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In the Shop => General Tormek Questions => Topic started by: RickKrung on June 16, 2018, 06:16:15 pm

Title: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: RickKrung on June 16, 2018, 06:16:15 pm
Reading some of the posts in the SJ wheel discussion made me wonder, what does it matter if the stone is out of round a little bit?  At least for hand held jigs/operations. 

Using Wootz's applet, I checked to see what the angle change is for a 1mm eccentricity in the diameter (that is 0.5mm at the stone/edge interface).  For a stone at 245mm, 139mm projection and 16º starting angle and USB height of 169.12mm.  Changing the stone diameter to 244 and adjusting the angle until the USB height was nearly identical (USB 169.13mm), the angle changed to 16.3º. 

Assuming lateral travel is slow enough to expose an edge to the full excursion of the diameter at least once along the entire length, what does that angle difference mean to the sharpened edge?  A slight flattening of the concavity.  Less sharpening action at the apex.  Since we sharpen until there is a burr, the latter would mean it would take a little longer to raise that burr.  For production sharpeners, I can see that mattering, but to the more casual sharpener, like me, what does it matter? 

Rick
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: cbwx34 on June 16, 2018, 06:55:29 pm
Reading some of the posts in the SJ wheel discussion made me wonder, what does it matter if the stone is out of round a little bit?  At least for hand held jigs/operations. 

Using Wootz's applet, I checked to see what the angle change is for a 1mm eccentricity in the diameter (that is 0.5mm at the stone/edge interface).  For a stone at 245mm, 139mm projection and 16º starting angle and USB height of 169.12mm.  Changing the stone diameter to 244 and adjusting the angle until the USB height was nearly identical (USB 169.13mm), the angle changed to 16.3º. 

Assuming lateral travel is slow enough to expose an edge to the full excursion of the diameter at least once along the entire length, what does that angle difference mean to the sharpened edge?  A slight flattening of the concavity.  Less sharpening action at the apex.  Since we sharpen until there is a burr, the latter would mean it would take a little longer to raise that burr.  For production sharpeners, I can see that mattering, but to the more casual sharpener, like me, what does it matter? 

Rick

Actually, it's 16.295° ;)

The reality... probably doesn't matter as much as we're led to believe.  I'm sure if you're trying to achieve a very high level of sharpness, you might see some difference, but for the average sharpening, I'd say very little.  And it may be more important for some tools, other than knives.

There is a claim with regular waterstones that if not kept relatively flat, the issue will "compound" over time... in other words, the knife can start "digging in" to the stone more as it goes into the curve... getting dished faster.  Not sure if it would hold true with the wheel though.

My guess, is there's a lot of unsubstantiated reasons for it... with little supporting evidence.  One of those... if you can't tell, it doesn't matter, if you can, it does? ;)
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on June 16, 2018, 08:44:59 pm
Is this our forum machinist asking is it matters if the wheel is out of round? Does it matter if I drop my precision Starrett square on a concrete  floor?  :)

On a practical level, I suspect not. I doubt that many of the old Swedish large grindstones which inspired Torgny Jansson were round. Some of us, myself included, like to cut down the chance of error by eliminating as many gremlins as possible.

Ken
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: wootz on June 16, 2018, 09:03:15 pm
Rick, you will see you can't apex the edge when you change to the 2nd wheel.
E.g. you've bevelled and got the burr on an SG wheel that is a little out of round, then move to an SJ wheel to hone where won't be able to reach the apex in the portions of the edge that "ducked" by 0.3 degree on the SG - and where you are not able to reach the apex you can't deburr it at the same rate as the "proper" portions of the edge, so you keep honing and overhoning, and when you finally get to those "ducked" portions and deburr them, the edge apex on the other "proper" portions of your edge get ground off by overhoning, i.e. "rounded". At his point in time you logon to this forum to post a thread "why I cannot get a shaving edge off the SJ?".
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: jeffs55 on June 17, 2018, 12:59:45 pm
I have sharpened many knives on a wheel resembling an egg. A little out of round does not matter.
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on June 17, 2018, 05:42:32 pm
Jeff,

At the risk of being the devil's advocate, if you had to sharpen a knife and could choose between two Tormeks, Which one would you choose, the one with the wheel with the egg shaped wheel or the one with the freshly trued wheel?

