question on grinder speeds

Walker

get white wheels for the grinder - one at 80 grit and one at 120 - makes the grinder more versatile make sure your wheels are trued and run smoothly use a diamond tool to dress the wheel's face so it will cut and not burn the steel

did i firget anything? good luck and be safe

Ray

contradicts

When they say slow speed, I think that they are referring to really slow speed grinders, such as Tormek

Don't quench HSS

No, Oneway recommends a 3450 RPM grinder. They had a reason for it but I can't remember it. However, they quite properly recommend that the correct stone always be properly dressed which allows grinding to be done with less heat. Also professional turners want sharpening to be done quickly since time is money. I have a 1725 rpm grinder and will replace it with a regular

I don't understand how a useing a faster grinder will make grinding time any faster? Seems to me ginding time speed would depend on how fast you can move the gouge from one side to the other and if you can do it correctly in one shot or have to do it several times. Same thing with heat the longer you have to leave the tool on the stone the hotter it will get.

Bruce

In terms of speed of grinding, it really depends on how much you are trying to remove. If all you are doing is dressing the bevel to renew an edge, it really doesn't make much difference whether the speed is 1100,

When generating a new profile/geometry, of course faster is better because a (relatively) large amount of material is being removed. I have high speed six, low speed 8 and very low speed Tormek. If a lot of metal needs to be removed on a tool or for other grinding tasks, I usually prefer the high speed six, at least to get started.

As for HSS not being immune to overheating, take a look at the quotes from Latrobe steel (a major supplier)in my article on principles of sharpening that you can get a pdf of here:

Bruce Fergus> I don't understand how a useing a faster grinder will make grinding time any

# of pieces of grit in contact with the metal per second?

Faster speed = more cuts into the steel in the same time.

Considering the very low percentage of shop time spent with tools actually in contact with a grinding stone, the speed difference (in terms of time saved) is not worth considering. It is very much more a matter of the skill level of the practitioner To save more time, locate the grinder a few steps closer.

Mine lives about 1 step away at the left of the lathe headstock. (I don't use the outboard features yet).

I wasn't referring to time saved but that more metal is removed from the tool in the same time when the wheel is spinning faster than when it is spinning slower.

If that is not true, then why not use a staionary stone? It should be just as fast to sharpen a tool on a stationary stone as on a grinder, if I understand the argument being made... that the RPM of the grinding wheel is not relelvant to the speed at which one can sharpen a tool.

If there's no difference between 1725 and 3450, why would you expect a difference between 0 and 1725?

What yer saying depends on whether the tools are HSS. Personally I've not seen any Sorby M2 HSS gouges or chisels. So I'm assuming the original poster is talking about A2 turning tools which are not HSS. If you blue a A2 tool steel turning tool you will soften the edge. So what are the tools being used? I grind at about 300 rpm; at that speed you have to try to burn the tools. You are also much more in touch with whats happening at the wheel. I can feel and hear when the grind is right or not. I can also move much more slowly through what ever motion I need to get the perfect shape and bevel.

The key word is high speed steel. A2 is not HSS, M2 is and as far as I know Sorby doesn't offer M2 tools. Tempering temps for A2 range from 350 to 1000 degrees. M2 tempering temps are well above 1000 degrees; I think they are around 1700 degrees. So no you won't soften M2 but you will soften A2 at the edge. Straw-yellow color in tool steel occurs at 460 degrees, blue at

All temps are in Fahrenheit

How about this argument for a slow speed - lathe tools aren't the only things you'll grind on the beast. Think of your plane and shave irons, knives, carving tools, etc.

I think you've either misremembered or misunderstood something he said. Straw color is about 425F, blue is 600 for carbon steel. For other steel formulations the color vs temperature scale changes, but straw is always cooler than blue.

M2 is typically drawn at 1000F, which is a faint dull red glow, just barely visible in sunlight, so just getting it blue shouldn't have much effect on the temper.

