I am looking for a stone to replace my badly chipped SG200. Mine cannot be saved. Contact me off list and we can work something out. I'm im Ohio.
Contact Steve Bottorff. His web site is SharpeningMadeEasy.com. Steve lives in Northern Ohio and may be able to hook you up.
I think this is an excellent idea. A 250mm wheel worn to 200 mm has used its best days with a larger Tormek, but is just coming into its own with a T4.
Ken
How does it fit? It is 2" and the 200 is 1.5".
Quote from: Nosetotail on July 27, 2020, 02:54:33 AM
How does it fit? It is 2" and the 200 is 1.5".
I didn't think it would fit,,, but it does without any issues.
https://forum.tormek.com/index.php?topic=3344.msg20259#msg20259
The side indent of the 250mm wheel is greater than the side indent of the 200 mm wheel. Between the indent difference and a little extra length of the threads on the shaft, either size wheel can be mounted on any of the Tormek models.
Ken
Here are some details: http://sharpeninghandbook.info/Grindstones-StoneLife.html (http://sharpeninghandbook.info/Grindstones-StoneLife.html)
Kind regards,
Rich
Rich,
Your Sharpening Handbook is a valuable resource for us. And, your entry about Tormek wheels is useful, as far as it goes. However, I believe it leaves out some key information.
I became aware of the interchangeability of 200 mm and 250 mm grinding wheels when I first purchased my BBN wheels from D-Way. All of the D-Way CBN wheels in all sizes share a common bore diameter of one inch. D-Way manufactures several nicely machined steel reducing bushings. This allows one wheel to be used with grinders with different bores.
I was surprised to see that the same steel reducing bushing worked with both diameters of Tormek wheels. With your dimensions, it would be useful to note that sizes of Tormek models have shafts which share a common length of shaft for the section which holds the grinding wheel and the same thread length. The thread length is long enough to compensate for the slight difference in thickness between the two wheel sizes.
The majority of the difference is absorbed by the difference in the inset of the one side of the wheel. This can be problematic with non Tormek wheels with the recess; the shaft is not long enough to thread well with non standard wheels.
I disagree with trying to use up the last millimeter of wheel size. This is not just my opinion. In this video, Tormek expert, Terry Beach, discusses why he only uses his wheels down to 220mm. (last minute of the video) Here is the link:
https://youtu.be/8zQDmQ_n7wg
Personally, I would not want to pay for a knife sharpening with so much hollow in the grind.
Ken
Quote from: Ken S on July 28, 2020, 03:48:55 PM
...
I disagree with trying to use up the last millimeter of wheel size. This is not just my opinion. In this video, Tormek expert, Terry Beach, discusses why he only uses his wheels down to 220mm. (last minute of the video) Here is the link:
https://youtu.be/8zQDmQ_n7wg
Personally, I would not want to pay for a knife sharpening with so much hollow in the grind.
Ken
He actually says down to 200mm (at 7:40).
Considering a T-4 wheel starts at 200mm... it seems a bit of a conflict? I think on chisels etc. with wider bevels it might matter... but on knives, the hollow is pretty slight, IMO. Lately, I've been using the Tormek (T-4 at around 198mm) to just set the bevel, finishing them on bench stones, and if I use a coarse stone, I'll see scratches across the entire bevel under magnification, after just a little sharpening. (By comparison, with a fine stone, they're mainly at the top and bottom of the bevel). So the hollow is there, but I'm not sure how to practically test to see an actual influence?... although I'm pretty happy with the results at this point... if anything, my theory is, the hollow just behind the bevel could improve performance... (but haven't made any actual direct comparison or testing).
CB,
You are correct about the 200mm. (Oops......)
I have thought about combining the 250 and 200 mm wheels during sharpening. I have not formulated any conclusions. I'm basically a chisel sharpener.
Ken
When I sharpen on grindstones that are 180-200 mm on my T-2000, I use them on turning tools, both wood turning and metal, and on my pocket knives. I find that the small amount of concavity in the grind is not a real issue. What is more of an issue is not sharpening often enough.
Rich
Bump. I'm still looking for a tired SG250 if anyone is willing to sell.
John
John,
Ping me in about 5 yrs. Retiring in 3.5, so should have my new one used up by then.
Kind regards,
Rich
Rich,
I think we live close to each other. Do you only sharpen woodworking tools? I am learning knife sharpening. My latest quest is to learn serrated knives. If you have tons of experience how might I arrange a lesson from you?
John
I have acquired a SG200 wheel. I am no longer in need if a wheel for my T4.
Thank you,
John
We had a long discussion about this same thing years ago as I was poopooing the use of the T3 now the T4. One of my arguments being that the stone on the then T3 was already used up. The first moderator of the forum and importer of the Tormek system, Jeff Farris said on the forum that he retired stones at 200mm. Yet the T3 is born that way. Turns out the limiting factor was the ability of the T7/T8 nee Supergrind stone to reach the water trough. At 200mm it was about at its limit to remain wet. No one was actually concerned with the concavity caused by the smaller stone. But as noted above there is an increase in hollow ness. Is that a word? Once again, it was I that expressed concern about this as I considered it a serious weakening of the edge due to less meat behind the edge because of the greater hollowness. I was pretty much poopooed away yet again on my thinking. I am still of the opinion that a flat grind is the best grind for a knife blade or any other blade.
