A Faster, More Repeatable Way to Set Up USB Height?

[BeSharp]

SUMMARY: A $50 investment could be a faster, more repeatable way to set Tormek Universal Support Bar ("USB") height. It may not result in "bragging rights" BESS numbers, but I consistently get BESS numbers below 100. 

BACKGROUND

Computer software has taken Tormeks into the 21st Century. I use calipers to set the USB height. However, I was not happy because:

1) Regular calipers are poor depth calipers. The caliper end is barely wide enough to go over the 12mm diameter USB. That is why both my calipers have depth gauge adapters on the ends. However, even after setting them up using a flat reference surface, I found one caliper measuring .1mm short and the other measuring .1mm long.
2) Parallax error. Unless the extended leg is absolutely vertical, the measurement will be too long.
3) Speed - moving the caliper to the desired measurement takes time. My iGaging calipers have what they call "Absolute Origin" - they remember where they are even after shutting off. This helps, but I wanted better.
4) Poor repeatability due to the above three things.
5) Longer USB means larger errors the farther one is away from the two vertical legs. Tormek's new US-430 is 34% longer than the US-105.
Some after-market USB legs are smaller (11.83 mm diameter vs. 12 mm diameter).  Such bars could result in not being parallel with the Tormek's top surface due to play inside the 12mm diameter Tormek leg sleeves.

[BeSharp]

USE INSIDE MEASUREMENT INSTEAD?

I use Australian software. All three (Grinding, Frontal Vertical Base, and Paper Wheel) calculate the USB height to the USB's top.

But what if we measure instead to the USB's bottom? Then we are dealing with an inside measurement.

USB diameter is 12mm. So, all we have to do is subtract 12mm to get the corresponding inside measurement. Simply fill the desired space with the correct spacers (conveniently held down by gravity), and you're done. In contrast to using calipers, the strengths are:

1) Could be more accurate (more on this below)
2) Much less parallax error
3) Faster
4) Easily repeatable
5) Using TWO sets of spacers can help setup a USB parallel to a Tormek's top surface. 

[BeSharp]

SPACERS

Spacer sets, commonly known as gauge block sets, are highly accurate metal blocks that can be stacked together to form your desired spacer. There is virtually zero cumulative error from stacking gauge blocks with flat machined surfaces due to "wringing". (For a fascinating history on gauge blocks, search Mitutoyo's web site for the PDF, "History of The Gage Block" under Literature > Corporate. "Wringing" is explained on page 5).

However, two budget-friendly 102 piece gauge block sets would still cost around $300. So I went for a cheaper solution, comprising of 1-2-3 gauge blocks ($30), a 10mm gauge block ($20), a 1/16" to 1/2" drill bit set in 1/64" increments (already have), and a set of metric feeler gauges (already have). Total outlay: $50. (I have two sets, so my outlay was $100.)

[BeSharp]

METRIC GAUGE BLOCKS

Machinists are familiar with 1-2-3 gauge (setup) blocks - they are precisely machined and ground to have 1" x 2" x 3" sides. Since my software is metric, I bought 25mm-50mm-75mm gauge blocks.

For the last bit of space, I use feeler gauges (0-1.0mm) or, when greater than 1mm, drill bits.

But are 1/64" drill bit increments small enough?

Some of the Australian sharpener's protocols (i.e. for Shun) varies the angle by only .1 degree. His software calculates that to be about .15mm USB height variance (about .00590"). 1/64" = .015625" = about .4mm. So, 1/64" difference translates to .27 degrees difference - too coarse to vary the angle by .1 degree. In other words, using 1/64" incremental drill bits yields .27 degree sharpening angle accuracy. (Metric drill bits go up in .5mm increments = .33 degrees).

Despite this, I found using gauge blocks plus 1/64" increment drill bits seems to yield lower BESS values!

[BeSharp]

REAL LIFE RESULTS

The first picture shows setting up a T7's USB height. Software says 168.89mm to top of USB, so target inside measurement is 168.89mm - 12.00mm = 156.89mm.

The 156.89mm is set with two metric 25-50-75 setup blocks plus a 17/64" drill bit (75mm + 75mm + 6.746mm = 156.75mm). With this spacer combo, it's .14mm too low.

You would think using such drill bits means duller edges. But my experience yields sharper edges. Before, my BESS readings seem to be around 100 (at 15 degrees). Now they seem to be around 80.

