Diamond wheel width inconsistencies?

[cbwx34]

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So, it seems 1 notch on the micro adjuster is equal to about 0.25mm of bar height, is that about right?  I know that info is out there somewhere, but I don't recall.
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Yep... that's correct.

Glad it's solved... well figured out anyway...

[Kavik]

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So, it seems 1 notch on the micro adjuster is equal to about 0.25mm of bar height, is that about right?  I know that info is out there somewhere, but I don't recall.
...

Yep... that's correct.

Glad it's solved... well figured out anyway...

Thanks for the confirmation on that.

Now if only I had a metal lathe to cut new backspacers to match each wheel......something tells me trying to shim with 0.2mm and 0.5mm washers isn't going to be a great long term solution lol

[Ken S]

Kavik,

Certainly not the ideal solution......

Instead of trying to make very thin spacer washers, I would just either machine or 3D print new spacer washers for each of the diamond wheels (thickness of original spacer washer + or - the correction factor).

Ken

[Kavik]

Yup, that's exactly what I meant by "Now if only I had a metal lathe to cut new backspacers to match each wheel" 

Sadly, i don't have the equipment to do that....I might know someone with a 3D printer who could help, but I wouldn't have expected plastic would hold up for that part?  Even my metal backspacer is showing some signs of wear....
Could be worth a try though 

[Ken S]

One of the joys of 3D printing is that a second backup washer is only a few clicks away. I'm superstitious; make a spare and your first one will never fail..........

Ken

[Kavik]

make a spare and your first one will never fail..........

Ken

LMAO  now there's some solid truth, right there 

[cbwx34]

I'd have to set it up and look at it, but it seems to me there should be a simple way to reference where the USB is in relation to the outside side of the wheel, and adjust it that way?  I think all you'd need is something you could lay across the wheel that you could then move the USB up against.  (That's in my head anyway...)   

[Kavik]

Yeah, I'm sure there are workarounds.  Again, it just surprised me that they were off like this, but i can set the angles okay if i re-adjust your reach wheel.

So far, I've only been using it to work on a set of chisels.  I could see a custom block for the USB height and chisel projection being the answer for that.

I'm hoping that i can use the turning tool jig and angle setter when it comes time for those, but I haven't even started looking into that.


Today I just discovered a new problem - the USB is shifting because the multi-base is racking in the mount after I lock it down.....because my old SG2000 only locks one side of the bar.  So, time to drill and tap that for a second lock screw 

[Ken S]

I once found and purchased a "bargain" XB-100 at my local Tormek dealer, only to learn that it was the older, single lock screw design. I would suggest purchasing the new two locking screw design XB-100. The sleeve walls are thicker, allowing better locking area pressure. The XB-100 is one of the least costly Tormek accessories.

I recall reading in the handbook Tormek's acceptable tolerance ranges axially and radially for the conventional grinding wheels. When you contact support, ask the tolerance ranges for the diamond wheels, including wheel width and flatness. Your wheels are either in tolerance or not within tolerance. Diamond wheels shouldn't wear. If yours are not in tolerance, mention that to support.

Ken

[Kavik]

I would suggest purchasing the new two locking screw design XB-100.

Y'lnow, i was debating about going that route instead, just this morning.....and then it occurred to me, i have one of these mounts already, out on the porch on my BGM-100 (for the high speed grinder, that I haven't used in ages).  I might just swap that over this weekend, if I find some free time.
Or wait till next week for a new mount and upgraded water tray to be delivered.  The side grinding definitely doesn't play well with the old SG2000's original water tray.....especially after i increased the speed of the machine today lol

Good question about the acceptable tolerances from the factory. I'll see about getting motivated to send that email this weekend too, if time allows.

[Kavik]

Finally got around to emailing tormek at the end of last week, and just heard back from them this morning. 

Was told the wheels themselves can vary up to 0.2mm in width (along the rim), and that they couldn't quote me all the other tolerances for backspacing, offset, etc.  But they're saying an overall difference of 0.5mm would still be within spec.

