TormekCalc3 - Advanced grinding calculator

[RickKrung]

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4.14mm from the hole edge to the top and 12mm diameter of the hole.
Is that correct? It was not the best measurement
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Thought I might offer some alternative methods for making measurements, ones that I use all the time when "reverse engineering" existing parts that I want to work with and come up with reliable numbers. 

First, with something like an existing hole, I like to make two measurements - to/from opposite sides of the hole to a reference surface and then average the two readings.  They are almost always different, due to measurement/user error.  Having and average of two measurements reduces the effects of those errors.  Your photo shows step one.  For clarity, I show how I measure from the Inside Dimension (ID) to the flat surface.


Measuring to the other side of the hole ID is difficult because when putting one caliper jaw on the opposite inside surface, what to you put the other jaw against?  Clamp a piece of stock to the flat surface that protrudes just enough to get the "insided" caliper jaw against it.


Another way is to take advantage of the shaft being securely inserted into the hole, as in the shaft in the upper part of your photo.  Using the caliper faces on the back side of the caliper head, a very reliable measurement can be made from the flat surface to the close side of the shaft.  Be sure the wider flat/perpendicular face of the caliper jaw is solidly flat on the outside surface of the block. 



The more common, but less reliable method is to use the inside jaws between the shaft and a clamped bar.


For the second measurement, to the opposite side of the shaft, use the inside jaws, in the more familiar manner.


Again, average readings from measurements to each side of the hole. 

I hope this is clear enough and helpful.

Rick

[cbwx34]

@RichColvin! Just a person I need right now. A quick question for you: The VF constant is slightly off in the TormekCalc. I believe it is set for Vadim's VFB. I measured the distance from the center of horizontal support arm to the top of the unit is 10.14mm
...

One thing I noticed is that the edge of the hole appears chamfered?... and it looks like you're measuring to that.

IMO, the best way to measure is with the base setup like you're going to use it... (I'd put the rod back in.)

Also, I noted that your FVB looks slightly different than the one I got early on.  I asked Rich if there was a change in measurements... he said he did make some slight changes, but didn't know if the measurements changed.  I get a different measurement than you (around 6.8 ), so it's possible the one used in the TormekCalc Spreadsheet might have been different.  (Why it's often recommended to measure your own setup.)

[RickKrung]

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One thing I noticed is that the edge of the hole appears chamfered?... and it looks like you're measuring to that.
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I noticed that too and if that is how it was measured, your point is spot on.  It does look like there is about the same amount of gap between the edge of the block and the other jaw, however, so I took it as he had taken the measurement OK, and was just resting the calipers for taking the photo. 


If the picture does show the actual measurement being made, then the calipers are cocked as well, with the jaw back away from the edge of the block, which would add additional error.  Speaks to alternative methods i mention above. 

Rick

[SergeiDubovsky]

Yup. It's not the measurement photo. I just wanted to remember where it was measured and I was lazy to write it down. So I measured an take a picture in general vicinity.

It looks like, I found what was introducing the error into Calc. With measured numbers, the angle matches.
I also tried the Bosch GM220 trick for the USB height setting. It's precise, but it takes time to set the angle on that thing. How lovely would it be if Tormek engraved the ruler onto smooth USB leg.

[cbwx34]

Yup. It's not the measurement photo. I just wanted to remember where it was measured and I was lazy to write it down. So I measured an take a picture in general vicinity.

It looks like, I found what was introducing the error into Calc. With measured numbers, the angle matches.
I also tried the Bosch GM220 trick for the USB height setting. It's precise, but it takes time to set the angle on that thing. How lovely would it be if Tormek engraved the ruler onto smooth USB leg.

Glad you got it working.

Doubt we'd ever see a ruler engraved... too many variables.  Someone in the Tormek group on FB found a machine with one of these hooked up...

https://www.aliexpress.us/item/3256803735396716.html?gatewayAdapt=glo2usa4itemAdapt&_randl_shipto=US

... don't have any details.  (If you join the group and search for "digital" you'll find the thread.)

[RickKrung]

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Perhaps. That height measurement feels bit clumsy. There is no fixed point to measure against. I would gladly pay up for a reliable, fast and easy way to know the support height.

Eons ago when I was still messing with measuring the USB to case height, here is the best solution I had found for making consistent readings.  The depth gauge foot with the angled end spaces the measurement point far away enough from the slope of the case close to the vertical support boss and the top Micro-Adjust nut maintains the calipers parallel to the USB bar. 

Photo shows the depth caliper in position and the two Micro-Adjust nuts, link to the thread provides the discussion. 

Costs involved were the special depth caliper and one more Micro-Adjust nut.  Even so, once I figured out that measuring from the USB direct to the stone/wheel surface was faster, more accurate and universal (applies to vertical or horizontal USB with our without the FVB and to the honing wheels) I've never used the above measurement method again. 