I can comfortably say I am not having higher BESS readings using this inside spacer method using 1/64" increment drill bits. In addition, it is faster to setup and much easier to repeat.

[BeSharp]

LABELS

I also made magnetic labels marked with the spacers needed. I can now glance at a machine and immediately see what it is set for. If I need to change the angle I switch labels and adjust the USB height per that label's instructions. No software calculations.

[BeSharp]

USB NOT PARALLEL TO TORMEK TOP

Tormek recommends setting the USB by pressing directly over the threaded leg while tightening the locking screw. Only after that should the other locking screw be tightened. However, some of my Tormek USB have legs that are not square with the top bar. With such USB, the Tormek method does not result in a USB parallel with the Tormek casing top.

Tormek USBs fit tightly into Tormek sleeves. Some aftermarket bars measure smaller - around 11.8 mm instead of 12mm. This means more play (One measured 1.18mm height difference between the two legs that are 90mm apart). This extrapolates to 3.74mm error at that bar's long end.   

The solution: set up using TWO sets of gauge blocks - one set close to the left edge of the Tormek's top, and the other set close to the right edge. Push down on BOTH legs at the same time, then tighten both locking screws (loosen the micro adjust nut(s) first, then snug them down afterwards). This works best on older Tormeks up to T7. The T8 has sloped left and right sides, so you cannot place gauge blocks there. The T8's on/off switch also blocks placing gauge blocks between the two cast leg sleeves.

[BeSharp]

CONCLUSION

This is an alternative, low-cost way to set computerized USB height. I find it is accurate enough for my needs - ensuring the pesky wire edge has been de-rooted (my sharpening business's main selling point is long edge life). However, if one is chasing ultimate "bragging rights" sharpness, then one should invest in a 102 piece gauge block set, or go back to the caliper method.

[Ken S]

USB NOT PARALLEL TO TORMEK TOP

Tormek recommends setting the USB by pressing directly over the threaded leg while tightening the locking screw. Only after that should the other locking screw be tightened. However, some of my Tormek USB have legs that are not square with the top bar. With such USB, the Tormek method does not result in a USB parallel with the Tormek casing top.

Tormek USBs fit tightly into Tormek sleeves. Some aftermarket bars measure smaller - around 11.8 mm instead of 12mm. This means more play (One measured 1.18mm height difference between the two legs that are 90mm apart). This extrapolates to 3.74mm error at that bar's long end.   

The solution: set up using TWO sets of gauge blocks - one set close to the left edge of the Tormek's top, and the other set close to the right edge. Push down on BOTH legs at the same time, then tighten both locking screws (loosen the micro adjust nut(s) first, then snug them down afterwards). This works best on older Tormeks up to T7. The T8 has sloped left and right sides, so you cannot place gauge blocks there. The T8's on/off switch also blocks placing gauge blocks between the two cast leg sleeves.

BSharp,

Your paragraph two answers a question for me. Over the years, I have cut down several SVD-110s into small platforms. One day, I saw a marked down clone platform at a local dealer. It was outside the store as pRt of the sidewalk clearance sale. Before paying for it, I tried it on the support bar of the store demo Tormek. The bore was too small to fit on the Tormek support bar. It was probably made to fit an 11.8mm support bar, a poor design as most of the clones rely on Tormek for most of their jigs.
I would propose a different solution, use only Tormek support bars.

If you have an out of square Tormek support bar, contact support. (support@tormek.se)

All in all, I would say you have put together a very accurate system.

Ken

[Hannsi1957]

please excuse me if i start smiling at your comments. if you are already so meticulous about the whole thing..... maybe you can also tell me the difference in the degree of pain when i cut myself with an exactly 15° ground knife compared to a cut with a 15.05° ground knife? i'm sure you understand what i'm getting at..... you can also exaggerate everything. simple and comprehensible should be the motto. under this aspect, your explanations go absolutely too far for me.
but you have put a lot of thought into it, respect for that.
greetings Hanns

[Ken S]

Hanns, to answer your question, the difference in pain is .05°. I'm not sure what the metric equivalent is.     

