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27th January 2013, 01:50 PM #46
Paul, yes, it's honoured more in the breach than the observance, in my experience, but it behoves us to point out that it is a breach of safety rules. Just doing my moderator's job - we don't want the management being sued.
Douglas Bader wrote that his squadron commander once said to him, "Rules are for the guidance of wise men, but should be followed strictly by fools". So it all depends which category we place oursselves in, eh?....
Yeah, wearing gloves around a grinder would not be a brilliant idea, methinks.
Cheers,IW
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27th January 2013, 02:40 PM #47Senior Member
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There seem to be a lot of opinions on how to ideally grind a chisel. You guys are suggesting a hollow ground bevel, not 100% sure what that is. I assume it's some kind of concave primary bevel? On the other hand Paul Sellers, who works primarily with hand tools, sharpens his chisels on 3 oilstones, freehand, with a slightly convex primary bevel, and no secondary bevel. Seems to work pretty well for him. Which leaves me a little confused as to what to do, frankly.
Scary Sharp does seem to eat through sandpaper like nobody's business. That said, the guaranteed flat surface does take atleast one variable out of the equation for me. If I go get the .1x2m $2 rolls of the W&D grits up to 1200 from Bunnies, it should go a long way towards economising the whole thing. I just wish the 1500 & 2000 grit also came on cheap rolls :P
I do intend to get a good marking knife, or else make one. Right now all I have are fairly flimsy arts & craft knives, and stanley knives. I'll see if I can find a decent scrap of metal in the shop to make a knife out of. And I don't imagine that I'll stop buying tools just because I have all the basic ones, but I need to get them first. Then I might get some gouges or something :P
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27th January 2013, 02:43 PM #48
I have a handful of quotes that I trot out with monotonous regularity and that of Bader's is one of them, although I usually phrase it:
"Rules are for the obedience of fools and the guidance of wise men."
That suits my two footed approach and is less diplomatic than your rendition .
Regards
PaulBushmiller;
"Power tends to corrupt. Absolute power corrupts, absolutely!"
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27th January 2013, 02:47 PM #49Senior Member
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Rockwell 150mm Bench Grinder << This one?
Seems a little underpowered, and wouldn't it eat through the chisels pretty quickly? I've never used a grinding wheel before, so I don't know what to expect.
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27th January 2013, 02:53 PM #50
Mooncabbage
There are a handfull of subjects that provoke serious and heated discussion on these forums and the sharpening of chisels and plane blades is amongst the formost. Probably such discussion should go elsewhere and indeed already has done. A search will yield enough results to last until the rain stops .
However the hollow grind to which we are referring automatically will be there as a result of sharpening on the intended edge of a grinding wheel (as opposed to the flat side) on a bench grinder. The advantage is that when the secondary bevel is placed only 1mm or 2mm needs to be sharpened. It is less effort and less wear on your stones, diamond grits or sandpaper. I am not offering an opinion here as to whether that is indeed an advantage: Just stating the alleged benefit.
Regards
PaulBushmiller;
"Power tends to corrupt. Absolute power corrupts, absolutely!"
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27th January 2013, 03:04 PM #51Senior Member
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Thanks for clearing that up Paul I might hold off on the purchase of the grinder for now, but I'll certainly keep it in mind.
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27th January 2013, 04:04 PM #52
Mooncabbage
A bench grinder is an immensely useful tool for any number of tasks particularly if you intend fabricating tools, sharpening or improvising.
The truth is that any grinder will do some sort of a job and in fact the more powerful machines can be easy to use too aggressively when performing delicate tasks such as regrinding chisels and plane blades. The idea is to go gently to keep the blade cool (dipping frequently in water is the tried and tested technique).
However, a low powered machine will stall easily and be frustrating for some jobs and doesn't give you the option of getting stuck into a heavier task. If I was starting with a single grinder I would look at a 200mm grinder with at least a 3/4HP motor (1 HP is better still, but not essential.) That will get you out of trouble for the majority of hobby size projects. The cheaper end of the market tends to have smaller motors.
However, plenty of 150mm machines are sold with a 250W (1/3 HP) motor .
Regards
PaulBushmiller;
"Power tends to corrupt. Absolute power corrupts, absolutely!"