Rick

[RickKrung]

I like Rick's use of a marking gage as a "depth gage" to measure from the top of the support bar to the edge of the grinding wheel. (I call this measurement "Distance" in my PDF describing the kenjig.) The substantial metal rod seems less rickety than the thin flat metal extension on four way calipers. I prefer the larger footprint "gage block" approach of the kenjig, although the adjustability feature of the marking gage is formidable. (Rick, a machined rod with a larger foot would combine the best features of both. Or, perhaps a collar or spacer with an ID matching the diameter of the rod. This would eliminate the need for machining.)

I have always measured from the top of the support bar to the edge of the grinding wheel, as highlighted in yellow in the diagram. I have never thought of it was inaccurate. The flat bottom does not perfectly match the curvature of the grinding wheel; however, I can eyeball matching gaps on both sides. Given the same wheel diameter, it works on my T7 or T8 with no compensation. I have never understand any advantage for measuring to the frame.

Ken

Ken, I am not following the benefit what you are expressing in bolded text above.  I think the 8mm (0.312) dia. rod is about perfect as a "foot" for contacting the wheel surface.  Wider can lead to errors in reading if the corners contact rather than the center.  The key is making sure the shaft is parallel to the line between the USB and axle, which is best shown by the rubber band, rather than eyeballing, IMO. When that is done right, it aligns the contact point to the center of the shaft.  A wider food would only interfere/complicate matters, again IMO.  (The oft referenced rubber band photo).


Rick

[SergeiDubovsky]

here is the best solution I had found for making consistent readings.  The depth gauge foot with the angled end spaces the measurement point far away enough from the slope of the case close to the vertical support boss and the top Micro-Adjust nut maintains the calipers parallel to the USB bar.

https://www.aliexpress.us/item/2251832520112533.html

...or this... https://www.zoro.com/mitutoyo-electronic-digital-depth-gage-0-to-8-in-571-212-30/i/G0321824 if the cheap version works as good as I hope it would

[Sir Amwell]

Please correct me if I'm wrong. Surely the truly accurate way of determining a given bar to stone measurement would be to follow a line to the centre of the shaft? Not ' parallel ' to the rubber band as in the photo?

[Ken S]

Please correct me if I'm wrong. Surely the truly accurate way of determining a given bar to stone measurement would be to follow a line to the centre of the shaft? Not ' parallel ' to the rubber band as in the photo?

You are correct. In this case, I wonder how "truly accurate" we need to be. In my opinion, the minute amount of error introduced with the rubber band is not significant.

Ken

[RickKrung]

Please correct me if I'm wrong. Surely the truly accurate way of determining a given bar to stone measurement would be to follow a line to the centre of the shaft? Not ' parallel ' to the rubber band as in the photo?

You are correct. In this case, I wonder how "truly accurate" we need to be. In my opinion, the minute amount of error introduced with the rubber band is not significant.

Ken

In a totally literal sense, yes.  But in a practical sense, no.  Ran this through a CAD exercise.  The difference is 0.0055" (0.140mm) for a 250mm wheel and 0.0056" (0.142mm) for a 215mm wheel (honing).  That amounts to a maximum difference in angle of 0.11º at 16º .  I doubt that I can set the marking gauge that precisely, so my error could easily be even greater.  I'm quite a detail person, some may call me anal.  It would be easy to add 0.14mm to the distance displayed by the angle app used for setting the marking gauge.  I am not that anal, however. 

Rick

[Ken S]

Rick,

I think we are saying the same thing, although your more technical way seems more impressive. Just my opinion; however, I do think our computers can carry accuracy further than we actually need. this is fine, as long as we remember to keep our expectations reasonable.

Ken

[RickKrung]

We are and we agree.

Rick

[Ken S]

Rick,

What I have not seen with bevel angle accuracy is "within tolerance" or "not within tolerance". As you know, even top quality machinist tools like Starrett are built to certain tolerances. These tolerances are often listed in their catalog. We have tolerances for flatness, parallelism, squareness, thickness, etc. Gage blocks, including angle gage blocks, are available in different precision grades (and prices!). These grades are often called shop floor, tool room, and laboratory. I don't believe an expert machinist or tool maker would ever say "perfectly" whatever. Rather, he would say "within tolerance".

Knives do not have to "mate" with other tools. Sharpness is essential; precision is not so essential. "Sharp" is not a fixed concept. A knife which seems "perfectly sharp" to a home cook making pot roast might seem unacceptably dull to a professional sushi chef.

What to do? We know basic general standards of sharpness. Smoothly cutting copy paper is a standard test, as is cutting a ripe tomato. I believe anyone sharpening for business should establish realistic personal standards. I would not expect the standard for a typical "farmer's market" rapid sharpening job to be the same as what someone paying top dollar to sharpen an expensive custom knife. Each has its own applications.

Ken

[tgbto]

Please correct me if I'm wrong. Surely the truly accurate way of determining a given bar to stone measurement would be to follow a line to the centre of the shaft? Not ' parallel ' to the rubber band as in the photo?

I use the same technique as described by @cbwx34 here. You can get around the problem you mention by measuring the distance to the stone using a point 6mm away from the caliper slider.