I have certainly sharpened my share of tools with out of round wheels and not flat stones. I have also had gremlins which went away when I trued my grinding wheel. I spent my working life as a troubleshooter for Ma Bell. Whenever I don't find a source of the trouble, I try to eliminate possible trouble sources. Truing up the grinding wheel is a quick fix for a possible gremlin.

Ken
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: cbwx34 on June 17, 2018, 07:35:46 pm
Rick, you will see you can't apex the edge when you change to the 2nd wheel.
E.g. you've bevelled and got the burr on an SG wheel that is a little out of round, then move to an SJ wheel to hone where won't be able to reach the apex in the portions of the edge that "ducked" by 0.3 degree on the SG - and where you are not able to reach the apex you can't deburr it at the same rate as the "proper" portions of the edge, so you keep honing and overhoning, and when you finally get to those "ducked" portions and deburr them, the edge apex on the other "proper" portions of your edge get ground off by overhoning, i.e. "rounded". At his point in time you logon to this forum to post a thread "why I cannot get a shaving edge off the SJ?".

I'm not sure how being out of round would only affect portions of the edge?

Jeff,

At the risk of being the devil's advocate, if you had to sharpen a knife and could choose between two Tormeks, Which one would you choose, the one with the wheel with the egg shaped wheel or the one with the freshly trued wheel?
...

To me, it "feels" better sharpening on a trued wheel, and I'm sure is a more accurate and better edge, but maybe a better question would be, what difference would you see (especially in use)?  ???
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: jeffs55 on June 18, 2018, 05:03:53 am
Jeff,

At the risk of being the devil's advocate, if you had to sharpen a knife and could choose between two Tormeks, Which one would you choose, the one with the wheel with the egg shaped wheel or the one with the freshly trued wheel?

The freshly trued wheel every time. I do not remember how long it took me to notice the ever increasing ellipticity of my wheel. Is that even a word? It will work even when out of round but it is always better to use a tool in the correct way.
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: wootz on June 18, 2018, 11:50:41 pm
I have sharpened many knives on a wheel resembling an egg. A little out of round does not matter.

No doubt on your egg-shaped wheel you get a convex edge boasting fortified properties compared to the oversubtle edge off a trued wheel.
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: jeffs55 on June 19, 2018, 02:17:48 am
I have sharpened many knives on a wheel resembling an egg. A little out of round does not matter.

No doubt on your egg-shaped wheel you get a convex edge boasting fortified properties compared to the oversubtle edge off a trued wheel.
What the heck does that mean?
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on June 19, 2018, 03:02:27 am
Jeff,

My Australian is a little rusty. I think it means either "never needs sharpening" or "the shrimp’s on the barbe".  :)

Ken
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Grizz on June 19, 2018, 06:19:53 pm
i'll have the shrimp on the barbe while we wait !!!
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: jeffs55 on July 07, 2018, 08:28:25 am
My stepson just brought me his knife set for sharpening, Henckels or Wusthoff. Guess what? My wheel is egg shaped again. I have an aftermarket "truer" that has worked before, guess it will have to work again. I sure have not used it much for this to happen.
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on July 07, 2018, 11:13:46 am
Jeff,

I wonder if your shaft might have become bent. I remember Jeff Farris posting that he always removed the grinding wheel(s?) of his Tormek(s?) whenever he traveled. At one time he was traveling thirty four weeks a year. And, that was before the left hand thread EZYlock when you needed a hammer and a wrench to loosen or tighten the nut.

Machinery rebuilder Robert Vaughn wrote an article for Fine Woodworking where he routinely checked the straightness of drill press shafts with a dial indicator. He would hit the shaft with a hammer until it was straight.

A dial indicator would quickly check your shaft. If you do not have one, a local machinist, auto machine shop or motor repair could easily do it. Or, you could remove your grinding wheel. Set the usb in close. Place a piece of wood, plastic, or metal between the shaft and the usb. (This is just like using feeler gages to set distributor points in the old days.) Slide your "feeler gage" in and out setting the usb until you feel a slight drag. Use your other hand to rotate the shaft by turning the leather honing wheel. If the shaft is straight, you should continue to feel the same drag. It the drag changes, your shaft is bent. Straightening a shaft with clamping pressure is no big deal. (This is another example of the value of knowing a good machinist.)

Plan B would be to just replace the shaft. It you have a pre EZYlock SuperGrind or T7and have been thinking of upgrading to a stainless steel EZYlock, this might be a goid time to do it. The EZYlock also includes a new set of bushings. I converted my first T7. It is not difficult. The hardest part iwas reprogramming  my brain  to think left hand thread.

