Author Topic: T4 vs T8 grid hollownes  (Read 8941 times)

Offline troflog

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T4 vs T8 grid hollownes
« on: July 09, 2018, 11:21:51 pm »
Hello
I am planning to buy a Tormek, but can decide betweeen T-4 and T-8. The maxium 30 min sharpening time with the T-4 is okay, but I am more worried about the hollowness. Since it have a 200 mm stone, it will be more hollow than the 250 mm T-8 stone. How much worse will the t-4 egde be compared with the T-8 egde. I have used japanese water stone for 5 years but an illness in my hand keep me from using them any more.

Offline Grizz

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Re: T4 vs T8 grid hollownes
« Reply #1 on: July 09, 2018, 11:25:35 pm »
I chose the T-8. its a little larger and has an unlimited run time without a cooling down period. better motor in my opinion.

Offline Ken S

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Re: T4 vs T8 grid hollownes
« Reply #2 on: July 10, 2018, 02:01:17 am »
Welcome to the forum, Troflog.

I use both sizes of the Tormek. Theoretically, the T4 200mm grinding wheel will produce a slightly larger hollow grind than the T8 250mm grinding wheel. I have compared identical chisels ground with the two sizes, and find it very difficult to detect any difference. Frankly, the hollow grind debate goes back a long time to the days when home shops generally had 150mm (6”) high speed dry grinders. With a 150 mm grinding wheel, especially when worn, there is a definite hollow grind. For me, between the T4 and T8, the difference in hollow grind is a non issue.

Another non issue is the "fifty percent duty” limitation of the T4. This was a real problem in the T3 with its all plastic housing. The plastic housing prevented the heat from escaping, causing the plastic surrounding the shaft to melt. The overheating problem was due to the housing not the motor.

Tormek corrected this problem with the T4. The T4 housing incorporated a cast and machined zinc top. Instead of holding the heat, the zinc top acts like a radiator. The usb sleeves and motor shaft openings are machined into the zinc top, increasing the accuracy by 300% according to Tormek. Incidentally, Tormek uses the identical housing design in the T8.

As far as needing a rest, you and I will need to stop long before the T4.

Do not choose the T4 to save money. When you add in the necessary TT-50 Truing Tool and SE-77 Square Edge jig, the difference in price is minimal. The grinding wheel for the T8 lasts longer due to its size. A replacement wheel for the T4 costs less. I would call it a draw. I would not be concerned about the SB blackstone not being available for the T4; the DWC-200 coarse diamond wheel (originally made for the T2, but fully compatable used dry with the T4) is a more useful wheel than the SB.

Fortunately, there is no bad choice. Either the T4 or the T8 is an excellent Tormek. The T4 is more compact and portable. The T8 now has abrasive on one side of the diamond wheels. (a nice feature, however, we used Tormeks without this feature for forty years). We taped magnets to our water troughs until 2010, and this simple fix still works.

Please keep posting your questions. Purchasing a Tormek is an investment. Ask plenty of questions.

Ken

Offline troflog

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Re: T4 vs T8 grid hollownes
« Reply #3 on: July 10, 2018, 09:18:12 am »
I have another issue. I have to store my Tormek in a non-isolated shed during winter. I live in Norway so the winters can be cold (-10-15 C). If I need to use the Tormek I plan to take it inside for 24 hours before I use it (in order to remove any moisture). Will this work?

Offline Ken S

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Re: T4 vs T8 grid hollownes
« Reply #4 on: July 10, 2018, 02:19:05 pm »
Troflog,

Stig's territory assignments with Tormek have included Norway, Finland, and Canada. I am certain he has encountered many unheated shed situations and could offer expert advice.

You are probably familiar with the Scandivavian custom of long summer holidays. (I wish we had them in the US!) Stig is presently on holiday until mid August. I would ask that you hold your question until mid August. I don't think you will have any freezing problem until then, even in Norway... :)

Ken

Offline cbwx34

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Re: T4 vs T8 grid hollownes
« Reply #5 on: July 10, 2018, 02:50:30 pm »
I have another issue. I have to store my Tormek in a non-isolated shed during winter. I live in Norway so the winters can be cold (-10-15 C). If I need to use the Tormek I plan to take it inside for 24 hours before I use it (in order to remove any moisture). Will this work?