-Jim Gott-

On 05 Sep 2004 00:31:56 GMT, snipped-for-privacy@aol.com (Jim Gott) wrote:

Why does OneWay recomend a 3450 grinder? I had a chance to pick the owner's brain once, and he had some interesting things to say about grinding that does contradict the "commonly held wisdom". First of all, he says:"the grinding wheels are designed to run at 3450 and will perform their best at that speed". Next I asked why people seem to think they get better performance at slower speeds (like 1725), and he said that unbalanced grinding wheels will vibrate a lot causing problems that are minimized by running at a slower speed. He also mentioned that not all grinding wheels are created equal, and not everyone dresses their wheels properly. Of course, good quality wheels, a balancing kit, and a "proper" dressing tool are made by OneWay! He also said that something that happens often with woodturners is that they have a mish-mash of different tools made from different steels. A wheel that grinds carbon steel well will not work as well with high speed steel and vice versa. And he recommends an 8" wheel over 6" because the hollow grind is not as severe. (I should have gotten into: isn't the surface speed different for a 6" and an 8" wheel? Does this mean that the 8" wheels are made differently to work their best at a higher speed? And what about when the wheel wears out?) Another question I had was: Is my cheapo grinder good enough, or should I buy a new Baldor or whatever? The answer was that if you balance the grinding wheels even the cheapest grinder will run smooth. So spend your money on wheels, not grinders. And balance them! And dress them whenever they get loaded up, properly!

Anyway, he seemed to have done a lot of research on grinding and wheels and stuff. So I bought a new OneWay wheel with balancing kits for my 25 year old El Cheapo brand grinder. The result: Very Smooth! The glitch: the balancing kits only work on wheels with 1" center holes, which seems to only be available on their wheels. The Norton SG wheels have a 5/8 hole or something so I couldn't make a side by side comparison with both being balanced. The balanced OneWay vs the unbalanced Norton: OneWay wins! Another glitch/weirdness: The OneWay wheels seem to be graded differently, or something. Their 80 grit acts like about a 100 grit Norton for grinding speed and finish. I've heard that the Norton SG is better, but is also more expensive. And I can't get them balanced like the OneWay.

Now as soon as I sell something I'm buying a new 8" grinder (El Cheapo, probably), OneWay wheels, more balancers, and maybe even the "proper" dressing attachment for my Wolverine.

Happy grinding to all!

CD boulder, co

I checked sorby's website and they don't mention their tools being made of M2 HSS. My guess is packard has it wrong

Hello John,

I found this under the FAQ from Sorby....

- There is a difference in the way Robert Sorby tools are hardened and tempered. The steels may be the same specification but are waranteed Sheffield High Speed Steel. The heat treatment process is vital to the performance of the tool. If the blade is not heat treated correctly the blade could shatter during use. If the heat treatment is incorrect then the cutting edge cannot be sharpened correctly, it will not hold an edge. In adjunct to this Robert Sorby gouges can be used to the full length of the flute, without loss of edge retention.

But it is very easy to tell HSS from carbon steel while grinding it. All my Sorby's seem to be HSS.

Best wishes, Dave

David Peebles Lyons, Ohio Revolutions Woodturning

I have both non-HSS and HSS steel tools. When I purchased my lathe, I also bought a non-HSS beginner set of tools. My plan was to buy the beginner set of tools and then over time buy better tools to replace the cheapies. I have recently just purchased a Sorby HSS 3/8" bowl gouge and Sorby HSS 3/4" roughing gouge.

Walker

Why can't you admit it? Go into any store or look in any catalog that sells Sorby turning tools and you will see "HSS" stamped on every gouge, skew, scraper that Sorby makes. If Sorby turning tools were not HSS they wouldn't be able to compete with all the other Manufacturers that are. As someone else said, it's easy to tell HSS from carbon steel by the way they look on the grinding wheel. HSS makes a light yellow spark, and carbon steel makes a darker, orange spark that breaks up and bounces all over the place. Trust me, Sorby turning tools are HSS.

-Jim Gott- San Jose, CA

You got it backwards. Bright yellow forky sparks for carbon steel and dull orange balls for HSS.

Peter Teubel Milford, MA