Wheel 'bobbing' on new tormek

[Paracelsus462]

I noticed early on with my T-4 there was an area 75% to the right of the wheel which had a 'rough patch'. I assumed early on that I did something wrong I did not understand, and I waited for it to erode as the wheel was trued over time. Instead, the rough patch always persisted. Recently I decided to get the TT-50 truing tool, in part to solve this issue. As I ran the cutter across the wheel, it was doing a good job but suddenly once it approached that area the whole machine started to pulse/groan and I realized what was happening. On a micro-scale, the wheel is not revolving flush around the center. There is a high point, where the surface of the wheel bobs up/down on a micro scale, and trying to push the cutter across it was forcing it to oscillate from the 0.01" cut, to who knows how deep? It's deep enough that I can feel it with my fingertip as I run it across the surface. I guess the 'rough patch' I always noticed was from my tools attempting to sharpen in this bobbing area. I have had my tormek for 8 months now but I know the problem has always been there, I just finally know why. Where do I go from here... thanks

[Ken S]

Welcome to the forum, Paracelsus462.

I have two suggestions for users with grinding wheel problems:

First, email Tormek support (support@tormek.se). Support does an outstanding job.

Second, try using your new TT-50. Make sure you secure it to the universal support bar. Set the cutting depth for a very shallow cut. You want to just barely touch the high spot. Plan to make a number of very shallow passes.

First, contact support.

Keep us posted.

Ken

[Ornias]

Besides the obvious advice of contacting support:
There are roughly 3 kinds of wobble:
1. A bend axle
2. A stroke in the drive wheel
3. An not-true-round wheel

They have different symthomes which are quite doable to seperate:
1. In that case both wheels (the drive/honing wheel on one side and the stone on the other), wobble in tandem, but often slightly or completely offset.
2. In that case if you rotate the drivewheel on its own (or role it on the ground) it starts to wobble in itself too. But if you look at the shaft or stone seperately there is not wobble
3. In that case the stone is either not completely round, or isn't sitting straight on the axle.
3.a In case of not completely round, you would only notice a wobble in height, not to the sides. This is quite normal for example in Lathe operation and easy to fix: Put the TT-50 on slightly above the highest spot and slowly lower it bit by bit every pass.
3.b. In case the stone is not sitting nice on the shaft, you will also notice a wobble to the sides. It's not wise to fix this using the TT-50, because it might be related to the fit of the stone (and thus might change when you remount the stone.

[RickKrung]

How were you truing the stone if you didn't/don't have the truing tool? 

What is the nature of the roughness?  Does it have a regular pattern, like the diagonal lines in the photo below.  Those are a result of chatter by the truing tool during truing.  One thing to do to help is to grasp the truing tool as it crosses the stone - without putting downward pressure - to help dampen vibration.  Some have added cable ties/zip ties through the cutter head around the frame.  The new version of the truing tool may also help with this.  There was one member who build a steadying bracket.

0.01" seems like a bit of a too deep cut.  I can't say how deep the cuts are that I take, but the width of common copy paper is about 0.004" and it seems like my cuts are not as deep as that. 

As has been suggested, take only the very slightest/least cut you can, so that it cuts down the high spot only, continuing deeper with each subsequent cut until the high spot is gone and you are cutting uniformly across the entire width of the stone. 

[Paracelsus462]

I will try to reply to these responses altogether-

1. I will email Tormek support, thanks for the email address

2. I did use the TT-50 all the way across the wheel, at the 0.01" depth using the microadjust wheel. The TT-50 recommends a depth of cut in the manual between 0.01 - 0.03", so I took the smallest recommended cut. I now realize I did not correctly describe my situation - I do not have a high point at the 'rough spot'. It is the opposite. It is a low point. The sharpening wheel bobs vertically at this location, which forces the TT-50 to cut deeper into the wheel. This creates a valley in the wheel. I called it a high point because the wheel tries to bob higher, but really what this causes is a scar into the wheel. Because the vertical bobbing is periodic, the depth of the valley varies around the circumference of the wheel. Before I used the TT-50, the 'rough' spot looked... I guess rough and patchy, unlike the rest of the smooth face. No lines it just looked more worn. After the TT-50 it looks like what you would expect if you forced the TT-50 to cut deeper into your wheel in one spot as it revolved. Some chatter, white vertical scraping lines.

