Tormek T7 problems

[Jan]

Regardless of the method used, the shape of the blade, or the thickness of the blade, the bevel angle will be half the edge angle on any conventional knife that is sharpened on both sides.

Herman, considering a blade in Tormek knife jig, than your statement is correct, if the blade thickness is circa 2.5 mm.   

If the blade is thicker or thinner than 2.5 mm than the knife jig is not symmetrical with respect to upside-down flip. This results in asymmetrical bevels with slightly different bevel angles β1 and β2. The edge angle is the sum of β1 and β2, but in this situation we cannot say that the bevel angle is the half of the edge angle. 

The unpleasant think is, that bevels asymmetry is often visible at the first glance, as described by Wootz.  Fortunately Wootz suggested how to overcame this difficulty. 

Jan

[Herman Trivilino]

If the blade is thicker or thinner than 2.5 mm than the knife jig is not symmetrical with respect to upside-down flip. This results in asymmetrical bevels with slightly different bevel angles β1 and β2. The edge angle is the sum of β1 and β2, but in this situation we cannot say that the bevel angle is the half of the edge angle. 

I make no reference to the Tormek knife jig, Jan. If one is not careful, regardless of the jig or method used, it is possible to come up with unequal bevel angles. Some exotic knives are perhaps intended to be sharpened in this way. But a conventional knife has equal bevel angles on each side, and thus the bevel angle is half the edge angle.

When using any jig, measuring method, or sharpening tool, there are shortcomings to be overcome. Getting bevel angles equal on both sides of a knife using the Tormek knife jig is an example. Regardless, once you accomplish the task, the bevel angle is half the edge angle.

[Ken S]

I appreciate the fine work done by this forum to raise the standard of knife sharpening excellence. It is valuable and remarkable.

I would also like to point out that using standard issue Tormek equipmennt and methods will consistently produce excellent sharpness in a cost and time effective manner. A busy sharpener, while being aware of such advanced techniques, would not reasonably be expected to produce such sophisticated edges on a day to day basis at moderate prices. However, for those knife users and collectors who appreciate (and will pay for) the very best, the advanced techniques developed and advocated on this forum are sure to please.

Ken

[Jan]

I make no reference to the Tormek knife jig, Jan. If one is not careful, regardless of the jig or method used, it is possible to come up with unequal bevel angles. Some exotic knives are perhaps intended to be sharpened in this way. But a conventional knife has equal bevel angles on each side, and thus the bevel angle is half the edge angle.

When using any jig, measuring method, or sharpening tool, there are shortcomings to be overcome. Getting bevel angles equal on both sides of a knife using the Tormek knife jig is an example. Regardless, once you accomplish the task, the bevel angle is half the edge angle.

My laser goniometer measures the bevel angles with an accuracy better than 1° so I know how often the bevel angles are different, even with new blades. 

Even when sharpening a knife, which thickness is suitable for the Tormek knife jig, we can get unequal bevel angles. It is often in the case when we are grinding one side until burr forms but on the other side, where the burr appears quickly, we do not grind enough to get a symmetrical edge. Based on my experience it is more often when sharpening large edge angles (40°). 

To minimise the asymmetry I frequently flip the jig upside-down. In my understanding in this way less steel is removed to get a sharp edge.

Jan

P.S.: Dotted area in the picture A shows the steel removed in the when grinding one side until burr forms. Dotted area in the picture B shows the steel removed when flipping the jig frequently.

[Herman Trivilino]

Even when sharpening a knife, which thickness is suitable for the Tormek knife jig, we can get unequal bevel angles.

Of course we do. And even when the bevel angles are the same, that's no guarantee that the bevel width is the same on both sides because the edge is not always centered on the blade.

Regardless, if the bevel angles are equal, then the bevel angle is half the edge angle.

[Jan]

The attached sketch shows a blade with different bevel angles β1, β2.  The edge angle α = β1 + β2.

The half of the edge angle has no relevant meaning in this case. May be it was the desired bevel angle.

Example: If β1 = 24°and β1 = 16° then α = β1 + β2 = 24° + 16° = 40° and α/2 = 20°.

Jan