Quote from: jeffs55 on October 17, 2020, 12:57:25 AM
We had a long discussion about this same thing years ago as I was poopooing the use of the T3 now the T4. One of my arguments being that the stone on the then T3 was already used up. The first moderator of the forum and importer of the Tormek system, Jeff Farris said on the forum that he retired stones at 200mm. Yet the T3 is born that way. Turns out the limiting factor was the ability of the T7/T8 nee Supergrind stone to reach the water trough. At 200mm it was about at its limit to remain wet. No one was actually concerned with the concavity caused by the smaller stone. But as noted above there is an increase in hollow ness. Is that a word? Once again, it was I that expressed concern about this as I considered it a serious weakening of the edge due to less meat behind the edge because of the greater hollowness. I was pretty much poopooed away yet again on my thinking. I am still of the opinion that a flat grind is the best grind for a knife blade or any other blade.
I'm guessing this is the thread you're referring to?
https://forum.tormek.com/index.php?topic=2413.0
Jan's pictures are gone, but I think it's the same ones in this thread...
https://forum.tormek.com/index.php?topic=3428
At any rate, it would seem to me that it would be easy enough to test... (maybe?) ???
But, I don't think one is "best"... depends on what you're doing.
Lately, I've been doing the main grind on a T-4 (EDC knives mostly)... then finishing on a diamond stone (just enough to clean up the edge). Not sure if it's best... but it's working well for me! :)
What do we know? And, what do we not know? We know that an SG-250 worn to 200mm will fit on the T4, including the water trough.
In fact, a 250mm full size SG-250, or any 250mm Tormek grinding wheel, will fit if the water trough is removed. I know this for two reasons: I swapped wheels, and, I measured the part of the shafts which hold the grinding wheel on my T8 and T4. Both models measured identically. Although the 250mm wheels have a 50mm thickness and the 200mm wheels are 40mm thick, the 250mm wheels are indented more, making them interchangeable.
What do don't know, or at least I don't know, is if the extra weight of the thicker wheel would overtax the lower wattage motor of the T4.
Jeff, at the risk of sounding like an Originalist, when Jeff Farris made that statement, "the Tormek" in the US (where Jeff Farris was the Tormek agent and demonstrator) was the 250mm Super Grind 2000 or T7. In my 2009 handbook, the SuperGrind 1200 was not available in 120volt 60 Hz for US use. I believe he was thinking only in terms of the 250mm models. (Incidentally, the water trough on the T8 is designed to function with smaller wheels.)
We disagree as friends.
John,
I think you are probably better off with your replacement SG-200. That's more of a gut feeling than a well reasoned, documented position.
Ken
I'm guessing this is the thread you're referring to?
https://forum.tormek.com/index.php?topic=2413.0
Bingo.
jeffs55:
If "hollowness" doesn't ring true, try concavity.
AFAIK, the only merit of a hollow ground bevel on, say, a chisel or plane iron is that hand whetting becomes easier.
Ice skate blades are probably another matter.
In 1972, I bought a garden variety dry grinder for the time, a six inch, 3450 RPM Sears Craftsman. Most of us were using six inch grinders back then. Many of us were still using oilstones. Flat grind sharpening would have been a very labor intensive project. Two contact point hollow grinding made a lot of sense. Yes, Ega, as you note, the advantage of hollow grinding was in labor saving.
I can spot a hollow ground blade from a six inch grinder. I have difficulty seeing the difference between blades ground with a T4 and a T8, even using a straightedge. I have compared chisels sharpened with both sizes. In my opinion, with either a 200mm or a 250mm diameter grinding wheel, the hollow ground effect is more theoretical than practical.
Ken
Quote from: John S on October 17, 2020, 12:13:02 AM
I have acquired a SG200 wheel. I am no longer in need if a wheel for my T4.
Thank you,
John
I have a 200mm SB silicone blackstone wheel for sale, but I never contacted you as I'm in Canada, and shipping across the border is just crazy right now. I just received a 12 lb (5 kg) shipment from a US sharpening supplies dealer. The expedited shipping (by air) was $90 CAD and it still took 14 days.
I have had several small orders recently shipped from overseas. Shipping costs are crazy. I think the prudent thing now is to hold off if possible.
Ken
Hello,
why guess what is difference between flat and hollow grind on different wheel diameters when calculation is available nearly one year? :o I thought that it is resolved...
Differences for small thicknesses of blades (typically ca. 1 mm at the edge heel) are negligible, for thicker blades (eg. chisels) there are higher deviations but I didn't observe any difference between flat and hollow grind in real life.
For me, there is only limitation for Scandi grind which should be flat according to purists. Practically I didn't see/feel difference between flat grind and grind made on T-8 eg. on carving knife Morakniv 106.
Example below is double bevel grind with blade thickness 10 mm (= single bevel grind with blade thickness 5 mm), grinding angle 25°, wheels dia 200 mm and 250 mm.
jvh
$90 CAD
What's that, about $15 USD? LOL
It was $67.22 USD.
BeSharp, Thank you for the thoughts.
I wonder why shipping costs has skyrocketed? Can't be fuel prices. I have to assume opportunistic price gouging. Freight Boats and planes cost the same to sail and fly.
John
That's what it costs for US Postal Service Expedited Air to Canada. Apparently many retailers are refusing to ship by ground as it will be even slower due to the increased volume. Many Canadians, including myself, used to pop across the border to pick up as many American retailers offer free US shipping. Due to COVID, we can't do that anymore.
I am also in the market for a Japanese Waterstone, if anyone has another SG250 that is worn down to 200mm, please contact me: jasonstone20@yahoo.com