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time for a better sharpening system

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I currently have the oneway wolverine shapening jig and use with your run of the mill hardware store grinder. I noticed a referance in previous posts to slow speed grinders and on vendor site white grinding wheel. it is time for a new sharpen system. I am open to anything any advice ??
 
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As long as you're considering a change...

Sean,

A slow speed grinder is easier for most of us to use for sharpening purposes. If you're shaping the metal, a high speed grinder is nice to have. But woodturners only need to take off a very small amount of metal when they sharpen. Slow speed grinders excel in this environment. However, using a jig and/or a light touch, you can sharpen just as well with a high speed grinder -- it's just harder for those of us who haven't developed a light touch.

What's more important than the speed of the grinding wheel is the quality of the wheel. The gray wheels that come with most grinders are designed for shaping mild steel. They are durable and withstand heat well. The white aluminum oxide and other friable wheels are designed to work with the high speed steels used in modern turning tools. These wheels run cooler by wearing away faster -- constantly exposing "fresh" parts of the wheel surface, thereby preventing the wheel from becoming loaded with used grit and metal residue. This makes it easier to produce a good edge using the newer wheels than with the older gray wheels. Still, all things being equal, you can get your tool just as sharp with a gray wheel as with one of a different color.

Controversial opinion starts here: What's more important than the color of the wheel or the speed at which it spins is the coarseness (or fineness) of the wheel. A typical high speed grinder might come with 36 and 60 grit gray wheels installed. In contrast, the slow speed grinder from Woodcraft comes with 60 and 120 grit white wheels. The new CBN wheels from d-way tools come in 80 and 180 grit versions. A Tormek's wheel cuts at 220 grit or 1,000 grit. The finer the wheel, the sharper the resulting edge (all other things being equal).

None of the above should be controversial. What is controversial is the opinion that using a finer wheel, such as a Tormek's 1,000 grit wheel, is worth the effort. Many turners strongly believe that the edge they get off their 80 grit (or 60 grit) wheel is good enough and that any effort to refine the edge beyond that (through honing or through the use of a finer wheel) is wasted. The argument is that the serrated edge produced by an 80 grit wheel cuts better and lasts longer than the more polished edge resulting from using a finer wheel or from honing. Or, at least, they argue, the sharper edge produced by a finer wheel is not as durable as the edge from an 80 grit wheel.

I don't buy either of these arguments. I believe a sharper edge cuts better and lasts longer. My personal approach is to use a slow speed grinder to shape my turning tools and a Tormek to sharpen them. Unless there's a nick in the edge, I simply make a couple of passes on the 1,000 grit wheel, a pass or two on the leather honing wheel, and I'm back to turning -- with an edge that's far sharper than I could ever get from my high speed grinder. But, there are lots of very good turners who disagree strongly with my approach. They're just wrong, that's all. ;)
 
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I currently have the oneway wolverine shapening jig and use with your run of the mill hardware store grinder. I noticed a referance in previous posts to slow speed grinders and on vendor site white grinding wheel. it is time for a new sharpen system. I am open to anything any advice ??

Slower is more forgiving of operator error. Twice as much grit dragging by in the same time interval is capable of removing twice as much metal. Coarser grits are capable of removing more metal in the same time as finer grits,too. After that, it's how hard you press. Pressing builds heat, which is not a player with HSS, but it also cuts to max depth with whatever grit you're using. Sharpening, to me, is removing the least amount of steel necessary. So slow, fine, and using the tool as its own guide to get full "feel" for least pressure is the way I do it.

Physics plays a part in the difference as well. A bit heavy on one side of a high speed wheel rattles the setup more than a low, and the higher energy available makes it possible to waste a lot of grit that might have stayed for another rotation with a slower velocity. Also a factor with the "friable" wheels which disappear into piles of sand much more rapidly than those more firmly constituted. I have been using SiC wheels for the past eight years or so, and really appreciate them.
 

Bill Boehme

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Slow is relative. Two pole motors run at about 3550 RPM and four pole motors run at about 1750 RPM. The difference is a factor of approximately 2:1, but neither is truly slow. Turners prefer the four pole motor because it runs smoother and nothing is really gained by running faster than that.