3. When I referred to 'truing' the wheel before I had the TT-50, I just meant using the tormek grading stone to clean up the surface, which I do periodically because I use the marker method often for my roughing gouge. I assumed that using the grading stone over time the rough patch would go away. But it never did. This must be the result of the wheel bobbing up into my tool as I sharpen it at this location.

[Ornias]

Okey, so to be clear:
It's not a wobble, it a vertical bobble?

In that case your stone is just a little untrue.
Just start your TT-50 truing tool based on the highest spot on the stone and move down from there every pass. It will get true eventually.

[Paracelsus462]

Okey, so to be clear:
It's not a wobble, it a vertical bobble?

In that case your stone is just a little untrue.
Just start your TT-50 truing tool based on the highest spot on the stone and move down from there every pass. It will get true eventually.

Maybe you are right, I'll try another pass at a smaller cutting depth.

Let's say right now taking depth measurements across the surface of my cutting stone it looks like this (0 being the flush surface with the majority of the wheel)

0 0 0 0 0 0 -1 -2 -1 0 0

Where the valley in the wheel was caused I believe by the wheel trying to move upwards into the TT-50 at this location

If I try to cut another distance of 1, we would be hoping for progress like this:

-1 -1 -1 -1 -1 -1 -1 -1 -2 -1 -1 -1

But I am worried that if the wheel is somehow bobbing at this trouble area, I will just repeat my experience last time and get this:

-1 -1 -1 -1 -1 -1 -1 -2 -3 -2 -1 -1

The part that the TT-50 struggles is not a high point. It's the dip in the wheel. Because it gets forced into it as the wheel bobs upwards. Otherwise it would just shave off the flush surface and skip over the valley.

[RickKrung]

Seems many of us disagree with the Tormek recommendations for cut depths.

Yup, start taking the high spot off small bits by bits, using much lighter cuts.  Start with it just barely touching in a small area (the high area).  Working your way until these light passes cut all the way across the stone and all the way around the circumference.  Light enough that it doesn't cause vibration but heavy enough that it is taking something off.

I have a hard time understanding how a rough patch could be due to wear.  Normally, wear smooths out the surface, even glazing it over. 

...snip...
I do not have a high point at the 'rough spot'. It is the opposite. It is a low point. The sharpening wheel bobs vertically at this location, which forces the TT-50 to cut deeper into the wheel. This creates a valley in the wheel. I called it a high point because the wheel tries to bob higher, but really what this causes is a scar into the wheel. Because the vertical bobbing is periodic, the depth of the valley varies around the circumference of the wheel.
...

I'm really confused.  The wheel bobs, with the high point being just that, high.  The truing tool would necessarily cut deeper in the hight area.  I do not see how this could create a valley.  It should only be reducing the height of the high point/area.  The truing tool would leave cutting marks, which you described later in your post.  These should not be regarded as scars.  They will even out with use.  Taking lighter cuts will reduce the depth of these cut marks and when light enough they will not appear as scars.  Oh, yeah, move the cutter across the tool more slowly to reduce the occurrance of these "scars".  If something else is what you mean, you'll might try again to describe it. 

The depth of the valley would be noticeable as the wheel turns, it would go either gradually or abruptly from high to low, but the depth of low spot would not vary/change.  As the truing action gradually reduces the high areas and reaches that low area, it should make the entire surface of the stone a uniform roughness and remove the roughness (make it all the same roughness).  If it does not, there might be a flaw in the stone, which Tormek should address. 

Rick

[Paracelsus462]

I'm really confused.  The wheel bobs, with the high point being just that, high.  The truing tool would necessarily cut deeper in the hight area.  I do not see how this could create a valley.  It should only be reducing the height of the high point/area. 

If we put a brand new, true wheel on my T-4, with everything else kept the same - then it would be a high point as it rotates/bobs around what I assume is some uneven shaft or something like that. Then say we run a TT-50 across the surface with 0 cut depth (flush with the normal majority of the surface). When it crosses this bobbing high point, it will gouge into it. The bob upwards causes it to push into the diamond cutter. And now there is a valley in the stone, relative to the rest of the surface. You can feel it with your finger.