Another Jeff Farris tip was to true the wheel frequently. As a Tormek demonstrator, Jeff wanted to avoid problems. Keeping his wheel trued was a good way to lessen the number of problems.

Do keep us posted. I think your solving the egg shaped wheel problem will benefit many readers.

Ken

ps your package is being mailed tomorrow..
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Jan on July 07, 2018, 01:11:26 pm
In my understanding an oval grindstone is today rather a curiosity. In ancient times it was probably used to grind a convex grind on swords.  ;)

It is not so easy to imagine how an oval stone works, and so sometimes ago I have prepared a model. I have assumed that the oval is an ellipse with axes ratio 4:5. The blade is guided by a jig which fixes the blade protrusion from a pivot.

Assume that when the vertex of the oval stone meets the edge than the wheel grinds the desired bevel angle.

When the stone rotates towards the co-vertex, than the contact point with the blade moves away from the edge and the bevel angle changes its size.

When the co-vertex of the oval stone meets the edge than we have reached spot where the change of the bevel angle is maximal.

Jan
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: cbwx34 on July 07, 2018, 02:30:20 pm
I like that model.

So, if a wheel is slightly out of round, will it offset the hollow grind, and produce a flat grind? ??? (Not that the hollow grind really matters)...

My stepson just brought me his knife set for sharpening, Henckels or Wusthoff. Guess what? My wheel is egg shaped again. I have an aftermarket "truer" that has worked before, guess it will have to work again. I sure have not used it much for this to happen.

Maybe your stone wears faster in certain areas?  What about marking either the high or low spots... and see if they reappear in the same area?  (And if it's a bent shaft like Ken suggests, you could rotate it 90° on the shaft, and see if it changes anything).
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: AKMike on July 07, 2018, 08:47:55 pm
Are you taking the wheel off your Tormek after you have trued it and made it round again? If so, you may want to try marking the wheel and the Tormek so that you always replace the wheel in the same orientation.

Mike
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Grizz on July 07, 2018, 08:58:56 pm
good idea AKMIKE  !
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Jan on July 07, 2018, 09:06:43 pm
I like that model.

So, if a wheel is slightly out of round, will it offset the hollow grind, and produce a flat grind? ??? (Not that the hollow grind really matters)...

CB, I do not expect a flat grind.
Jan
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on July 07, 2018, 10:42:42 pm
Jeff Farris and I had a private joke to describe this kind of debates: "How many angels can dance on the head of a pin?" At one time the way you answered questions like these could put your life in peril with the Inquisition. 

I predict we will have another resurgency of the old flat vs hollow ground debate when the new diamond wheels arrive. Having a flat grind option will be new for Tormek. The diamond wheels still have the same large 250mm Tormek diameter. While my logical side recognizes this as hollow ground, my eyes have difficulty seeing it.  It will be an interesting debate.

Ken.
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: RickKrung on July 08, 2018, 12:46:33 am
Jeff,

I wonder if your shaft might have become bent. I remember Jeff Farris posting that he always removed the grinding wheel(s?) of his Tormek(s?) whenever he traveled. At one time he was traveling thirty four weeks a year. And, that was before the left hand thread EZYlock when you needed a hammer and a wrench to loosen or tighten the nut.

Machinery rebuilder Robert Vaughn wrote an article for Fine Woodworking where he routinely checked the straightness of drill press shafts with a dial indicator. He would hit the shaft with a hammer until it was straight.

A dial indicator would quickly check your shaft. If you do not have one, a local machinist, auto machine shop or motor repair could easily do it. ...snip...

 Straightening a shaft with clamping pressure is no big deal. (This is another example of the value of knowing a good machinist.)

Plan B would be to just replace the shaft. It you have a pre EZYlock SuperGrind or T7and have been thinking of upgrading to a stainless steel EZYlock, this might be a good time to do it. The EZYlock also includes a new set of bushings. I converted my first T7. It is not difficult. The hardest part was reprogramming my brain  to think left hand thread.
...snip...
Do keep us posted. I think your solving the egg shaped wheel problem will benefit many readers.

Ken
...snip...

I'm having a hard time with some of this. 