David, the standard Tormek stone is 220 grit and not 1000. I have both a Tomek, which I have had for about 12 years, and Delta four pole industrial grinder with SG wheels. The difference in time between the two to sharpen a bowl gouge is a nit. For sharpening a skew the difference is rather significant. Howeverthe results of using the Tormek to sharpen a skew is so much better than using a dry grinder that I tolerate the longer time that it takes. Since my pants are not on fire when I am turning, a few minutes difference doesn't bother me.

Some woods will dull a bowl gouge in short order. In cases like that I often just use the bench grinder. Otherwise, I generally use the Tormek because I have satisfied myself after all these years of use that the edge stays sharp much longer.
 
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Woodcraft Grinder

Does anyone else have experience with the slow speed grinder from woodcraft for $125 that Edward is talking about? I need a new one and It sounds too good to be true.
Robert
 
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HTML:
Does anyone else have experience with the slow speed grinder from woodcraft for $125 that Edward is talking about? I need a new one and It sounds too good to be true.
Robert


I read somewhere that the newer grinders were having problem with the motor overheating. I can't remember what forum I saw that on, maybe SMC. I have had one for a few years with no problems.
 
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I use the Wolverine system with my 1725 rpm grinder and recently purchased a "green" wheel for a lot less money than the Norton SiC. While I don't think much of their plastic bushings and have had to order a replacement wheel at the mfg.'s expense, I am having a machine shop make me an accurate bushing so I don't have to worry about it. The finish achieved with this "green" wheel is nearly as good as honing, right off the wheel. For me, being old and lazy, it is well worth the $60+.
 
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I was chatting with Jimmy Clewes about grinding wheels. He prefers the cheap 40 or 60 grit ones from one of the big box stores. He goes through 8 to 10 a year. I was doing my usual rant about how much better they are than any other wheel out there, and when I bought up the 'there is no way they will ever blow up on you' topic, his eyes lit up. I might have to try one he said. To me it is like variable speed. Now that I have it, I can't imagine not having it.

robo hippy
 
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Does anyone else have experience with the slow speed grinder from woodcraft for $125 that Edward is talking about? I need a new one and It sounds too good to be true.
Robert

I have that grinder...
had problems with wobble when I got it. WC sent me some machined washers (rather than stamped) and it resolved the issue.

Other than that it is fine.
 

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.... a lot less money than the Norton SiC.

......I am having a machine shop make me an accurate bushing so I don't have to worry about it..

Silicon Carbide (SiC) wheels (those are the gray ones) are generally the low cost wheels. Most aluminum oxide wheels are more expensive although the lowest cost white ones are in the same price range. Other than shedding huge amounts of grit, the low cost white ones are great.

A much lower cost approach than having a machine shop make precision bushings is to go to most any hardware store and get some Oilite bronze bearings. If necessary you can nest a couple of them to match the wheel hole ID to the shaft diameter.
 
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I use the Wolverine system with my 1725 rpm grinder and recently purchased a "green" wheel for a lot less money than the Norton SiC. While I don't think much of their plastic bushings and have had to order a replacement wheel at the mfg.'s expense, I am having a machine shop make me an accurate bushing so I don't have to worry about it. The finish achieved with this "green" wheel is nearly as good as honing, right off the wheel. For me, being old and lazy, it is well worth the $60+.
"Green" wheels are generally for tungsten carbide.

I recently installed a CBN wheel. I don't think I'll ever go back to a standard wheel again.
Me neither.
 

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I don't buy either of these arguments. I believe a sharper edge cuts better and lasts longer. My personal approach is to use a slow speed grinder to shape my turning tools and a Tormek to sharpen them. Unless there's a nick in the edge, I simply make a couple of passes on the 1,000 grit wheel, a pass or two on the leather honing wheel, and I'm back to turning -- with an edge that's far sharper than I could ever get from my high speed grinder. But, there are lots of very good turners who disagree strongly with my approach. They're just wrong, that's all. ;)

The last line gave me a chuckle! :D

There are many ways to get a good usable edge, and I'm no exception in that I've found my own way that works for me........

I'm also a believer in the sharper edge produces a cleaner cut. Gouges get honed with 600gt diamond hones and slipped with 600gt cone diamond.

Gouges and scrapers are ground with 80gt Norton SG wheels. Scrapers go directly to the work.

All tools are touched up frequently, because the sharpness of the edge starts dulling immediately. Once a method is developed that works well, constant practice makes the task less time consuming.......done in very quick order, actually......many times, it is done in seconds.

