Grinding wheel surface issues - Resolved

[grepper]

I am a happy T-7 owner.  One issue I have noticed is that the surface of the standard grinding wheel quickly develops rough spots that have more friction than the rest of the wheel.  It's as if the entire wheel is glazed, with areas where the glaze has broken through.  (The wheel is not glazed, it cuts fine, I'm just using that for illustration.)

Using the stone grader I can feel it grab each time one of these areas passes beneath it.  When sharpening blades, it jerks the knife with each pass.  Grading helps, but does not totally remove the problem areas as they very quickly redevelop.  Resurfacing the wheel removes them for a shot while.

Is this just normal, or could I possibly have a funky wheel?

Thanks!

[Justin]

Are you using the stone grader in the same way and for the same time as the tutorial?

http://www.youtube.com/watch?v=eYNkEKS5-KY

[grepper]

Yes.  Sort of.    I'm not doing the sliding back/forth sideways because I found that it tends to round the edged of the stone where it makes with the wheel.  In the long run this seemed to cause rounding of the edges of the grinding wheel.  I saw some post here by Jeff saying to avoid this.

The stone does resurface the wheel.  It's not that some area of the wheel surface is not getting touched by the stone.

Thanks for the reply!

[Jeff Farris]

Grepper,

I've seen that (rarely) before. It most likely is a small inconsistency in the grindstone composition. It will go away after a bit more use. They are usually less than 1mm thick.

[grepper]

Thank you for the reply Jeff.

The problem has been happening since the unit was new.  I've removed at least 3mm of the wheel already with the truing attachment.  The areas vary in length from just spots to 3 cm to 4 cm long, and and up to 1 cm wide.  It's like the surface of the stone "breaks" in patches, exposing unconditioned grindstone just under the surface.  It looks almost like a thin layer of paint has chipped off a surface.

Is there anyway to attach an image file?  It's obvious when you see a photo of it.

Thanks,  Mark

[Jeff Farris]

Mark,

What country are you in? I would contact customer support in that country. Mark the spot with a waterproof marker and see if it is happening in the same spot on the stone each time.

[grepper]

Thanks Jeff,

MI, USA.  That's a good idea Jeff, as I'm not sure if it's the same places all of the time.

I'm glad to know that it's not normal, and that maybe customer service may address the problem.  It makes careful sharpening difficult when the wheel grabs at the blade each time around.

Thanks again for your assistance Jeff!

Mark

[grepper]

Here is a picture of one of the breaks in the grinding wheel surface.  These breaks are very "sticky" and will actually jerk on the stone grader or a blade during sharpening.

http://tinyurl.com/b2md6x5

[RJM]

My (T-7) has always done the same as yours. The grabbing is so violent at time that the wheel grabs snatches the grader right out of my hand. There have been a couple of time when the entire T-7 jumped right off of the cart that it sits on.

RJM

[grepper]

RJM,

Thank you for your post!  Very useful to know I'm not the only one with this issue.

It's amazing how "sticky" and dangerous these surface aberrations are! 

One time I was sharpening a large kitchen knife to about 20 degrees.  One of these spots grabbed the blade and, yanking the jig from my hands, pitched the whole thing under the control bar. It was sudden and freightening.

I threw my hands in the air and jumped back from the machine to avoid having the now razor sharp pointy knife impale my foot as it bounced off the bench and fell to the floor. 

As my heartbeat returned to normal, my first thoght was that I might have suffered a serious  wound, but luckily I was undamaged and had not sprung any leaks!

This incident has now made me feel somewhat afraid and intimidated by the machine.  This feeling, in itself, is not necessarily a bad thing around any power equipment as it is a reminder to be attentive and careful, never getting sloppy and taking the environment and equipment for granted.  I am now considering chainmail butchers gloves and steel tipped boots.

These stone surface issues are obviously a safety concern.

[mski2]

WOW are you running at 150 RPM ?
You would figure that a $300 wheel would have NO issues

[Rob]

Sounds like the binder holding the ceramic particles has failed to mix properly in the manufacturing process. It seems to have left weak spots that break up with use. It's like the glue hasn't "taken" properly but not uniformly across the stone.

Jeff's advice of taking it to local dealer support sounds right. Aren't Tormeks guaranteed for 7 years?

[grepper]

The machine is not modified, and I seem to remember 150 rpm is its rated speed.  So yes, I assume so.

150 rpm seems relatively slow in comparison to some other drilling equipment like a 30K rpm Dremel, but you have to consider, if math serves me correctly, (I could be wrong), that would still be 2.5 rpm / second.  A 10" wheel would be about 30" of wheel surface per revolution, or about 75" or 6.2 wheel surface/feet per second.  (Hey math people, please correct me if I'm wrong).

Add to that the fact that the T-7 is a  beautiful, powerful grinder.  I imagine it would take a lot to bog it down, let alone jam it to a stop.  So, yes.  If you jam something against the wheel surface and utilize the control bar as a fulcrum, from my experience it has considerable torque, and "things" can happen surprisingly quickly.

Does anything in life come with no issues?  Even $300 things? 

Apparently RJM's and my experiences are not the norm.  Hopefully Tormek will address the problem.

[grepper]

So, I contacted Sharpening Supplies, the company where I purchased the machine, (great company to deal with BTW), and they directed me to Affinity Tool Works who is apparently the company handling US Tormek warranty issues.

Affinity was very friendly and helpful and told me that there would probably be no problem in getting a replacement wheel, saying that Tormek stands behind the quality equipment they make, and if there is a problem they will fix it.

Affinity will contact Tormek Sweden as they need to be involved, especially if there is a manufacturing defect they need to be aware of.

Tormek may be a little more expensive than other copy-cat grinders, but then a lot of times you get what you pay for, and that includes after the sale support and service.

Thank you to everybody who contributed to this thread, and to Jeff Farris who does an amazing job with this forum.

[Elden]

Grepper,
You are correct. Circumference = Diameter times Pi
10 x 3.14 = 31.4 inches
That would be 31.4 inches per revolution.

However, I believe your RPM for the T7 is 90 rpm.
31.4 x 90 =  2826

So approximately 2826 inches per minute or
2826 / 12 = 235.5 feet per minute.

Inches per second = 2826 / 60 = 47.1 inches per second
Feet per second = 235.5 / 60 = 3.925 feet per second

Revolutions per second = 90 / 60 = 1.5 revolutions per second.

Now, am I confused?!

I had to go to my recliner and use the calculator, now I believe  it's correct.