Helical striations during resurfacing

[gkast]

I run the shops at Palomar College and we have 8 Tormeks in our shops here.   A question has come up regarding the helical striations that sometimes show up when truing up the grind wheel (see attached photo).   The grooves associated with the striations are significant and may affect the performance of the stone during the sharpening process.  Note that these striations appear regardless of how slowly the truing diamond is run across the wheel.   Could this be a defect in the stone?

[micha]

Hi Georg,

welcome to the forum.
Do you see these striations on each of your machines? I've seen similar traces when there was a lot of chattering while truing the wheel.
And I remember quite a similar pattern on a SJ stone, but not on SG, as long as the truing went smooth and without vibration/chatter.

Which version of the truing tool do you use? There are two around, the older one being more prone to chattering.

Mike

[Ken S]

Welcome to the forum, Georg.

I emailed Tormek USA about your grinding wheels. Here is their reply:

"Too little pressure between the diamond tip and stone. If thishappens, flatten with the stone grader and then apply a little more depth."

Ken

[gkast]

Thank you - in this latest incidence, the instructor was taking a light cut consistent with the instructions ~.01" and took more than 90 seconds to complete the pass, then repeated the process.   The TT-50 indicates that a heavier cut can be taken (.03").   I will experiment with different depth of cuts and grinding times on the wheel exhibiting the anomaly after spring break.

[sharpening_weasel]

Hiya! I've had the same problem. Check out the knife grinders Australia YouTube video- I've used the same techniques (zip tie and reversing direction of cutter) and found that cleared up around ninety percent of the helical chatter.

[RickKrung]

Welcome to the forum.  With that many machines and users, you should study a lot of what is on this forum's history of topics and posts.  You will find many answers to questions you don't know yet that you have. 

Many of us have had these striations.  I found mentions of it as far back as 2012 but likely it came up earlier than that.  I had them early on (late 2017).  It is lack of rigidity, in my opinion.  This results in chatter and can be very difficult to eliminated, as well as the striations.  I believe it was early 2018 when this received a good bit of attention.  [I stand corrected] Wootz (ala Knife Grinders) Ionut was the first to add a zip-tie to the truing tool to reduce the looseness between the cutter head and jig body.  I re-manufactured the whole truing tool and motorized it.  With the motorization, I typically take 2-4 minutes to traverse the stone - while taking VERY light cuts.  I doubt I take more than 0.001-0.002" often.  I cannot imagine taking cuts as heavy as 0.01-0.03".  Such heavy cuts would cause quite a bit of vibration and thus chatter. 

One solution I've found helps is to hold the outboard end of the USB while the tool is traversing, without putting downward pressure..  Difficult to hold in this manner, particularly for as long as I traverse.  But it helps eliminate the chatter.  One member built a support for the outboard end, which I think is a good idea, just hard to implement with the small increments of adjustment needed when successively setting the USB for a deeper passes.  I have wanted to do this for a long time, just haven't. 

In 2019, Tormek modified the truing tool, I think in part or largely, to address this issue, so getting and using the updated truing tool should help.  That will not necessarily prevent it from happening with new or un-striated stones, so do what you can to keep the USB bar from vibrating should help.

Rick

[gkast]

Thank you all for your responses and links to reference material.

[RickKrung]

I run the shops at Palomar College ...snip...

I grew up in Solana Beach and had graduated San Dieguito HS in '65.  I attended Palomar College '65-68 before transferring to UC Davis.  It was a simple place then, as were most.  That was the last time I lived in SoCal., but the time there were the most idyllic of my life.  I recall overhearing some adult comment, sometime in the '50s that "Someday the entire coast will be built up/in and the only open space remaining will be Camp Pendleton.  I could not fathom it, but it became reality much too soon.  I had a hard time returning after about 1972.  I still visited, still had family there, but it was never the same.   

I never took any shop classes at Palomar, or in high school.  My father was a machinist and he had put me to work in his shop when I was in high school.  Whenever I visited, I always came with a project I wanted to do.  I started my own hobby machine shop in my basement in 2000. 

Sorry, a bit off-topic.

Rick

[Dutchman]

... snip
Sorry, a bit off-topic.
Rick

Off topic, but with a feeling that I also experience in my environment. It will be our age to blame.

[RickKrung]

... snip
Sorry, a bit off-topic.
Rick

Off topic, but with a feeling that I also experience in my environment. It will be our age to blame.

Thanks.  I beg to differ, however...   "our age to credit..." 

Rick