Gouges can be re-honed quite a few times before needing to return to the grinder. The secondary bevel created is the determining factor.

The main reason for using a slow speed grinder is less heat.....this is what destroys the temper, and edges last longer. ALWAYS keep a container of water close by........use it. Even when the temper is not altered, a cooler tool is much more comfortably used at the lathe.......and, this point is important to your turning, as well.......:)

ooc
 
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The main reason for using a slow speed grinder is less heat.....this is what destroys the temper, and edges last longer. ALWAYS keep a container of water close by........use it. Even when the temper is not altered, a cooler tool is much more comfortably used at the lathe.......and, this point is important to your turning, as well.......:)

ooc
Odie, the first part is right, less speed less heat (dependant on pressure applied) but you should never cool a HSS in water, they crack.

Maybe not now but eventually they will.
 

odie

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Odie, the first part is right, less speed less heat (dependant on pressure applied) but you should never cool a HSS in water, they crack.

Maybe not now but eventually they will.

Hello Ian.......

Never seen one crack in thirty years........ Perhaps it depends on how hot it gets, and this may be the result of constantly introducing excessive heat, which I don't believe is the case with my grinding techniques, wheel speeds, and wheel type that I use. I know for certain that higher speeds, and some types of wheels (usually the cheap ones, and in finer grits) are critical in minimizing the heat factor......but, individual technique is an equally important aspect of the sum total........

There have been times when I have inadvertently overheated, or at least, gotten a tool hotter than I'd have liked.......don't think very many of us can say it's never happened, but I suspect any cracking is due to consistently overheating a tool, and then quenching........

Since I've never seen that, I can't honestly say I can address what you are telling us, but there must be some reason why I've never seen any cracking after three decades of using water to cool a tool..........

edit: Thinking back, I almost certainly have ruined the temper at the thinnest portion of the tool, which would be close to the edge, and short lived because that portion will be ground away with successive returns to the grinder.........but, to ruin the temper over a large portion of the tool (I would think) would require some extreme excessive overheating situations. Since I've not seen what you are talking about personally, I can only theorize on the reasons why some turners might eventually cause a cracked HSS tool. Any further comments on this are certainly welcomed, but a cracked tool has not been, nor appears to be in the cards for me........for whatever the reason is.

ooc
 
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"Green" wheels are generally for tungsten carbide.
.

But, as fortune would have it, they do a splendid job on steel. The Camel brand at Woodworker's is an Israeli product, modestly priced and long lasting. Like CBN, the stuff is made, not natural, with the degree of quality control that implies. They do good work at the Kibbutz.

Once again, for those who might follow the herring, heat doesn't come from surface speed. Though you might press a bit harder to hold a tool against irregularities in a higher rpm wheel. Third law - equal but opposite.
 

odie

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This link may help Odie. http://www.practicalmachinist.com/vb/general-archive/grinding-hss-hot-89869/

I would say that you are not getting it hot enough to worry it.

Tis why I like my CBN's:D

Thanks for the link, Ian..........interesting read.


Yep, sounds like you would have to do some pretty aggressive grinding for the heat to be of concern......enough to see some redness in the steel. Mine never do get that hot, or anywhere near that hot. They do get hot enough to make it a comfort issue when I return directly to the lathe to resume work. Here, the tool is not really hot enough to prevent you from holding the steel with your bare hands, but it's much more comfortable to cool it down a bit.

Thanks for the "heads up" on this, because you did serve to inform me of the possible consequences of quenching a very hot tool. For 99 percent of my grinding, it's with very light pressure, and only to bring the cutting edge back into service. Total grinding time is something like 10 seconds for scrapers. Gouges take a little longer, but not by much. Here, it's done so carefully and delicately, that it might take a half a minute to do, but again, heat is not a factor.......

The hottest my tools get are when they are new, and initial grinding the profile shape.......so, there, some application of principle may exist that I will be aware of in the future.

thanks :D

ooc
 
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odie

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Once again, for those who might follow the herring, heat doesn't come from surface speed. Though you might press a bit harder to hold a tool against irregularities in a higher rpm wheel. Third law - equal but opposite.

Hello MM.......

Heat doesn't come from surface speed?

This hasn't been my finding.......and, this is exactly why the trend has been to slow speed grinders.

