Using the Variable Thickness Stone Adapters

[tcmeyer]

I’ve reversed my angle bar, so the detents are opposite from where the VSTA clamp screw touches. Even if it wasn’t, the ends of the screws supplied with the VSTA are flat, not cone-shaped. I think this is almost mandatory if you’ve added the locking levers.

Did anybody notice that my left-side locking lever is not in the normal position? About six months ago I had to drill and tap a new hole, because the factory threads stripped. It looks like they’re using oversized drills to make the tapping easier and maybe have gone too far. This aircraft-grade aluminum (at least I think it’s that) is really tough stuff. Thread depth is what limits the tensile load limit for screws and bolts. Usually you can go down to 70% depth and still be workable. Can you feel any wobble in your thumbscrews when they’re not locked down?

RE the AngleCube issue, yes, the VSTA is much, much faster. With the AngleCube, I lower it into position three or four times to get the best reading. If you make small adjustments with the AC in place, it usually won’t even respond. Getting readings of 0.1 degree differences is like eating a soup sandwich; good luck.

[tcmeyer]

I did some testing today, to see how repeatable my technique is with a series of blocks.

The premise of the test is to use the VSTA’s as a reference, making all settings from scratch and measuring the resulting angles.

Qualifier: Be advised that these tests were conducted with modified blocks, using 1/4″ Oilite bronze bearings (bushings). Don’t expect to the get the same results with unmodified blocks.

In each test, I loosened the ball-joint mount from the degree-bar, installed a new stone and then lined the block up with the fixed VSTA plate, then tightened the ball-joint mount to the degree bar. I then following my standard procedure of backing out on the micro-adjusting screw to clear the stone from the VSTA plate, then turned the micro-adjust in while pinching the far end of the stone to the far end of the plate until contact is made and resistance is felt. Each reading was taken with the same amount of pressure applied at the same points.

Before the main part of this test, I ran a series of tests to establish how to take valid angle readings with my AngleCube. With the stone resting against the vise, I took 20 consecutive readings on my AngleCube, raising it and then replacing it against the stone and extracted an average. I did this for two stones, taking 20 readings from sides A & B and another 20 with the stones inverted. Having four sets of samples, I established that the first ten samples in each set were within 0.04 degrees of the 20-sample average. Now I knew that 10 samples were adequate in establishing a reasonably accurate reading.

Next I took 10 sample readings for each of eight different stones. Again, each stone was set up from loose hardware, using the same set-up technique with the VSTA (swat) adapter descibed above.

With the first stone, I took three sets of samples, each with the same set-up procedure. Theoretically, they should all be the same. The first set had an average of 19.90 degrees. The second set was 19.93 degrees and the third set was 20.00 degrees. Statistically, this isn’t a big sample population, but we can infer from this that the VSTA should produce angles within about 0.1 degrees, all else being equal. Eight more stones varying in thickness by up to about 0.030″ produced angles as high as 20.15 degrees. This actually is still pretty impressive. Plus or minus 0.15 degrees or less is pretty darn cool, I think.

As testing continued with the additional stones, I noticed that as the blocks became thinner, the angles tended to increase. This is what the VSTA is suppose to compensate for, so what gives?

More to come… But please, if you have some insight into this, we’re all waiting with bated breath…

[JS]

Was testing done just on the diamonds or other stones as well?

[tcmeyer]

I tested one each of my 400/600 and 800/1000 grit diamond blocks, my 1200/1600 and micro-fine ceramic blocks and several of my home-made glass blocks. The results are logged on an old XP laptop which isn’t connected to my intranet. I’ll have to transfer the Excel file and post it here later.

[JS]

I’m eager to see those results…

[tcmeyer]

As discussed above, I experimented with my VSTA’s using a series of my blocks, all of which have been modified to add bronze bushings to tighten their angular variability.

After my intial testing and comfortable that ten readings would be valid, I then took ten readings of eight blocks, after using the VSTA adapter to set each block to the reference angle.

The readings were as follows:

19.9 19.9 19.9 19.9 19.9 19.9 20.1 19.8
19.95 19.9 19.95 19.95 20 19.9 20.1 19.9
19.95 19.8 20.1 20 20.05 19.85 20.05 19.85
20 19.95 20 19.95 20.05 19.95 20.1 19.8
19.95 19.95 20.05 19.95 20.1 19.9 20.1 19.8
19.95 19.9 20 20 20.05 19.9 20 19.85
19.9 19.9 20 20 20.1 20 20 19.85
19.9 19.9 19.95 19.9 20.1 19.85 20.1 19.75
19.9 19.9 20.05 19.9 20.05 20 20.05 19.85
19.9 20 20 19.95 20 19.95 20.05 19.9

19.93 19.91 20.00 19.95 20.04 19.92 20.07 19.84

Sorry, but the spreadsheet doesn’t copy very well, but you get the drift…

The results show that properly used, the VSTA (SWAT for you old-timers) should produce angles within about 0.23 degrees of each other, or plus/minus 0.115 degrees. If I toss out the last two sets of samples, the range is much better at +/- 0.07 degrees. As for you statistics guys, come on. Lighten up.