From my understanding, the biggest concern is storing the wheel with water, which could potentially freeze and crack the wheel.  One forum member tested it by freezing his wheel in a block of ice, with no ill effects... you can read it HERE.  Not really recommended, but it survived.  So, I would think letting it warm up a bit before use, and also letting the stone dry a bit before storage should be OK?

As for the "hollow grind" issue, as Ken said, no big deal... especially if you're sharpening knives (I'm guessing since that's the topic area you posted in)... not a concern in that small of a width distance, IMO.  (HERE'S an interesting thread on the subject).
« Last Edit: July 10, 2018, 03:10:28 pm by cbwx34 »

Offline Ken S

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Re: T4 vs T8 grid hollownes
« Reply #6 on: July 10, 2018, 04:37:37 pm »
My very low tech solution would be to to dismount the grinding wheel and bring it with me when I left the cold shed. Store just the grinding wheel warm and dry between sharpening sessions.

The late Leonard Lee, founder of Lee Valley and Veritas, wrote an excellent sharpening book. He grew up on a farm in Western Canada and was no stranger to axes and Canadian winters. He describes a firewood gathering trip where his uncle, a careless man, had an exceptionally nice axe. Good practice was to sleep with your axe, to keep it warm and less brittle. His uncle neglected to do this, and the brittle axe head broke the next day..

Ken

Offline troflog

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Re: T4 vs T8 grid hollownes
« Reply #7 on: July 14, 2018, 10:47:20 am »
Thank for the good answers.I have almost decided to buy the T-4 since it is it is 250 $ cheaper in Norway even with all the jigs I nerd
1.So the t-4 will not get on fire if I use it for 35 minutes?
2.I have read somewhere that it is cheaper to sharpen on the t-8 due to more sharpening stone for the money. Is that true?
3.The T-4 stone is 200 mm. How much can I wear it down before the hollowness becomes a problem?
« Last Edit: July 14, 2018, 11:33:58 am by troflog »

Offline Ken S

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Re: T4 vs T8 grid hollownes
« Reply #8 on: July 14, 2018, 01:15:55 pm »
You are asking good questions, Troflog.

No, the T4 will not catch on fire. The overheating problem was only on the T3. The all plastic housing on the T3 could overheat with continuous use because the plastic did not allow the heat of the motor to dissapate. The plastic could melt enough to cause the opening for the shaft and bushing to shift, causing misalignmemt. Tormek corrected this situation with the T4. The T4 housing has a precision machined zinc top. The top has the precision machined opening for the shaft and bushings, as well as the sleeves for the universal support. The zinc top acts like a radiator and dissapates the heat. Incidentally, Tormek later used this same zinc top design with the T8.

When the T4 was first introduced, I met a representative of Tormek and a representative of the US importer. I asked them pointedly about the overheating issue. What would Tormek do if the motor of my T4 burned out just short of the end of the seven year warranty? Tormek would send me a shipping label at their expense and make my Tormek like new, except for grinding wheel wear. No question about thirty minute use. Technically, the T4 motor is not listed for continuous duty. In reality, you will tire long before the T4.

The 200 mm grinding wheel should be replaced after wearing down to approximately 150mm. The 250mm T8 wheel will last longer, however, it also costs 40% more. In my opinion the cost to useful life balances out. This will continue to be less of an issue with the advent of diamond and CBN wheels. Incidentally, the slightly higher RPM motor of the T4 balances out with the smaller when calculating the Surface Feet (or meters) per Minute, the actual cutting rate.

When comparing cost, you must add in the cost of the TT-50 truing tool with the T4 plus the cost of the SE-77 if you sharpen woodworking chisels and plane blades.

In my opinion, I would disregard cost difference in making your decision. Between the T4 and T8, there is no bad choice. You will not wish you had bought the larger model if you choose the T4. For me, the main difference is portability. If you never move your Tormek, either will work well. If you move it a lot, the T4 has about half the weight and is more comfortable to carry.

Keep asking questions. A Tormek is a lifetime purchase.