First, it is difficult for me to imagine how a shaft could become bent through merely transporting it with one of the grinding wheels on it without the machine/stone being dropped.  Did Jeff Farris ever say why it was that he removed the wheels for transport?  I remove the stones from the machine when transporting to make handling of each easier as much if not more than being concerned about the shaft.  I am much more concerned about the stone being damaged through hitting it while lifting/moving it, or if it shifted in the vehicle during transport.

In order for the shaft to become bent in a drop, I would think there would be such substantial damage to the case and probably the wheel, that much more than the shaft would need replacing. 

Second, I have a very serious problem with the notion that whacking the exposed part of a drill press spindle with a hammer can straighten it, especially without causing serious damage to other parts of the spindle, in particular the spindle bearings.  I put it this way because the image I got from your statement about Robert Vaughn's method is of him hitting either the drill chuck or the spindle taper with a hammer while the spindle is still installed in the quill in the drill press.  Please tell me this is not how he does it. If I saw someone treating my drill press like that, I would immediately separate the two by substantial distance and never let that person near any of my machines or tools again. 

The right way to straighten a shaft, such as a drill press spindle is with it removed from the machine and with it supported on either side on precision blocks and slowly bent in a hydraulic press using a dial indicator to show the amount of bending.  Followed by rotating the shaft under a dial indicator, again supported on precision blocks ("Vee blocks"), to show the extent of straightening achieved and followed by bending again, as necessary, with the same setup. 

I did this once when restoring my pre-WWII Rivet 1020 metal lathe that had helical bevel gears mounted on counter-rotating shafts in the headstock which controlled the direction of travel of the carriage. I did not have a hydraulic press so I used the quill of my vertical mill. 

Indicating the runout.  Numerals on the indicator are 0.001".  Hash marks between the numerals are 0.0001". 
(https://www.tormek.com/forum/index.php?action=dlattach;topic=3645.0;attach=2406)

Shaft straightened and headstock workings reassembled. 
(https://www.tormek.com/forum/index.php?action=dlattach;topic=3645.0;attach=2408)

The restored lathe is my Avatar photo.  Here it is before we started the restoration.
(https://www.tormek.com/forum/index.php?action=dlattach;topic=3645.0;attach=2410)

And when it was finished.
(https://www.tormek.com/forum/index.php?action=dlattach;topic=3645.0;attach=2412)

A lot more than shaft straightening when into that.  Took two years.  It was my pride and joy, home shop machinist's dream machine.  A few commented that it belonged in the Smithsonian. 

Rick


Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on July 08, 2018, 03:00:21 am
Rick,

Considering that I read the article over twenty five years ago, I might not have all the details correct. I will leave the reply posted, but will add a caveat that the soirce may be misquoted.

Ken
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: RickKrung on July 08, 2018, 04:46:08 am
Rick,

Considering that I read the article over twenty five years ago, I might not have all the details correct. I will leave the reply posted, but will add a caveat that the soirce may be misquoted.

Ken

I looked at Fine Woodworking.  I had to re-up to get access to the whole article, but here is a quote from what I'd say is probably that article:

Correcting wobble with a smack

Rather than replacing your machine's most expensive parts (quill,
spindle and chuck), you may be able to smack wobble out (see the
bottom photo). Since a shock force knocked things out of alignment,
an equal-and-opposite blow (within reason) can line things
up again. Move the arm of the indicator out of the way, and then
mount a hefty steel rod in the chuck and put on your safety glasses.
Position the chuck so you can smack the rod directly opposite
your mark, Your first tap should be a light one-similar to driving
a 3/8-in. brad into soft pine. Chuck your precision rod, reposition
the plunger and rotate the spindle to observe any change. Repeat
until you've got less than .002-in. wobble.

(https://www.tormek.com/forum/index.php?action=dlattach;topic=3645.0;attach=2416)

Not an unreasonable approach.  And not the horror that I imagined.  No surprise.  I think this would only work with modest amounts of runout.  I'd still take the spindle apart and figure out just where along it the bend is and work on fixing that more directly. 

I downloaded some of his other articles.  I am particularly interested in the one on fine tuning a bandsaw as I've just installed Carter precision guides on mine and am interested in all the info I can get. 
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: RichColvin on July 08, 2018, 10:39:52 pm
Rick,

That is an AWESOME restoration! Looks great.

Kind regards,
Rich
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: RickKrung on July 09, 2018, 04:09:56 am
Rick,

That is an AWESOME restoration! Looks great.