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27th January 2013, 04:08 PM #53Senior Member
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More specifically, besides the sharpening of chisels, what might I use a bench grinder for? You mention the fabrication of tools, could you elaborate and give some examples? I'm interested to know, as something might sound fun. I actually looked at making my own saws, but I think I'll put that off for now.
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27th January 2013, 04:17 PM #54
'Oo's bein' diplomatic now, then, eh??
Yep, sharpening, like religion & politics, can incite more passion than it's worth, Mooncabbage. I think even a rough search of the forums will turn up more info than can be carried in one small head. You have found a means to an end, for the moment, so my advice would be to stick with it until you become dissatisfied with the results of that method.
Since it's still raining, and is going to be for some time, I'll risk stick my neck out a little, & type on.
Should you decide to get really serious about sharpening, there are plenty of things to consider:
1. How to remove a large amount of metal when required, such as rehabbing an abused old chisel, or taking out a deep nick.
You CAN do this entirely manually, on composite or diamond 'stones', with or without a guide, depending on your level of skill and masoschism. If life for you is too short already, you will turn to some sort of grinding machine, either hand-cranked, or electron-burning. You can choose to use wet or dry grinding (though you will probably have to make your own manually-operated wet grinder, which is not all that hard, & plans should be findable on the web).
Many good folk shy away from dry grinding because of the eaase with which you can ruin a piece of god tool steel. However, for the non risk-averse, dry grinding offers the quickest way to remove a large amount of metal. It can be done quite safely, after a bit of practice, but you need to learn to use a light touch, and you [I]must [I]keep those wheels clean. This applues with hand as well as powereed high-speed grinders - you caan toast a chisel on a cranker almost as easily as on the tailed types.
Wheel size may occupy your attention for a bit. The larger the diameter of the wheel, the less of a 'dish' it puts in the bevel of the tool being ground (what Paul was referring to above). The deepeer dish left by a 6" wheel gives a slightly thinner, more fragile edge than a larger wheel, all else being equal. This can be compensated for by grinding a slightly steeper bevel with the small wheel. Sometimes that will have no effect on tool performance, sometimes it might.
'Wet' grinders are safe but slower, tediously so in some cases, because they use a single wheel, and the grit is chosen to give an edge that is almost ready to go. The edge off the dry grinder most certainly isn't for most woodworking tools, especially as the most common grit sizes used for a general-purpose wheel are 60 & 80.
2. Honing
Once you have the 'grind angle' sorted by the means that most appeals to you, you are faced with a bewildering array of choices of ways in which to pass that sharp edge over increasingly fine grits up to vanishingly small ones. As I said before, you want two planes to meet, usually in a straight line (not always, some blades have curved cutting edges). The closer that line gets to a perfect straight line, the 'sharper' the edge. What youa re up against is the grit size of the grinding nedium (which even at its finest, removes metal by scratching it away) and the nature of the steel itself, which is not truly homogenous but has minute hard & softer spots throughout. So you can never get a perfectly straight edge, as a quick look with even a low-powere microscope will show.
Some folk like to take their polishing to levels far beyond what works for me. Received wisdom has it that the higher the polish of the edge, the sharper it is, and usually, the better it lasts in use. Only you can decide when enough is enough for your purposes.
I will offer an opinion here (and am prepared to be challenged by proponents of the opposite view!): I do not like honing methods that involve paper or any material that is relatively compressible. To my mind, using any of the paper stuck to a surface methods, you simply cannot prevent the abrasive material from flowing up a bit behind the edge and causing some rounding over. If done very carefully, you will get only a small radius, but I've come across too many edges that have been quite noticably rounded, as amply demonstrated by a few rubs on a diamond stone. Even stones cause some rounding, because the swarf gets pushed by the edge, or rolls under it when the edge is drawn back, but it is much more minute than that caused by using any compressible honing media. For many purposes, the rounding is insignificant or even desirable. For example, on a plane blade that is slightly pitted on the back, some rounding creates a sort of 'back bevel' that brings the actual edge down into clean metal. The slight increase in cutting angle may be more than outweighed by the better edge obtained. Carvers have told me that the 'duffed' edge they get by stropping on leather strops or wheels is desired & makes the tool easier to control. But the aabsolute least possible amount of rounding is dersirable on the back of a paaring chisel. There are no absolutes!