In the early 1980's, I initially used a standard 3450 rpm 6" grinder for sharpening lathe tools. When I purchased my current 1825 rpm 8" grinder, the difference in heat generation was very pronounced, and immediately noticeable. The 6" wheels, even though are spinning at 3450 rpm, have a surface speed that is much less than an 8" wheel spinning at the same speed.........I'm sure those who converted from 3450 rpm 8" wheels to 8" wheels at 1825 rpm will see a greater overall difference in reduced heat generation.

Heat is also a product of pressing harder, as you say........but, if you are pressing harder to conform to surface irregularities, then it's probably time to break out the diamond dresser and give your wheel a fresh dressed surface.

Some wheel compositions, are better than others for reduced heat generation, as well. I've got a stack of 6" and 8" wheels out in the shop that probably will never be used again.......but, it was when I first tried the Norton SG wheel, that I became hooked on it's performance. Being a "frangible" wheel, the surface continually breaks down, reducing the need to constantly re-dress. (SG wheels will require dressing from time to time, but the frequency is significantly reduced. Here, it's not the performance from clogged surface that requires redressing.......but, to true up the roundness of the wheel.) SG wheels are expensive........but, they last for years. I guess it all depends on what it's worth to you......:D


ooc
 
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Your opinions differ from measurable, repeatable science, but don't let that bother you unduly if you're happy. Just wanted to tell those who might be misled that they need not fear heat from a 3450, for example. It's coefficient of friction and pressure. Coefficient of friction is why the finer stone heats more, as does the duller (which is arguably finer, as well) grit. So if the grit fractures - CBN - or flies away - friable - revealing sharp surfaces that cut rather than rub - cooler. Not, once again, that it's a significant player with most modern alloys.

Ever notice how much faster the gouge warms when you "ride" the bevel? Even at the bottom of the bowl, where the velocity is nearly nothin'?
 
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sharpening

What happened to all the information on sharpening that was in the AAW article on sharpening by Allan Lacer? As I remember the photographs and analysis was very compelling not to go to tormek.

Ed
 

odie

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You're sitting in front of an entire reference library. Don't be lazy, seek it out. Here's one condensed, simplified version to get you started. http://www.codecogs.com/reference/engineering/mechanics/laws_of_friction.php

Not to open up a "can of worms", but MM might be bringing up something worth further discussion on this forum. The link in MM's post didn't mean much to me, because I have a difficult time applying a description that was intended to be read by those more "in tune" with the technical aspects than I am.......I need to absorb information of this type around an explanation targeted towards a layman's point of view, for it to be meaningful.



I did some online searching, and came upon this thread between several "machinists" on another forum that is intended for machine shop users:



click to view-----> http://www.practicalmachinist.com/vb/general/bench-grinders-1750-vs-3600-rpms-215968/



For those who are inclined to read that thread, you might be interested in what these people have to say.......and, the following post had my attention:



I'm going to be deliberately insulting:

1750 RPM bench grinders have been sold to gullible woodoworkers for several years now. They are hawked as the cure for over-heating cutting tools while grinding their edges. As grinders they work OK but not as efficiently as the "regular" speed grinders running at 3450 RPM. My complaint with these low speed grinders is they are sold to as a solution to a problem they do not solve.

The reason for the success of the newer slower speed grinders (1800 Vs 3600 RPM) is ignorance and pandering. The object of this wasteful purchase is ostensibly to prevent the overheating of edged tools when grinding them. The result is when purchased the problem recurrs as the original factory dress on the grinding wheel dulls.

Dispelling the ignorance:
The reason the tools overheat while being ground is friction. When the grinding wheel is clean and the abrasive grains in its surface are sharp, they cut cool and efficiently. Any edged tool dulls in use and that's as true with the abrasive grains in a grinding wheel as it is with a lathe tool or a plane iron. When the abrasive grains become dull from use they tend to rub not cut and ever-increasing force on the tool against the grinding wheel is necessary to sharpen it it. Thus a carbon steel tool overheats, turns blue and its temper is lost. A tool will overheat as readily on a 1800 RPM grinder as it will on a 3600 RPM grinder.

Solving the problem:
Learn to dress your grinding wheels. Dressing a grinding wheel "sharpens" it by knocking the dull grains out of the bond to expose fresh sharp grains. Incidentally dressing a grinding wheel removes the roughness, grooving, loading, and makes them round.