Kind regards,
Rich

If you are interested, more photos of it here: 
http://users.easystreet.com/krugerr/Machining/Rivett/Restored/ (http://users.easystreet.com/krugerr/Machining/Rivett/Restored/)

Rick
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Wyo6050 on July 09, 2018, 05:39:37 am
Wow Rick-  Like others have said, sweet restoration on that lathe!

This thread interested me since my stone too seems to end up getting out of round.  I was going to post a thread about it but haven't had the time. so thank you for this one.

My T4 is only a few months old and I figure I have 10-12 hours on it.  I've had to redress the SG-200 three times now because it started to get egg shaped.  Is that normal or is my technique causing it to go humpty dumpty?   

When you folks put it away for storage- as in wont be using it for several weeks to longer, do you take off the wheel? I have avoided taking the wheel off since it was trued to its current position and I don't want to take more wheel off if I don't have to.

The last truing I did, I noticed that the TT-50 slanted the wheels grinding surface.  I'm at a loss for what to call it so I'll just say it didnt square it up to the sides of the wheel and there is a little sliver of light when the USB is up against the wheel.  I need to figure what caused that but I have my suspicion that I didn't set the USB correctly.  I discovered there is a slight play in the usb going into the locking holes.  Next time I bring it out I'll look at it closer.

Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: RickKrung on July 09, 2018, 08:16:43 am
Wow Rick-  Like others have said, sweet restoration on that lathe!

This thread interested me since my stone too seems to end up getting out of round.  I was going to post a thread about it but haven't had the time. so thank you for this one.

It might behove you to start a new thread with your questions, as this thread may be "worn out" and guys aren't paying much attention anymore.  There is a tremendous collective knowledge here and it would be good for your questions to be seen by as many as possible.  I will speak to what I think I know.

My T4 is only a few months old and I figure I have 10-12 hours on it.  I've had to redress the SG-200 three times now because it started to get egg shaped.  Is that normal or is my technique causing it to go humpty dumpty?

I wouldn't think getting egg shaped that quickly is normal.  Hard to comment on whether your technique is causing it.  I've not actually had problems with my stones going egg shaped.  My original post in this thread, my SJ wheel was only about 1mm out of round, which I would not characterize as egg shaped.  I have trued them more to refresh their surface than remove egg shaped-ness.

When you folks put it away for storage- as in wont be using it for several weeks to longer, do you take off the wheel? I have avoided taking the wheel off since it was trued to its current position and I don't want to take more wheel off if I don't have to.

I do both, take a stone off and sometimes leave it on.  I sometimes leave a stone on the machine so it will dry.   

I change stones between SB, SG and SJ, so stone changes are a regular thing.  I've marked all the components to help with aligning them as they were when last trued.  I have marked the end of the shaft and the backing washer with center-punches. I've used white paint marker on the inside surface of the leather honing wheel and marked a "vertical" position on the labels of each stone.  I align these all went putting a stone on, for use or truing. 

The last truing I did, I noticed that the TT-50 slanted the wheels grinding surface.  I'm at a loss for what to call it so I'll just say it didnt square it up to the sides of the wheel and there is a little sliver of light when the USB is up against the wheel.  I need to figure what caused that but I have my suspicion that I didn't set the USB correctly.  I discovered there is a slight play in the usb going into the locking holes.  Next time I bring it out I'll look at it closer.

First, I believe I've read and/or viewed how we should set the USB height by tightening the threaded upright with downward pressure on the top of the USB above the upright.  Then tighten the other upright without pressure anywhere.  I do this, but I also check that the USB is perpendicular with the sides of the stone using a machinist's square (but any good square will do) before truing.  I'd do that too with the square edge jig and others that rely on being square, but I haven't used them that much. 

Second, you didn't specify which side of the stone surface had the light shining through, left/inside or right/outside.  If it was the left/inside, then you may have a problem with the USB not lining up properly in the clamps.  If it was the right/outside, it is possible you put pressure on the outboard side of the truing tool/USB during truing.  I think the proper technique is to touch/rotate only the thumb screws when truing, avoiding resting your hands so as to avoid pressing down on the unsupported outside-side.  This is part of the reason I developed a motorized truing tool.  Both rely on a properly aligned USB. 

Hopefully, you will hear from several others.

Rick
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on July 09, 2018, 02:02:05 pm
I am starting to wonderif I havemisinterpreted "egg shaped". I would interpret egg shaped to mean not having a consistent radius if a compass was laid flat on the grinding wheel. I would interpret crowned to be if the grinding wheel had a high spot in the middle and tapered if one side was lower than the other.