For me, after the grinding wheel, it's stones only. Diamond? Oil? Water? "ceramic"? You pays your money & you makes your choice. All are capable of producing very fine edges, if you are prepared to work through the necessary series of grit sizes. Each has its merits & demerits in terms of cost, speed of cut, & durability of the working surface. For example, most oilstones cut a little more slowly than waterstones of equivalent grit size, but the surface of waterstones wears away more quickly, so you must watch that. Oilstones tend to clog more easily, especially when usd with thicker oils which will greatly reduce the speed of cSo although they shouldn't nbeed as regular dressing as waterstones, they still need proper maintenance to keep on cutting at their best. Ceramic stones cut fast & stay flat, but they are expensive & the cost vs longevity equation may not suit you.
And so on.
Aren't you all hoping this damn rain would ease up so the dog & I can go out for a while??
Cheers,IW
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27th January 2013, 04:28 PM #55
Sorry the cheapest is a 5" grinder for $32. Smaller diameters create more deeply curved hollows and so a thinner/weaker edge. But - I haven't sat down to any calculations on this - maybe if there is a micro-bevel added then this might not be much of an issue.
The reason I mentioned the hollow grind is that it can help in freehand sharpening to register the bevel of the chisel onto the stone (or paper). Also - what Paul said - as you hone the primary bevel (on a hollow ground bevel) it will only contact at the bottom and the top of the bevel so you can work quicker. The hollow section in the middle will shrink away with repeated sharpenings until it is time to grind again.
And then the microbevel idea is an optional extra.
ALSO ... Do you all think this is right??????? Supercheap have a 75mm grinder for $32
3" Grinder ... with an Alox wheel by the look ...
Rockwell Bench Grinder - 75mm - Supercheap Auto Australia
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27th January 2013, 04:31 PM #56Senior Member
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Lol no. I love the rain, and it's making you post interesting things :P I wish it'd rain here, stupid Perth is too dang hot.
I can see the argument about the roundover with sandpaper, IF it's used improperly, particularly larger grits. Very fine grit sandpaper is so thin, that properly glued to glass with a spray adhesive, it should have negligible compressibility or deviation from the flat. Certainly no more than a stone. With thicker grits the rounding effect is less important, because as you work down the grits, you'll be shrinking that bevel anyway. Also, taking the effort to sharpen BOTH sides of the chisel should help make a finer point, as it's significantly harder to round over when lapping the flat face of the chisel. My personal feeling is you should keep the flat face of a bench chisel atleast as well cared for as the point and the bevel, as that's the face that needs to slip past cut edges when paring etc. It just makes sense, from a physics PoV to keep it as smooth as possible. Thus, I am not too concerned about rounding over the cutting edge with sandpaper. That said, I have seen some people use sandpaper by strapping it to a block of steel or similar, in a vice, rather than actually gluing it down. The movement that allows likely WOULD result in a less than ideal cutting edge.
Feel free to comment :P
EDIT: Tiny grinders are tiny, and I could probably get away with one in my shop, but I don't want to spend the money until I have more than one use for it anyway :P
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27th January 2013, 04:34 PM #57
I don't think it can be underpowered AND eat through the chisels OK ... probably could be ...
As opposed to what a metal-worker might use a grinder for ... grinding a (basically healthy) chisel involves very little pressure. The less pressure the better ... almost.
Cheers,
Paul
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27th January 2013, 04:37 PM #58Senior Member
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Actually I really should have asked about the wheels/stones on those things. Having never used one before... What's the deal with those? Do I get a bunch and change them out? Do I just get two general purpose ones, like my trojan stone has two sides? Help me Obi-Wan Kenobi!
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27th January 2013, 04:43 PM #59GOLD MEMBER
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I suggest that for bed time reading, you try "Star's Sharpening Journey."
That is total show-and-tell for what i continue to do.
This is a whole lot like shaking hands with an octopus.
One thing at a time, yes?
Buy a few basic shaping tools. See what a mess you can make in some easy wood.
Look. You can't just jump into this at full throttle. The hell of it is, there's a learning and experience slope that you just can't get around. You have to bang around, mess around and then . . . . you ask questions here with a bazillion people to help you move on.
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27th January 2013, 04:46 PM #60Senior Member
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It never hurts to be informed about your options though :P Actually I'm pretty sure I'm going to stick with Scary Sharp for now, I'm mostly wondering if there are other cool things I can use a tiny underpowered grinder for, like tool making or whatever.