Ken

Offline cbwx34

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Re: T4 vs T8 grid hollownes
« Reply #9 on: July 14, 2018, 06:00:47 pm »
I would add, how much sharpening do you plan on doing?  Most "home sharpeners"... maintaining a few tools, kitchen knives, a pocket/hunting knife or two should find the T-4 up to the task, and the stone would last years.  But if you have a job/hobby that requires a lot of sharpening, or plan on sharpening for others... I'd look at the T-8.

Also, the "psychological factor" comes into play... if you get a T-4 and spend all the time wishing you'd got a T-8... might as well save up... in the long run, you'll be happier, even if the T-4 would have worked. ;)
« Last Edit: July 14, 2018, 06:15:38 pm by cbwx34 »

Offline AKMike

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Re: T4 vs T8 grid hollownes
« Reply #10 on: July 14, 2018, 09:09:04 pm »
The 200 mm grinding wheel should be replaced after wearing down to approximately 150mm. The 250mm T8 wheel will last longer, however, it also costs 40% more. In my opinion the cost to useful life balances out. This will continue to be less of an issue with the advent of diamond and CBN wheels. Incidentally, the slightly higher RPM motor of the T4 balances out with the smaller when calculating the Surface Feet (or meters) per Minute, the actual cutting rate.

Ken

If I've done my math right, there's 72% more usable stone with the 250mm wheels (250mm down to 180mm)  compared to the 200mm wheels (200mm down to 150mm), so if they only cost 40% more, they are a comparative bargain.

Mike

Offline Ken S

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Re: T4 vs T8 grid hollownes
« Reply #11 on: July 15, 2018, 01:26:09 am »
CB,

Your appraisal of the T4 seems rather caustic to me. Are you basing it on actual hands on experience?

My experience with my T4 has been positive. Also, I do not recall any forum posts from dissatisfied T4 owners who wished they had purchased the T7 or T8. I don't know which would be a better choice for Troflog. That is his decision. We do not know how much or what kind of sharpening he intends to do. If he intends to do heavy duty high production sharpening, the T8 would seem the logical choice. I would not limit the T4 to only occasional "home workshop" sharpening.

Mike, I am sure your math is more accurate than mine. I don't think of cost difference when comparing Tormek models. I would prefer they were priced the same, equipped with the same accessories. Then the decision would be based solely on which model fit the buyer's needs.

Ken

Offline cbwx34

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Re: T4 vs T8 grid hollownes
« Reply #12 on: July 15, 2018, 05:20:53 am »
CB,

Your appraisal of the T4 seems rather caustic to me. Are you basing it on actual hands on experience?

My experience with my T4 has been positive. Also, I do not recall any forum posts from dissatisfied T4 owners who wished they had purchased the T7 or T8. I don't know which would be a better choice for Troflog. That is his decision. We do not know how much or what kind of sharpening he intends to do. If he intends to do heavy duty high production sharpening, the T8 would seem the logical choice. I would not limit the T4 to only occasional "home workshop" sharpening.
...
Ken

I have no reply... as I see nothing "caustic" about it.

 :-\

Offline Ken S

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Re: T4 vs T8 grid hollownes
« Reply #13 on: July 16, 2018, 01:00:52 am »
CB,

I owe you an apology. My choice of the word "caustic" was not well chosen. I did not mean to offend you.

Your comments reminded my of the early forum comments about the T4, which were made before you became a member. These comments were quite negative, even though the posters had never used or even seen a T4. I wrote my review of the T4 to include a balanced report based on actual use.

I do not mean to imply that the T8 would be a bad choice for Troflog. We do not even know his intended use or volume of sharpening. It would help if you posted that, Troflog.

Ken

Offline troflog

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Re: T4 vs T8 grid hollownes
« Reply #14 on: July 16, 2018, 11:35:49 am »
Hello Ken
I am going to use the Tormek for sharpening my own knives,garden tools, scissors and axes. I also sharpen some of my friends knives (but not so often as my own knives). I think I will go for the T4 since I do not have a perment spot for the machine. I live in a small house with only an outdoor unisolated shed where I have to store the machine. So I have to bring the machine inside my house if I want to sharp during winter.
The most important for me is that I am able to get as sharpe egdes as with the T8


Does anybody know if the t4 will get a diamond stone in the future.
« Last Edit: July 16, 2018, 06:11:00 pm by troflog »