[Paracelsus462]

Besides the obvious advice of contacting support:
There are roughly 3 kinds of wobble:
1. A bend axle
2. A stroke in the drive wheel
3. An not-true-round wheel

They have different symthomes which are quite doable to seperate:
1. In that case both wheels (the drive/honing wheel on one side and the stone on the other), wobble in tandem, but often slightly or completely offset.
2. In that case if you rotate the drivewheel on its own (or role it on the ground) it starts to wobble in itself too. But if you look at the shaft or stone seperately there is not wobble
3. In that case the stone is either not completely round, or isn't sitting straight on the axle.
3.a In case of not completely round, you would only notice a wobble in height, not to the sides. This is quite normal for example in Lathe operation and easy to fix: Put the TT-50 on slightly above the highest spot and slowly lower it bit by bit every pass.
3.b. In case the stone is not sitting nice on the shaft, you will also notice a wobble to the sides. It's not wise to fix this using the TT-50, because it might be related to the fit of the stone (and thus might change when you remount the stone.

I think it might be #1. This issue is on micro scale on the cutting wheel, but on my honing wheel I now notice I can visibly see the wheel bobbing.

Video: https://imgur.com/W6ywOFC

[cbwx34]

I think it might be #1. This issue is on micro scale on the cutting wheel, but on my honing wheel I now notice I can visibly see the wheel bobbing.

Video: https://imgur.com/W6ywOFC

If you can shoot video... take one of the stone.

I looked at your honing wheel video... the leather wheel is "bobbing"... but the drive wheel doesn't appear to be.  (You can remove the leather wheel, and just check the drive wheel).  That's the one that matters.

You can try this... mark the bad spot on the stone, loosen and rotate it a quarter turn... and see if the bad spot is still there (I don't know whether to call it high or low at this point).    Should help rule out if its the stone or shaft.

But what I find interesting is you call it a "rough patch".  If you used the grading stone (not TT-50), and it's not changing the surface texture in one particular area... that sounds like a stone issue, and that it's maybe wearing faster than the rest of the stone when you use it?

[Paracelsus462]

If you can shoot video... take one of the stone.

But what I find interesting is you call it a "rough patch".  If you used the grading stone (not TT-50), and it's not changing the surface texture in one particular area... that sounds like a stone issue, and that it's maybe wearing faster than the rest of the stone when you use it?

The deflection in the stone is so small it won't be visible on a camera. Enough to matter for sharpening or getting a smooth wheel, but not visibly bouncing. It wasn't until I heard the pulsing under the TT-50 cutter that I realized how much it was moving in that spot.

The TT-50 did cut all the way across and totally change the surface texture and color. But it also left a 'valley' in that spot of the wheel where it cut deeper (relative to the rest of the surface), because the wheel bobbed upwards into the cutter.

[cbwx34]

If you can shoot video... take one of the stone.

But what I find interesting is you call it a "rough patch".  If you used the grading stone (not TT-50), and it's not changing the surface texture in one particular area... that sounds like a stone issue, and that it's maybe wearing faster than the rest of the stone when you use it?

The deflection in the stone is so small it won't be visible on a camera. Enough to matter for sharpening or getting a smooth wheel, but not visibly bouncing. It wasn't until I heard the pulsing under the TT-50 cutter that I realized how much it was moving in that spot.

The TT-50 did cut all the way across and totally change the surface texture and color. But it also left a 'valley' in that spot of the wheel where it cut deeper (relative to the rest of the surface), because the wheel bobbed upwards into the cutter.

I guess I don't understand.  The TT-50 trues the wheel relative to the USB (support bar)... so even if the shaft was slightly off... the wheel should true to the USB?  (I'm asking... maybe I don't get it).

If the shaft was off, and you loosen and rotate the stone 1/4 turn... you should get a new high spot.  If you're seeing the issue in the same spot on the stone... that sounds like an issue with the stone... maybe the hole is no longer round (or never was)?

You can also mark the shaft and stone so it mounts the same each time... true it and see if it stays true.

[Paracelsus462]

If the shaft was off, and you loosen and rotate the stone 1/4 turn... you should get a new high spot.  If you're seeing the issue in the same spot on the stone... that sounds like an issue with the stone... maybe the hole is no longer round (or never was)?

You can also mark the shaft and stone so it mounts the same each time... true it and see if it stays true.

I'll do some more testing and take a new video tonight if I learn something, thanks all

[Ken S]

I think we are missing the logical answer. While this discussion would certainly be useful with an older Super Grind, Paracelsus' T4 and grinding wheel are still under warranty. I would let Tormek support (or Tormek Inc  if you happen to live in the US) handle things. There is no charge, and, while most of us have actually encountered this once, if at all, support has dealt with problems like this regularly for many years.

Ken