Grinding wheel surface issues - Resolved

[grepper]

Hi Kb0rvo,

Thanks for the correction!

I checked my T-7 manual.  Yup.  90 rpm not 150 rpm.  I was probably thinking about one of the wanna-be a Tormek  grinders I had looked at.

Makes sense to me:

Using 90 rpm:
30 X 1.5 / 12 = 3.75 fps

Oh no!  Forgot to mention that I've removed maybe 3 mm of my stone with the truing tool!

Cheers,

Mark

[Mike Fairleigh]

I went through a layer on my wheel where there were large patches with a lighter discoloration.  As far as I can tell it didn't affect operation and now I seem to be through that layer, but I'm still keeping an eye on it.

[grepper]

My wheel has a bunch of areas where the surface decomposition has occured.  A long 4" one on one edge, and a bunch of other elongated patches.  And yup.  They are lighter in color and look like new wheel compound has been exposed.

The weird thing is just how "grabby" these areas are!

Mark

[Elden]

Mark,
You are making this to be fun! There are 25.4 mm in an inch, so to convert a loss of 3 mm to thousandths of an inch:

3 / 25.4 = 0.118 inch loss (0.007 inch less than 1/8 inch)

10 - 0.118 = 9.882 inches (present wheel diameter)

9.882 x 3.14 = 31.03 circumference inches or number of inches per revolution

31.03 x 1.5 = 46.55 inches per second or 46.55 / 12 = 3.88 feet per second

31.03 x 90 = 2792.7 inches per minute or 2792.7 / 12 = 232.73 feet per minute

That's all in fun, but it is interesting. I never thought about a soft spot on the wheel giving the the action you have described. Thanks for posting the warning.

[Jeff Farris]

My wheel has a bunch of areas where the surface decomposition has occured.  A long 4" one on one edge, and a bunch of other elongated patches.  And yup.  They are lighter in color and look like new wheel compound has been exposed.

The weird thing is just how "grabby" these areas are!

Mark

Mark,

This sounds more like your grading was not thorough enough.

[grepper]

Jeff,

I really hope I'm not just being an bonehead.  Here are a couple of more pics.  It's a little hard to tell from the pics, but these areas are depressions, and it takes a _lot_ of grading to really get them to diminish.  I have resurfaced the wheel a bunch of times with the truing tool and then regraded.  It starts out ok, but then these areas return.

http://www.screencast.com/t/8cXpeUnqC6
http://www.screencast.com/t/hRcYVFC5

Really appreciate your input.  If you are correct then I feel like a goof.

Mark

[grepper]

After I contacted Affinity Tool, the company handling warranty issues, they got back with me the next day just as they said they would.  They are shipping a replacement wheel, complete with a FedEx pickup ticket for the old one.  The old one will be shipped back to Sweden so manufacturing can check it out.

If with the new wheel I still suffer the same problems and it this turns out that I simply wasn't grading enough, then I shall surely feel to be a real bonehead.

I've got to say that Tormek and it's dealers couldn't have been more responsive or handled it more professionally.  A great product with amazing after the sale support and service.  I really couldn't ask for more.

Thanks too to everyone who participated in this thread! I had no idea it would still be going when I first posted the question.  

Mark

[Herman Trivilino]

These gouges are something I've never seen.  You would have had to abuse the stone to get those, so I would say that there is definitely something wrong with that grindstone.

[grepper]

Yea.  Weird huh. 

I would never knowingly abuse my beloved wheel!  In total it's seen maybe 30 knives, 20 hand pruners, a few pairs of scissors and a machete!  The machete was difficult to keep a consistent bevel as I had to move the jig.  Hey Tormek... how 'bout a machete jig! 

[jeffs55]

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.

If you are stuck with the defective stone, you can always grind with the wheel turning away from you. That way at least it will not throw the knife at when it grabs but rather toward the wall or someone else!

[grepper]

Received the new grinding wheel last night, complete with a pickup ticket for the old wheel.  Only a couple of days from first contact to new wheel.  Impressive after the sale warranty suppport, huh!

I had forgotten what a joy it is to use.  No problems using the grader to go between 220 & 1000 grit.  No grabbing at the grader stone.

The first thing I did was to repair a broken tip:
http://forum.tormek.com/index.php?topic=1516.0
Perfectly smooth, no jerking the knife with each wheel rotation.

Pretty exciting stuff - (especially if you have a low excitement threshold like I do!  ).

I'd say that about wraps this one up.

Tormek and it's dealer support have been exemplary.  Thank you!

Mark

[mski2]

I dont have that same problem but I have small chunks of stone coming off on the edges, were yours in the middle, I hardly used it

[Rob]

I've had that, but only tiny bits, spect its normal wear and tear

[Herman Trivilino]

In my experience that should happen only rarely.

Be careful with the truing tool.  Never work towards an edge when close to that edge.  It causes tear-out.

[Rob]

Herman are you saying only true from either end towards the middle?