Make/buy a diamond wheel dresser on a hand shank so you can dress your grinding wheels. A suitable diamond dresser would be a small cluster diamond such as found in the the MSC catalog and the import tool catalogs for less than $40.

A suitable shank could be made from a piece of 7/8" round bar 12" long by drilling a 7/16" hole in the end 1" deep and cross drilling and tapping for a set screw. This is a life time tool when used in the home shop for the weekly grinding wheel tune up. Your grandchildren will pass it almost unscathed to their grandchildren and they will use it to dress their grinding wheels into the 22nd Century.

Exposing the pandering: when a perceived need is fulfilled by selling something useless by flattering the mark willingness to believe plausible nonsense, that is pandering: magnet therepy, herbal remedies for impotence, beauty products, and slow speed grinders are all in the same class of pandering.

When new, the slow speed grinders work great and why not? The wheels are fresh and sharp and they agressively cut while the work stays cool. You are pleased with the money spent for the problem is solved - until the wheels grow dull and then you're burning the edges again. Then you have to buy another grinder, don't you? Why not? Thats how you solved the first problem.

Nope. There's good reason why grinding wheels turn as fast as they do. That's the optimum speed established almost a hundred years ago for vitreous bonded aluminum oxide grinding wheels in professional shops. You'll never find a slow speed (half speed, actually) grinder in a professional sharpening shop. They're not productive.

Times haven't changed much since 1912. The abrasives and the bond and the process controls for making grinding wheels are much more refined today but the interaction of the grain with the steel edge is still the same 5000 to 5000 surface feet per minute is the optimum speed for aluminum oxide against hardened carbon or high speed steel.

You are looking for 5000 to 5500 peripheral feet per minute (FPM) for aluminum oxide against carbon and high speed steel. FPM = wheel diameter in feet times pi times the grinder RPM. Let's dissect this a little. A 6" wheel is just about perfect for a 3450 RPM grinder at 5419 FPM. 7" is a little fast but very usable. When a 7" wheel wears, it passes through the 6" optimum diameter. An 8" wheel is too large for a 3450 RPM grinder (getting up to the unsafe zone) and on a 1750 grinder is too slow. A 10" wheel is almost unsafe on a 3450 RPM grinder but a bit on the low side for 1750. 12" wheel is likely to burst on a 3450 RPM grinder but the peripheral speed is amlost perfect for 1750.

A grinding wheel wears away in normal use. Ideally, the grinder would have some means of varying the wheel RPM to mantain a constant peripheral speed. A variable or step pulley, a DC motor and variable speed control, a VFD and three phese motor are all suitable drives for those whose budgets or curiosity allow such exploration. There are in fact everal variable speed grinders now on the market but in the very cheap or the very expensive price brackets. A three phase Baldor #500 face wheel grinder equipped with a 3/4 HP VFD would seem to be the most plausible option but if purchased new would be quite expensive.

However single speed grinders have been around for generations and they work very well as is.

Exhortation:
The reason you may want to buy or make a slow wheel grinder is because of deliberately perpetuated ignorance and possibly because the other guys are getting them. Well, you're smarter now. Are you going to make/buy what you don't need and will work properly for a short time? Or are you going to learn dress your grinding wheels and solve the overheating problem forever?

No, you HAVE to use a diamond dresser to make a clean smooth round sharp grinding wheel for the precision grinding of fine edged tools. There are no low cost options. Trust me. The wheel dress obtained by use of Norbide sticks, star dressers, the abrasive stick are all a distant second best to the silky cool cut of a sharp well dressed wheel dressed not too smooth with a diamond dresser.



I have some further comments, as to how this applies to my experiences, but let's see if this stirs up any discussion on it's own merits.......

Boy.......this whole line of thinking really conflicts with what I've always thought about these things!..........but, my presence here is ultimately an avenue to a means for me to self improve........and, it's done exactly that, over and over again......:D

I'm sure I'm not the only one who wants to hear some additional input from a few of the other turners who post here.......so, give us your thoughts on this, if you would please.....

ooc




.
 
