mine from CWS because it was easy and back then there was little option. The Tormek tool rest that Derek uses is a good thing as well but you may not need it.