Tormek T7 problems

[angpanday]

I have a tormek T7 that I bought 2 years ago. I used this machine to sharpen long and thin kitchen knives. So far I find the results very good. Recently I started to get in the knife making hobby. For my first initial offering I made two models. A small knife with a 3 inch  Wharncliffe blade and a survival knife with a 5 inch drop point blade.  This two knives are made in D2 steel and has a 3/16 inch thickness. The angle I choose is 30-35 degrees since this two are both sporting knives. 

Now, one problem that I have noticed is at this angle the knife has a high risk of throwing back at the operator. It has happened so many times already that some times it will put a damage on the stone.  When this happen, I fix the wheel with a truing tool.  Is there a way to fix this problem? Am I push the blade to hard on the wheel?

[grepper]

Welcome to the forum!

What does the surface of your grindstone look like? 
Is it smooth and even? 
Are there any irregular, pitted or depressed areas on the wheel?

I had a bad grindstone that had areas that would grab a blade and pitch it back.  These areas had a different color than the rest of the wheel, and became quickly pitted even after dressing the grindstone. 

When a blade would hit those areas, it would grab the blade and pitch it back.  Very scary with a big, sharp knife!

Can you feel the stone grab the blade at different areas as it revolves?

Tormek, to their credit, replaced the grindstone with a new one and the problem went away.

That may or may not be what is happening for you.  I was not trying to sharpen @ 35 degrees.

One option is to sharpen horizontally with the rotation of the grindstone rather than vertically, into the grindstone.  That will probably resolve your problem, but there may or may not be some other issue happening. 

[Jan]

Welcome to the forum! 

I fully agree with Grepper, the reason of your issue is not clear, but sharpening away from the edge may resolve your problem. When sharpening high quality steel blade, like your D2, I always try to do it with little pressure.

The other thing I would like to mention is your blade thickness. The Tormek Knife jig works symmetrically for blade thicknesses from 2 to 3 mm (1/10" with some margin). For your blade thickness 3/16"= 4.8 mm you cannot expect that after turning the knife jig upside-down you will get exactly the same bevel angle as on the first side. You can correct it with the adjustable stop.

Good luck!
Jan

[angpanday]

It usually grabs the knife back when it hits the " A " portion of the blade . At the  " B " portion it is fine. This usually happen at 30 degrees up. The higher the degree the most likely it will grab 

[Magnus Sundqvist]

As mentioned above, use as little pressure as possible. If you increase it the risk of the knife digging into the stone is quite severe.
Have you done some experimenting on fitting the jig in the second position and turn the T-7 around so the stone rotates in the opposite direction?

Some times when I resharpen knives that has been broken in two and big amounts of steel needs to go I rotate the machine so I can apply a greater pressure and lower the risk of kickback from the knife.

[angpanday]

.
Have you done some experimenting on fitting the jig in the second position and turn the T-7 around so the stone rotates in the opposite direction?

Is it done on this position? How do I measure the angle?

[angpanday]

I saw this one sharpening on reverse...

https://www.youtube.com/watch?v=BKjMilG9LWY

[Jan]

Yes, the position is correct. The angle is set with the AngleMaster WM-200. It works for both grinding directions. 

Jan

[angpanday]

I will try it tomorrow and see how it works :-)

[Herman Trivilino]

Now, one problem that I have noticed is at this angle the knife has a high risk of throwing back at the operator.

Are you forgetting to halve the angle? For example, if you want a 40° edge angle on a typical knife you'll sharpen each side at a bevel angle of 20°.

[SharpenADullWitt]

Now, one problem that I have noticed is at this angle the knife has a high risk of throwing back at the operator.

Are you forgetting to halve the angle? For example, if you want a 40° edge angle on a typical knife you'll sharpen each side at a bevel angle of 20°.

I was wondering that and if you were lifting the handle or tilting the handle.
https://www.youtube.com/watch?v=fYURcwkKGPs

[angpanday]

I was wondering that and if you were lifting the handle or tilting the handle.
https://www.youtube.com/watch?v=fYURcwkKGPs

I just lift the handle.

Are you forgetting to halve the angle? For example, if you want a 40° edge angle on a typical knife you'll sharpen each side at a bevel angle of 20°.

Isn't it that you only half the angle on thin knives with a small bevel? My knife is 3/16 thick and the first bevel is wide....I don't divide the angle setting.

[angpanday]

https://www.youtube.com/watch?v=BKjMilG9LWY

I did the horizontal sharpening today and so far the result was okay. I was able to sharpen the knife at a 30 degree angle and the result was okay. ...It was razor sharp :-)

Is there any disadvantages when sharpening on the horizontal position?

[Ken S]

Angpanday

You raise a most interesting point. The Tormek handbook is probably one of the most comprehensive in the industry. That said, however, for all that is covered, much is either not covered or only sparsly covered.

The issue of grinding direction is mentioned in a general sense on page fifteen of the handbook. You have posted a link to the best source I know of for using the horizontal position with the wheel moving away from the knife edge, Steve Bottorff. Steve and I both live in Ohio (several hours apart). I have been most fortunate that Steve has taken me under his wing and taught me a lot about knife and scissor sharpening. Inspired by Steve, I generally use the horizontal position. I have not noticed a problem with grinding speed, and I like the feeling of having more control. In fact, a lighter touch with the horizontal position actually cuts faster with the SB-250 blackstone.

The handbook, in my opinion, seems to favor one method of working. It mentions the possibility of other methods. There may be a belief that showing one good method simplifies things for beginners.

I also suspect the vertical position evolving as the preferred method may have been influenced by the fact that it pointed away from the demonstrator and toward the audience. Unconsciously, this may have influenced the handbook author and video presenters.

I use the handbooks (I have several editions, including a very early edition.) for reference. I use these as working tools. I highlight, underline and make notes. They are no longer pristine collectors' items. I think my additions make them more useful, if not more valuable. I am grateful for all the good information in the handbook, and hope it will be expanded in future editions. The Tormek is continually evolving. Newer jigs have both improved its efficiency and increased its scope. The handbook and company videos have not kept pace with these innovations at this point.

Thanks for asking your question.

Ken

[angpanday]

Thanks Ken :-) I really like the tormek, It is the most versatile and well built sharpening system in the market today.  However, there are still a lot to be discovered to maximize its use  specially in sharpening knives.