I think it is good practice to regularly eliminate any of these problems.

Ken
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: cbwx34 on July 09, 2018, 02:25:19 pm
...
This thread interested me since my stone too seems to end up getting out of round.  I was going to post a thread about it but haven't had the time. so thank you for this one.

My T4 is only a few months old and I figure I have 10-12 hours on it.  I've had to redress the SG-200 three times now because it started to get egg shaped.  Is that normal or is my technique causing it to go humpty dumpty?   

When you folks put it away for storage- as in wont be using it for several weeks to longer, do you take off the wheel? I have avoided taking the wheel off since it was trued to its current position and I don't want to take more wheel off if I don't have to.

The last truing I did, I noticed that the TT-50 slanted the wheels grinding surface.  I'm at a loss for what to call it so I'll just say it didnt square it up to the sides of the wheel and there is a little sliver of light when the USB is up against the wheel.  I need to figure what caused that but I have my suspicion that I didn't set the USB correctly.  I discovered there is a slight play in the usb going into the locking holes.  Next time I bring it out I'll look at it closer.

I think a lot more info would be needed... what do you sharpen, do you make repairs on tools, do you grade between coarse/fine often... etc.  Also, what do you consider "egg-shaped"... something you notice obviously, or something you have to, for example, compare against the USB to see it?

To answer at least one question... I rarely remove the stone... and it has sat on my older machine for years with no problems that I could tell.  I suspect that most leave the machine stored with the wheel mounted... considering Tormek makes a cover (https://www.tormek.com/usa/en/accessories/other-accessories/mh-380-machine-cover/) to store the machine, I would think this is the norm?

BTW, I happened to notice the other day that the holes for the horizontal USB position, don't have the "play" that the vertical holes do.  Has anyone else noticed this?... and any thoughts on truing the stone from the horizontal position?  (I haven't tried this yet).  Kinda weird that there is a difference in shape between the two positions...  ???
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: cbwx34 on July 09, 2018, 02:35:09 pm
Rick,

That is an AWESOME restoration! Looks great.

Kind regards,
Rich

I agree.... that restoration looks amazing!!!  8)
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Wyo6050 on July 09, 2018, 03:21:38 pm
Rick & cbwx34,

Thank you for the reply and tips for setting the USB.  Light is showing on the left/inside.

The first time it got out of round was when it was under 2 hours of use.  I've been sharpening hand plane blades, bench chisels and turning tools to include skews, gouges, and scrapers.  Nothing too serious. If I had to remove a lot fo metal I ran it trough the slow speed grinder first and then touched it up on the T4.  I could feel the high point in the wheel while applying pressure on the item being sharpened and see it as it made its rotation.  Since then I have paid more attention to it after I trued it out.  The wheel started to do it again, I could hear it and feel it while grinding.  I do grade between the coarses and noticed that sometimes the wheel 'grabs' the stone grader, makes a rotation and grabs it again.  I believe the spot(?) that is grabbing is a flat spot created either by the stone grader or a flaw in the stone as the metal trail in the stone after sharpening doesn't show any gaps or problems where the wheel isnt against the tool. That's another thread though. I don't think I was pressing too hard.  Then just recently while doing a hand plane blade it started getting out of round again.

I think that play in the vertical position is what caused the slant in the wheel.  My horizontal holes seem to be solid.



Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: jeffs55 on July 10, 2018, 08:39:14 am
I am starting to wonderif I havemisinterpreted "egg shaped". I would interpret egg shaped to mean not having a consistent radius if a compass was laid flat on the grinding wheel. I would interpret crowned to be if the grinding wheel had a high spot in the middle and tapered if one side was lower than the other.

I think it is good practice to regularly eliminate any of these problems.

Ken
You are correct, that is what has happened to my stone. I have not mucked with it yet but would say that a bent shaft would not cause my problem. A bent shaft would change the left to right motion of the wheel. In order for it to affect up and down, well you simply cannot bend the shaft like that. It would have to be bent like a crankshaft with the wheel being in another plane. I have yet to remove the stone in order to check. I am in GA and it is so hot here that I just burst out into a big sweat by opening the doors to the house!
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on July 10, 2018, 02:48:56 pm
Jeff,

I think many (most) Tormek users are afflicted with what I call the "precious grindstone syndrome". I am old enough to have ancient memories of the cost of a replacement six inch grinding wheel from my local store several decades ago. Compared to that, the cost of an SG-250 seems astronomical. However, looking a little deeper, The SG has a diameter of 250mm and a thickness of 50mm. It is physically much more grindstone. It is produced in much smaller numbers and is probably specially formulated. If we compared its cost with the same size grindstone from Norton purchased today, the cost would not seem so excessive.