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john lucas

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Well that's very interesting. I have a grinder that lets me switch from low speed to high speed. I have done a lot of grinding at both speeds trying to learn the differences. I have a very light touch. I mean very light. It is much easier to heat the tool up with the high speed vs slow speed in my humble opinion. As best I can tell I use the same pressure. I can't tell that 3450 gives me any different edge than the slow speed.
It does take the grinder much less time to get up to speed, it's a lot less nerve wracking running at the slower speeds.
I won't get into the difference in sharp vs really sharp. I have tried an interesting experiment for the last year. When my tool doesn't cut as well I hone the inside of the flute with a fish hook diamond sharpening tool. It usually restores the edge without every touching the outside. After about 2 or 3 time I do have to go back to the grinder or hone the outside.
 

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Odie, I am sure that the person you quoted is fairly knowledgeable, but machinists have their own share of folklore and are hardly ones to point fingers at woodworkers.

His statement about grinder speed running at 3600 RPM (sync speed, not actual) as result of being optimized for aluminum oxide wheels nearly a century ago sounds like one of those bits of folklore. If anything, it is the other way around. He's also a bit early on his statement about electric motors. A century ago, most industrial machinery was still running on steam and IC engines. Most AC electric motors, especially early ones ran at 3600 (actually 3400 to 3500) RPM because they were two pole motors running on 60 Hz power.

He also completely missed the boat on why slow speed grinders are preferred to high speed grinders -- vibration. There are two reasons that vibration is less on low speed grinders. First, four pole motors have far less torque ripple and secondly, any imbalance in a grinding wheel will produce far greater vibration at the higher speed. Combine an unbalanced load with high torque ripple and you have a grinder that walks all over the place. Of course they can be balanced, but who does it?
 
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I will stick with a slow speed grinder. Most of the time we are just touching up the edge, which needs little pressure and fpm (feet per minute) speed. We only grind if we hit a rock. or the gouge/skew/scraper lands point first on the floor (do they ever land any other way), or if we want a different profile on the tool. Most of the time, this also requires little work, and the slow speed grinders will work fine, especially with the coarse wheels. Slow speed grinders are also much less intimidating than the high speed ones. I have had heat problems with dirty wheels, so I cleaned them many years ago. Never a problem with the CBN wheels. How hard you push into the wheel is part of the heat problem, along with how fast the wheel is spinning/fpm, and if the wheel is clean or not. All three contribute to heat build up.

I have never felt a gouge get hot from rubbing the bevel. Rubbing the bevel is supposed to be a feather light touch, not a burnishing rub. I have had gouges get hot from getting dull. They also will get hotter when they are cutting dry wood. I have blistered my fingers on a card scraper when using on flat work, mostly from pushing too hard.

robo hippy
 
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The key is in law 5. "When motion takes place, the direction of friction is opposite to the direction of relative motion and is independent of velocity. The magnitude of the force of friction is in a constant ratio to the Normal reaction, but this ratio may be slightly less than when the body is just on the point of moving."

Note that all the laws are from observation, not an explanation. Friction's a bit like gravity. It's there, we can measure it, predict and compensate for it, but we haven't any real explanation for it. The current interaction theory, where "non-rigidity" at the molecular level is assumed to be the source, has some problems. For one, we would assume that the greater number of interactions - larger surface - would give results consistent with smoother surface. Not so. The interaction theory comes from limiting friction. The body at rest is theoretically more interacted with the other.

Anyway, somebody will come up with a real reason some day. Until then, friction will be a constant in equations, just like the acceleration of gravity. No matter how fast things are moving.
 

odie

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If I'm understanding things correctly, then the friction is minimal, if one dresses his wheel often......and this may be a moot point if a good friable wheel is being used. It seems that the cutting surface of the bonded material within the wheel can dull, and it can clog with debris. Either one will cause an increase in the friction, resulting in increased heat. Both conditions can be minimized, and will result in less friction and heat with regular dressing.......or, in the case of a friable wheel, a new exposed surface.

When I first changed over from 6"/3450rmp to 8"/1825rpm, I was certain I had seen a major improvement in heat reduction. I'm not convinced that I didn't, but those who have variable speed grinders (like John Lucas) have a way to find out very easily, because all the variables are the same......only the speed is different. Someone here might easily experiment and give a "hands on" account of their findings.