Ken

[BeSharp]

please excuse me if i start smiling at your comments. if you are already so meticulous about the whole thing..... maybe you can also tell me the difference in the degree of pain when i cut myself with an exactly 15° ground knife compared to a cut with a 15.05° ground knife? i'm sure you understand what i'm getting at..... you can also exaggerate everything. simple and comprehensible should be the motto. under this aspect, your explanations go absolutely too far for me.
but you have put a lot of thought into it, respect for that.
greetings Hanns

Hanns, I'm not sure if I understand your question. But then, your English is still way better than my German : )

[RickKrung]

CONCLUSION

This is an alternative, low-cost way to set computerized USB height. I find it is accurate enough for my needs - ensuring the pesky wire edge has been de-rooted (my sharpening business's main selling point is long edge life). However, if one is chasing ultimate "bragging rights" sharpness, then one should invest in a 102 piece gauge block set, or go back to the caliper method.

BeSharp,

Very interesting approach.  Congratulations on some innovative thinking.  If I had not already switched to using the direct distance between the USB and the grinding wheels, I'd have to consider your methods for their excellent accuracy and consistency.  I always mark bevels with black marker as a visual check and have found I like accuracy and consistency more because they make the grinding and honing more efficient than for the precision of the final resulting bevel angles.  I have a T8, so I'd have to find alternative methods, given the sloping sides and power switch. 

With all of your machines and even with the use of diamond (and probably CBN) wheels with non-changing diameters, how is your method for "fiddly-ness" setting up the blocks/drills and gages?  Do they tend to topple at all?  Do you have machining capabilities?  If so, I'd consider making some precisely dimensioned single-piece-blocks to replace the 1-2-3 blocks (eg. ganging a set of four aluminum blocks on a mill and flycutting the surfaces exactly the same).  Unless you need the different dimensions of the 1-2-3 blocks for vastly different height settings.

And given your production needs in a business, I would think that a gage block set would prove its value in reducing the time required for set up.  I have such a gage block set, but they are not stainless steel, so I'd be concerned about them getting wet and corroding.  Likewise, I have two sets of gage pins, in 0.001" increments, from 0.625"-.0250" and 0.251"-0.500", which could really dial in your process.

Given your penchant for precision and accuracy and efforts towards parallelism of the USB bar, have you considered how parallel the tops of the machine cases are to the top surface of the grinding wheels?  Since the wheels ride on the shaft of a motor bolted inside the machine case, it is not necessarily a given that the shaft (and thus the wheel grinding surface) is parallel to the top of the machine. 

Again, great thinking,

Rick

[BeSharp]

Rick, the accuracy analysis using drill bits in 1/64" increments was to see if such increments were fine enough for my needs (de-rooting the wire edge) while NOT spending a lot of money. I'm guessing most members, like I, already have a set of drill bits and feeler gauges. I don't want to buy a set of gauge blocks if I don't have to. The conclusion is that, for my needs, I don't. Therefore, pin gages are really unnecessary too. It's good enough. Hopefully other members will conclude that it's good enough for them too.

The whole accuracy thing is not to make sure the angle is exactly 15 degrees versus 15.05 degrees, but to ensure that the edge doesn't get rounded off as it progresses through all the machines. My "rig" is designed for speed. For example, when sharpening Shuns, it goes through 3 grinding wheels on two T7s, 3 paper wheels on two different buffers, and a leather wheel on another T7 with a FVB. Therefore, I need to ensure the sharpening angle is consistent with all the machines. 

As for the degree of "fiddly-ness", that's the whole point. The blocks do not topple (on end they're still 25mm x 50mm).They barely fit between the wheel and the leg sleeves. This is where the T7 is better than a T8. Again, I find this method to be MUCH less fiddly than using calipers. (And larger drill bits are actually easier to work with than small ones!)

Perhaps later I will get some precisely machined custom blocks. But I'm happy with the way it is for now - again, because it's NOT fiddly. (Mitutoyo does make custom length gauge blocks...)

Finally, yes, all the above is based on the assumption that the machine top is parallel with the stone surface. I'm not going to try to address that : )

[Drilon]

 Well, I also have a simple way to get the software readout values for the USB height to the Tormek. As an "anchor" for my depth caliper I use a small Neodym magnet cube with 5,0 mm edge length. On the housing of my T7 it sits firmly as the housing is made of steel (Magnetic_cube_1). On the FVB I had to fix it by a glue as the parts used there are non-magnetic (Magnetic_cube_2).

After setting the desired height on the caliper, which is the software readout minus 5,0 mm edge length of the magnet, I hold the end of the caliper near to the magnet cube and immediately the magnet grabs the end of the caliper. Now I can focus on adjusting the right USB height. Very simple, fast and no need to control marks and parallel lining.

Happy New Year, stay healthy!
Drilon