YATU: Yet another T-USB jig

[aquataur]

FYI.
This is a very easy jig that lets me precisely set a certain angle by adjusting the distance from the top of the USB bar to the wheel (hereabouts known as "T-USB" - hence the name), according to the output of any of the simple, but most potent calculators provided here.

It can be realized easily without specialized tools, although a 3D-printer is pure luxury.

You could however make the same thing using a piece of hard wood or plastic or similar, with little more effort.

The idea is based on Perra´s T-Cube, and indeed this unit can be put to good use together with the described jig.

I found that the T-Cube probably excels at using a digital inclination measuring device, and while it may have several other uses (probably not discovered yet), it is not optimal for setting T-USB. If you use it like depicted by resting the bracket on the back side against the USB as shown in pic7, then a (possibly small) error is introduced by measuring the distance at the side of the USB (introducing an offset of 6mm from the USB´s centerline) down to the stone´s perimeter (T-USB is specified as the top of the USB to the stone measured through the USB´s center). Apart from this, one hand is blocked by having to hold onto the jig. The next question is, where does the ruler touch the stone.

So I realized that the ruler should really be 90° rotated and start with "0" flush with the USB´s top down.

I borrowed the mounting of the ruler from Perra´s T-Cube; a slot and a screw. Differently however, the ruler is not intended to ever move in there. This is just a convenient receptacle. The ruler has its last > 12mm sawn off, so that it fits into the fixture. Its length is designed in a way that the ruler, inserted to 5,0 cm, displays the exact distance from top of USB. There is no magic to that number, it could be made shorter, but I found T-USB numbers below 7cm useless.
I chopped the ruler off at 15cm, which promises a great span of projection distance vs. wheel diameter vs. angles.

The earlier printed T-Cube can be made to reside on top of the wheel to the side loosely, so that it rides up and down with gravity when changing the USB´s height, giving the exact reading on its edge.

Thanks to a snug fit of the 12mm bore the jig stays put in any position. Should this joint eventually become loose by frequent usage, a screw could be incorporated like the one that is there.

The ruler of course has to point perfectly towards the center of the wheel, and once you are close to the final destination, this should be re-checked. You could alternatively (as already adressed somewhere) use a rubber band around the wheel hub towards the ruler to center it automatically.

The reading you make on the moving part´s edge is then always guaranteed to refer to the wheel´s apex.

My friend is an expert to 3D printing (you would think this were a sunday afternoon walk for him, watching him). He says even a M8 nut is lousy to print on a 3D printer and of doubtful longevity, so he inserts a slot for a metal M8 nut as depicted in the detail picture. Brilliant.

Hope this is of use for somebody.
-Helmut

[tgbto]

Hey, this is brillant! So if I understand correctly you're measuring 90mm TUSB on the first picture ?

I'm wondering whether a version with a slightly wider red cube and two ball bearings would make it even easier to use ?

[aquataur]

So if I understand correctly you're measuring 90mm TUSB on the first picture ?

No. The ruler displays the true distance from the outmost point of the 12mm rod. If the ruler is correctly aimed towards the hub, then this coincides with T-USB.

So what you are interested in is where the wheel´s apex aligns with the ruler. Since the markings are on the side of the ruler and the apex is in its center (and thus obscured by the ruler), the red "slider" always displays the correct value of the apex - on the bottom side of the red thing.

In the picture the value will be close to 11. This is of course a non-realistic setting chosen to demonstrate the principle.

I'm wondering whether a version with a slightly wider red cube and two ball bearings would make it even easier to use ?

You mean to achieve a perpendicular alignment of the ruler, sort of auto-alignment?
This would work, but I suspect only for a certain wheel diameter, caused by the fixed distance of the rollers. In all other cases, the red cube would either not go down far enough or the rollers would dangle in the air. If you find a fix for that, let us know.

Some kind of a rubber-band towards the hub would do the same, if desired.
In both cases the 12mm bore would need to be rather loose.
I don´t know if the effort pays.

Attached is a picture of a bare bone usage. The red cube is not strictly needed, but the way the scale is marked introduces a bit of guesswork as to what the apex reads.

On the second picture the red cube has been rotated 180°. The nose has no function other than being in the way in this usage. The arrows clearly show the nearly 2mm of difference between the reading where the stone´s circumference meets the ruler and the apex reading. Naturally, this is worst on the small wheel.

[cbwx34]

...

I'm wondering whether a version with a slightly wider red cube and two ball bearings would make it even easier to use ?

You mean to achieve a perpendicular alignment of the ruler, sort of auto-alignment?
This would work, but I suspect only for a certain wheel diameter, caused by the fixed distance of the rollers. In all other cases, the red cube would either not go down far enough or the rollers would dangle in the air. If you find a fix for that, let us know.
...

I thought that was one point of the TTS-100...

The TTS-100 Turning Tool Setter works independently of the diameter of the grinding wheel. You always get the same bevel angle – even if your grindstone gets worn smaller over time. So you can also use the turning tool setter when setting the bevel angle on the honing wheel.

Here it is in action...

[aquataur]

the TTS-100 Turning Tool Setter works independently of the diameter of the grinding wheel.

The TTS-100 does what it promises no doubt.
I did not look into this device, but it is obvious what the two rollers do:
Those are two points forming a secant on the circle of the wheel. The line inbetween them is always perpendicular to the line between the apex (halfway between those points) and the center of the circle.

The TTS-100 must use this effect to achieve its designated purpose. Akin to all the calculators it must use plain trigonometry cast into hardware.

As @tgbto mentioned correctly, a swing like this could be made to help align the YATU towards the center, but solely adding two rollers to each side of the red cube (along the circumference) will either hinder the latter from reaching the stone (if the rollers are too close) or be ineffective when the red cube touches the stone (if the rollers are too far apart).

So the roller - swing cannot be physically connected to the red cube, if you want the red cube to give you the correct distance to the apex (provided the ruler is aimed to the center...). Like the rollers themselves, this would need to be low-friction or it will not settle correctly.  In fact even the part attached to the USB would probably need to be low friction. The roller-swing would need to be touching the stone permanently, independent of the red cube´s position.

Deviating the ruler from the line towards the center has less effect on the ruler´s reading than one would think.

So this stunt is doable, but the effort is enormous compared to the simplicity of the YATU, with a little gain in comfort, no gain in accuracy, and a great gain in complexity (=loss of "make-ability").

[cbwx34]

Good point(s)

[aquataur]

This thing is actually nothing more than a twisted caliper.
Stock calipers measure an outside dimension, and on the back side they usually have some crippled flanges that measure inside, but what we have here is a combination of both:

the gadget measures the distance from the 12mm hole (resp. shaft) (outside measurement) to the stone´s surface (inside measurement).

If such a thing were available then - go for it...

[ArtOfSharp]

I like the idea for the slot for sliding in a nut, it save having to worry about a bolt stripping the thread made in plastic.

However, im not so sure that measuring through the centre of the USB is accurate method, or how turning the ruler system 90 degrees would be accurate with that 90 degree turn.

If i could have the best of both worlds it would be the t-cube with the slot for the nut.

[cbwx34]

...
However, im not so sure that measuring through the centre of the USB is accurate method, or how turning the ruler system 90 degrees would be accurate with that 90 degree turn.
...

The answer given in most of the calculator apps, is a straight line measuring from the top of the USB straight to the wheel.  So, in theory, unless I'm misreading your post, the setup would be more accurate than a caliper or similar method, although the difference is insignificant.

That being the case, I don't see how the "90 deg. turn" would matter either.