They signed off with "I am sorry, but it is very difficult for us to have tighter tolerances than that. This surface is not our primary grinding surface.", so I guess that answers the question; when they talk about consistency for swapping between wheels they're talking for face grinding only, not side grinding 


After spending more time with it this weekend, I'm coming to find that 0.5mm variation in the wheels isn't that big of a deal anyway...because I'm seeing WAY more flex than that from the USB when mounted in the multi-base   

I was really looking forward to how easy this setup was supposed to make it for me to get flat bevels on all my turning tools....but at this point I've gotta say I'm not all that impressed, and am glad I bought the stuff used and didn't pay the full blown retail for most of it 

[Ken S]

I do not believe that Tormek ever intended its machines to be used as surface grinders. Industrial surface grinders can achieve fitness of .0002", much more precise than lathes or milling machines. This level of precision is expensive and skill intensive.

I believe you are correct is saying that the wheel swapping consistency was designed for edge grinding rather than face grinding. For most sharpening, diameter consistency is a real advantage.

While surface grinder precision is not a practical goal, We can certainly make the width of the diamond wheels more consistent. The thread length of the Tormek shaft is long enough that adding a small amount to the spacer does not present a problem. If you measure the thickness of your wheels, using the measurement of your thickest wheel plus around 3mm for a spacer. With your thinner wheels, make the spacer thickness 3mm plus the amount needed to bring that wheel to the same thickness as your thickest wheel. all of your wheel thicknesses should project the same amount.

The original error was the different in wheel thickness plus the play in the multi base. With the thickness variation corrected, you have only the multi base play error. There may be ways to lessen this. This is sharpening, not toolmaking. how much precision is required?

Ken

[Kavik]

Certainly not expecting .0002" here, but I would think better than .02" (.5mm) overall wouldn't be within the realm of the impossible.
If I knew someone with an end mill, i would just have the hubs cut down to equal backspacing and call it a day.  Short of that, yes, custom spacers are still the other option I'm considering.

This is sharpening, not toolmaking. how much precision is required?

For the thousands of dollars many people put into these systems, systems that boast precision and repeatability above all else, i would say "all of it".  All that promised precision is required 
Looking at all the branded and user created jigs, software to measure absolute angles and settings down to fractions of mm and degrees...that almost seems like a silly question lol

Taking the wheel width issue completely out of the equation, this was my issue from this weekend:
I was working on setting a new bevel on a skew chisel. 1/4" thick HSS, with a 30° skew.
Using the SVS50 with the standard USB, on the face of the wheel, the hollow grinding was no problem.  I could flip and grind as many times as needed, and every time it hit perfectly.  In the end, each side had one continuous grind pattern.
Switch to the multi-base and side grinding.... And I've spent ages chasing uneven grinds.  A straight, flat edge, grinding against a flat wheel, and I can't for the life of me get full surface contact in a single pass.  I'm now well beyond the point were I could've done this faster by hand.

Because of the multiple joints, between the multi-base he the USB, it's not just a question of the bar moving closer to the wheel and dropping the angle a bit...that, i could deal with.
Instead, the flex causes twisting in multiple directions.  Wiggle it one way, and the bevel angle changes.  Wiggle it another, and you grind away the tip, or the heel.
And this is with using as light a touch as I can, while holding just tight enough to keep the jig against the bar, and applying just enough pressure to make it cut decently.

Keeping the tool/jig closer to the legs of the USB helps in some regards, as does locking the multi-jig closer to the machine. This is probably why i didn't notice this at first, when using other jigs.  But doing something like a skew chisel only lets you start near the legs for one side...when you flip it, you're now over the (very flexy) far end of the tool rest.

The only way I can think of to resolve all that flex, would be to have a tool rest that is somehow supported on both ends.  Which, of course, would be impractical for every other jig that requires sliding over the bar.

I don't even care about the wheel width issue at this point, but it's driving me bonkers that i can't grind a tool, lift it off the wheel, set it back down without changing anything, and not be grinding on the same plane as I was just seconds earlier.

[cbwx34]

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... software to measure absolute angles and settings down to fractions of mm and degrees...
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I've said for some time now (as have others), this degree of accuracy ain't happenin'. 

Carry on....      

[3D Anvil]

Yes, the precision of this system is somewhat illusory.  You can carefully measure your USB-to-stone/base height to a fraction of a millimeter, but then, when you tighten down the USB screws, the height will change by several millimeters, even if you push down hard on the USB when tightening.