T4 review, part 2, misconceptions and summary

[Ken S]

I have had a chance to use the T4 and T7 side by side.  I began this review with the notion that the T4 might be more of a lighter duty machine; that the smaller wheel and fifty per cent duty motors would be constraints; that the smaller machine would not cut as fast as the T7; and with questions about the mostly plastic housing.

These preconceptions have not stood up after use.  I have not found the "fifty percent duty" motor to be a realistic constraint. Even during several continuous comparative five minute grinding tests,  the top of the housing showed no signs of overheating. Eventually, the zinc housing did get somewhat warm, but not to an extent which was uncomfortable for my fingers or gave me concern. My hands tired long before the Tormek might have shown any signs of needing a rest.

I do notice a slight difference in the amount of hollow grind between the 200mm and 250mm grinding wheels. The difference is so slight that I would ignore it. Neither hollow grind is anywhere near what one would expect on a typical home 150mm (6") grinder. 

In direct grinding comparison tests, the T4 and T7 appeared to remove the same amount of metal in timed five minute tests.  The motor of the T7 is rated at 200 watts. The motor of the T4 is rated at 120 vatts. That stated, the surface feet per minute of the grinding wheels is quite similar. 

With the T7, the diameter of the wheel is 10 inches (250mm). Multiplying ten times pi, 3.14, we arrive at a circumference of 31.4. Multiplying the circumference by the speed of the shaft, 90 RPM (revolutions per minute), we arrive at 2826 surface inches per minute, or 235.5 surface feet per minute.

With the T4, the diameter of the wheel is 8 inches (200mm). Multiplying eight times pi, 3.14, we arrive at a circumference of 25.1. multiplying the circumference by the speed of the shaft, 120 RPM, we arrive at 3014 surfaces inches per minute, or 251 surface feet per minute.

These calculations are not to the nth degree, however they do show that the amount of grinding wheel presented to the tool is substantially equal between the T7 and the T4. This is in line with my test showing substantially equal amounts of the metal lathe turning bit being removed by the two machines in the five minute timed test. (The extra ten millimeters of width of the T7 wheel is noted, but would not factor in in most work.) This test and the surface feet per minute calculations indicate to me that there is no speed gain in the T7.

Some concerns were posted on the forum about the difference in the number of cubic inches or millimeteers between the 250mm and 200 mm wheels. This seems reasonable to me. However, should the wheel be worn to the point of needing replacement, the cost of a replacement 200mm wheel is just over half the cost of a 250mm wheel. And, the initial cost of the T4 is slightly less than the T7. In my opinion, these factors cancel each other.

There may be some concern about the lower part of the housing being plastic instead of steel. I have not found this to be a constraint in home use. Nor do I believe this would be a constraint in light commercial use. On a construction jobsite or a school situation, where everything should be "bulletproof", I would recommend the steel housing of the T7 for use in rough conditions.

The holes for the shaft and the support bar sleeves are milled into the zinc top of the housing. I have no concerns about their accuracy or durability.

For me, the real advantage of the T4 is its smaller size and weight. The T4 is approximately two thirds the size of the T7 and half the weight. It is definitely more  portable. I would note that the T4 is more easily carried when the grinding wheel is removed. The grinding wheel attached makes carrying the unit off balance. The shaft is the same diameter as the T7.  Being shorter, the shaft of the T4 would seem less prone to damage while being transported. I still believe that the best way to move any Tormek is with the grinding wheel removed. As all the T4s include the new EZYLock shaft, this is certainly easy and quick to do.

In summing up this part of the review, I hold with my original belief that the major consideration is choosing between a T7 and a T4 should be the work environment. In a school or factory environment, the T7 seems the logical choice, due to its steel housing. When the Tormek is in a large enough shop to have its own work station, the T7 might seem the better choice. In a smaller shop, where the Tormek may be frequently moved or space is limited, the T4 would be the logical choice.

I would also factor in the age and living conditions of the user. For a younger ambitious buyer with a large workshop and  big dreams, the T7 might be the choice. For a smaller shop or an older buyer who may be looking at the possibility of downsizing, the T4 would seem logical.

A third possibility, especially for current T7 or Supergrind owners, would be to have both. Let the larger unit continue to do its usual duties. For those who do sharpening at flea markets, sharpen their church's knives or bring their Tormeks to dinner at  friend's house, the T4 is just the ticket. It makes an ideal back up unit. All the jigs and almost all the attachments are fully interchangeable (the water troughs and universal support bars being excepted). This is one situation where the choice of marketing the T4 with no jigs makes sense.

When I purchased my first Tormek T7 in 2009, I was somewhat younger and had bigger dreams. If the T4 had been a choice then, I would have probably stayed with the T7. If I was purchasing my first Tormek today, the choice would be difficult. The only consolation is that there is no wrong choice. Both the T7 and the T4 are trooper Tormeks.

Ken

[Herman Trivilino]

I have had a chance to use the T4 and T7 side by side.

Very thorough review, Ken. Well done, too. We get folks wondering which which would be the better purchase for them, and I'm sure these reviews will be helpful for them in making their choice.

For those who do sharpening at flea markets, sharpen their church's knives or bring their Tormeks to dinner at  friend's house, the T4 is just the ticket.

I hadn't thought about bringing my Tormek to dinner. I suppose it would make me the hit of the party. 

[Ken S]

Thanks, Herman. What started this project were the posts where a prospective buyer was wanting a good comparison between the T7 and the T3 (and later the T4). I realized that most of the members who responded, although well intentioned, had never used a T3 or a T4. That well intentioned but not well informed group included me. That seemed like comparing two vehicles when one was the poster's work vehicle and the poster had only seen pictures of the other. I was unimpressed with the first online reviews. I wanted to see the T4 evaluated by a Tormek user.

I hope my series of reviews and responses will prove useful for both those who arethinking of purchasing a Tormek and those who are curious about "the little brother",

Ken