We all suffer from a deep seated belief that grading the stone will shorten its life, and even worse, truing it will lessen its useful life even more. If we carry that logic even further, even sharpening with it shortens its life. This causes us to try to avoid grading and truing.

I have been criticized for suggesting frequent and light truing. I want my grindstone cutting at near 100% efficiency. With frequent and light truing, it will remain close to full efficiency. With practice, the truing operation becomes very efficient. I don't think most of us true often enough to ever develop that fluency and confidence. We do not wait until our knives will not cut butter to sharpen them; why do we procrastinate in maintaining our grindstones?

Ken
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: cbwx34 on July 10, 2018, 03:00:23 pm
... I could feel the high point in the wheel while applying pressure on the item being sharpened and see it as it made its rotation.  Since then I have paid more attention to it after I trued it out.  The wheel started to do it again, I could hear it and feel it while grinding.  I do grade between the coarses and noticed that sometimes the wheel 'grabs' the stone grader, makes a rotation and grabs it again.  I believe the spot(?) that is grabbing is a flat spot created either by the stone grader or a flaw in the stone as the metal trail in the stone after sharpening doesn't show any gaps or problems where the wheel isnt against the tool. That's another thread though. I don't think I was pressing too hard.  Then just recently while doing a hand plane blade it started getting out of round again.
...

My only thought is what I mentioned somewhere else... perhaps mark the location of the flat spot on the side of the wheel... and see if it reappears at the same location?  Whether or not Tormek sees this as a flaw that they would replace... you would probably have to email Tormek support and ask them.
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: jeffs55 on July 10, 2018, 03:43:22 pm
[

My only thought is what I mentioned somewhere else... perhaps mark the location of the flat spot on the side of the wheel... and see if it reappears at the same location?  Whether or not Tormek sees this as a flaw that they would replace... you would probably have to email Tormek support and ask them.
I will do that, if I can determine the location of the "flat spot". It would be interesting to know if it always appears in the same place. It could well be a problem with the mixing of the slurry that composes these stones. Having used mine for many years, I am not going to pursue a replacement. As for Ken, you are right about me and so many others. I can't get past the purposeful degradation of the stone. I mean, you do not turn your brake rotors when it is not needed in an effort to make them last longer. On the other hand, I can see where increased performance as in less time grinding would make the stone last longer. Then it goes back to taking that away by grinding off the surface. I will true mine as it annoys me to see the rise and fall of the wheel and just knowing that it is not right. Gotta let it cool off some or bring the Tormek indoors. With the little grinding that I do, it can wait.
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Ken S on July 10, 2018, 04:22:02 pm
Jeff,

I worked out a procedure for maintaining a constant rotational of the grinding wheel. I start at the dry end, marking an up arrow on the side of the drive wheel and leather honing wheel. This fixes the position of the shaft. With that fixed, an up arrow drawn on the grinding wheel at the optimal position fixes everything. When the grinding wheel is switched, make sure the arrow continues to point up.

A refinement of this would be to also mark an up arrow on the dry end of the shaft to make sure the tested rotation point was preserved during bushing regreasing. In the mechanic/machinist world, these arrows would be called "witness marks". Whether we like it or not, the deeper we venture into the precision sharpening capabilities of the Tormek, the more we must understand of the mechanic/machinist world.

I understand your brake rotor analogy. I think the brake pads would fit better. Every time we use our brakes instead of just removing our foot from the accelerator, we degrade (cause wear) on our brake pads. Every time we sharpen a knife, we remove metal, thus degrading it. Am I suggesting we stop using the brakes on our car or not sharpen our knives? Of course not. Sadly, our Tormek grinding wheels, like operators, are not immortal.

On a practical level, many light truings will have minimal effect of the wheel size. I start with a very light cut which barely touches the high spot. I continue with very light cuts (half a micro adjust number) until such a light cut become continuous. At that point the wheel is true. No more "one pass more for good measure”.

Ken
Title: Re: What Does It Matter If The Stone Is Out-Of-Round A Little?
Post by: Grizz on July 12, 2018, 02:16:33 am
same here Ken. ! :)