It seems to me that if you hold a tool stationary on a grinder, you can overheat it fairly easy. None of us are doing that, because we rotate the tool on the grinding wheel along the entire length of the cutting surface. The slow speed grinder allows us to sharpen along that edge in a much slower, more deliberate, and delicately applied motion........which, to my thinking, is a very big advantage specific to the requirements of a lathe turner, over using a 3450rpm grinder.

I think MM has given us some additional insight.......but, the generic "scientific" laws he speaks of are probably not an absolute, when introducing other variables........such as wheel type, grinding methods, conditions and requirements specific to the lathe turner, and etc.

ooc
 
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I don’t think the rantings or someone on another forum has helped this conversation, maybe it’s just me.
I give this a try...
Heat is caused by Friction, which is increased by Pressure and Time. This entire issue of how to grind with as little heat as possible has been going on since the first tool was sharpened. We have since determined, heat is bad.

If you have two identical grinders, one 3600 rpm and one 1750 rpm and everything else is equal, the 1750 rpm unit will generate less heat during a normal turners grinding session.
Let’s say it takes me 3 seconds to roll my gouge from side to side and put a nice edge on it, regardless of grinder.
On the 1750 rpm grinder, (X feet) of grinding surface have passed by the tools edge in those three seconds of grinding. On the 3600 rpm grinder, (X x 2 feet) of grinding surface have passed by the tools edge in the same 3 seconds. So in the same time frame we effectively ground twice as much therefore generates more heat in the same amount of time. This is exactly what slow speed grinders were designed to address.

I will also mention, as Reed said, wood turners use their grinders primarily as a sharpening station, not in a traditional grinding role. In this refined role there is less need for rapid metal removal and more of a need to shape and contour, which usually takes more time, which equals more heat.

As far as cleaning is concerned, there is some truth to that, although it is not a substitute for slower speeds. When a wheel is in need of dressing, a few things happen. Since the wheel is clogged and is now smoother than usual it actually has a lower coefficient of friction at normal pressure, (you know, you start to grind and not much is happening) so you push harder increasing the pressure and coefficient of friction which generates more heat. Or you simply spend more time doing the same operation; more time generates more heat...

IMHO and in my shop, this is how it is.
 
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All of their stuff is intended for sharpening milling bits, so they have to be very accurate. A bit beyond what we need, but...... what does need have to do with it.

robo hippy
 
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I worked for years in a plant that threw away multiple diameters of aluminum oxide tubes (~325 grit). I have given these away at symposiums in Va, NC, Tn, Ga, and Fl for honing. They are wonderful for matching the inside of bowl gouges. I still get asked for more, after five years since I retired and lost my source. I have NEVER been told that "we don't want any, they don't work." My wife loves her Tormek. There are no sparks. Honing works. I hone after every trip to the grinder. :)
 
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What happened to all the information on sharpening that was in the AAW article on sharpening by Allan Lacer? As I remember the photographs and analysis was very compelling not to go to tormek.

Alan wrote several articles for the American Woodturner on sharpening and related topics. One of the articles he wrote with Jerry Wright discussed the sharpening of scrapers. Here's a quote from the conclusion of that article:
Simply polishing the top of the tools prior to raising a burr by grinding improves the resulting cut surface dramatically. This also may suggest that a finer grind might also improve burr quality. [Emphasis added. http://www.woodturninglearn.net/articles/newpdfs/Scrapers.pdf]
In the article, Alan used several different methods to sharpen a scraper and then compared those methods by turning an end grain poplar blank. All the methods started out with sharpening on a grinder using a 60 grit wheel. The best results were obtained by honing off the burr from the grinder and then raising a new burr with a diamond hone.

Note the speculation in the highlighted language from the conclusion: The authors seemed to believe they might have gotten even better results had they used a finer grinding wheel, like, say, a 180 grit CBN wheel or a 220 grit Tormek wheel.

An article in Woodturning compared results of dry and wet sharpening for skews and gouges. The author, Robbie Farrance, concluded tools sharpened with a wet grinder (Tormek) were sharper, produced a better surface, and lasted longer than tools sharpened with a dry grinder. http://www.tormek.com/en/leaflet/pdf/wet_or_dry_en.pdf

Note: I don't think the results reported in Woodturning had anything to do whether the process was wet or dry. Instead, I think it was the fineness of the wheel that mattered.

As you can see from the photographs in the linked articles, honing and/or using a finer wheel makes a big difference on how sharp an edge is produced.

 
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