Note that each stone was reset to the reference angle with the VSTA, so the variability listed included all the possible contributing factors – The variability in the stone, the execution of the VSTA procedure and the actual taking of readings.

Any questions?

[Mark76]

Wow, interesting experiment! It seems that you can get very accurate results using the VTSA. Particularly since the your measurement results include not only the actual angle differences, but also measurement errors 😉 . (I know how difficult it is to measure a 0.1 degree angle difference with an angle gauge. And these things are accurate up to x only, too.)

Did you include stones in your test set that are much thicker than the stock stones? Like the Chosera’s?

Molecule Polishing: my blog about sharpening with the Wicked Edge

[tcmeyer]

I don’t have any stones that are more than 0.020 or 0.030 different, so I can’t say for sure.

But I did a little checking of the geometry in a simple CAD program. It occurred to me soon after the VSTA came out that the micro adjusts set the offset at about 10 degrees, but the actual difference in thickness showed up at about 20 degrees for most of my sharpenings. In other words, the VSTA was designed to correct for thicknesses in stones used at about 10 degrees. However: large differences in stone thickness could fall outside of the micro-adjust’s range, and require movement in the base at the degree bar, which is not at 10 degrees, but at zero degrees.

Stone thicknesses which were adjusted for within the range of the micro-adjusts – say 1/4″, would result in angular errors of only about 0.10 degrees. Changes in the degree bar setting are done horizontally and don’t account for the angle of the rod. If my method is right, a 1/2″ offset taken in the horizontal axis could produce an error of 0.65 degree for the resultant rod angle. Pretty awful.

A lesson from this? Set-up your VSTA’s with the thinnest of your stones and the micro-adjust’s set near their inboard limit. This would allow you to make whatever adjustments you needed for thicker stones with the micro-adjusts and reduce any geometric errors. You don’t want to use the degree bar as the offset method. So how thick are the Choseras?

So far as I know, this is the first time anybody’s pointed to this problem. Has anybody else noticed this? Am I full of sh__?

[wickededge]

Tom,

Do you still have the original arms from your sharpener with the u-joints? If so, I’d love to see what you observe using the VSTA with those arms.

-Clay

[tcmeyer]

I’ve got the original arms, but I don’t have any original blocks. The idea is interesting, but the original arms are only adjustable in the horizontal axis. I’ll have to at least try it to see how well it works with stones of roughly the same thickness. Maybe later this week.

I don’t know if you picked up on it, but the first three columns of data were using the same stone – just repeating the setting procedure.

Clay: Do you know what the thickness of a Chosera block is? Didja get my gift package yet?

[wickededge]

I’ve got the original arms, but I don’t have any original blocks. The idea is interesting, but the original arms are only adjustable in the horizontal axis. I’ll have to at least try it to see how well it works with stones of roughly the same thickness. Maybe later this week.

I don’t know if you picked up on it, but the first three columns of data were using the same stone – just repeating the setting procedure.

Clay: Do you know what the thickness of a Chosera block is? Didja get my gift package yet?

I think it would be interesting to study the differences of using the VSTA with the original and upgraded arms.

Just got the package now, thanks!

Choseras are 5mm thick.

-Clay

[Gustav Highstein]

First, thanks for your original post. I think it’s very clear and useful.
Would you be able to describe any more precisely how you converted your paddles? What tools you used. etc.? Anything you’re willing to share. I see that you say a little more in reply to another response which is already useful.
It’s very important for me to find a way to add bearings to all of my paddles, but I’m not sure if I will be able to do it myself or whether I will need to find help doing it. I use my tools for work everyday for a micro precision task and if my knives are not “just right” it’s as if they aren’t sharp at all. Other posts about technique have helped me to work around this problem to some degree, but not entirely. So I can’t thank you enough in advance for any help on this issue.

[Gustav Highstein]

Hi TCMEYER,

Thanks again for all the info on this link! I sent you a private message a while ago. I wonder if perhaps you didn’t receive it and therefore am cluttering up this thread with a public/private message asking if you did. Sorry if I’m not using the forum correctly by doing this. If I am, anyone reading this: please feel free to tell me to: DESIST 🙂

[Eamon Mc Gowan]

Hi TCMEYER,

Thanks again for all the info on this link! I sent you a private message a while ago. I wonder if perhaps you didn’t receive it and therefore am cluttering up this thread with a public/private message asking if you did. Sorry if I’m not using the forum correctly by doing this. If I am, anyone reading this: please feel free to tell me to: DESIST 🙂

Gus,
Welcome to the forum! How are you going to figure this thing out if ya don’t ask questions?? I would say your safe to ask away around here. Everyone is always real eager to help the next guy coming along.
It looks like things may have got confused with your PM? TCMEYER is always willing to help. I would wait as he should be along soon and will see this.
Good luck with your WE and remember to always have fun!

[tcmeyer]

Thanks Guys!

I’ve PM’d Gus and must apologize for the error of my ways. When I invited Gus to send me his e-mail address, someone else jumped in ahead of him. Since the name was completely different, I thought it was Gus, and having sent him the requested info, I stopped checking my PM’s.

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